Laura Attardi

All Publications

• p53 promotes revival stem cells in the regenerating intestine after severe radiation injury. Nature communications Morral, C., Ayyaz, A., Kuo, H. C., Fink, M., Verginadis, I. I., Daniel, A. R., Burner, D. N., Driver, L. M., Satow, S., Hasapis, S., Ghinnagow, R., Luo, L., Ma, Y., Attardi, L. D., Koumenis, C., Minn, A. J., Wrana, J. L., Lee, C. L., Kirsch, D. G. 2024; 15 (1): 3018

  Abstract

  Ionizing radiation induces cell death in the gastrointestinal (GI) epithelium by activating p53. However, p53 also prevents animal lethality caused by radiation-induced acute GI syndrome. Through single-cell RNA-sequencing of the irradiated mouse small intestine, we find that p53 target genes are specifically enriched in regenerating epithelial cells that undergo fetal-like reversion, including revival stem cells (revSCs) that promote animal survival after severe damage of the GI tract. Accordingly, in mice with p53 deleted specifically in the GI epithelium, ionizing radiation fails to induce fetal-like revSCs. Using intestinal organoids, we show that transient p53 expression is required for the induction of revival stem cells and is controlled by an Mdm2-mediated negative feedback loop. Together, our findings reveal that p53 suppresses severe radiation-induced GI injury by promoting fetal-like reprogramming of irradiated intestinal epithelial cells.

  View details for DOI 10.1038/s41467-024-47124-8

  View details for PubMedID 38589357

  View details for PubMedCentralID 8082264

• Epigenetic priming targets tumor heterogeneity to shift transcriptomic phenotype of pancreatic ductal adenocarcinoma towards a Vitamin D susceptible state. Cell death & disease He, B., Stoffel, L., He, C. J., Cho, K., Li, A. M., Jiang, H., Flowers, B. M., Nguyen, K. T., Wang, K. W., Zhao, A. Y., Zhou, M. N., Ferreira, S., Attardi, L. D., Ye, J. 2024; 15 (1): 89

  Abstract

  As a highly heterogeneous tumor, pancreatic ductal adenocarcinoma (PDAC) exhibits non-uniform responses to therapies across subtypes. Overcoming therapeutic resistance stemming from this heterogeneity remains a significant challenge. Here, we report that Vitamin D-resistant PDAC cells hijacked Vitamin D signaling to promote tumor progression, whereas epigenetic priming with glyceryl triacetate (GTA) and 5-Aza-2'-deoxycytidine (5-Aza) overcame Vitamin D resistance and shifted the transcriptomic phenotype of PDAC toward a Vitamin D-susceptible state. Increasing overall H3K27 acetylation with GTA and reducing overall DNA methylation with 5-Aza not only elevated the Vitamin D receptor (VDR) expression but also reprogrammed the Vitamin D-responsive genes. Consequently, Vitamin D inhibited cell viability and migration in the epigenetically primed PDAC cells by activating genes involved in apoptosis as well as genes involved in negative regulation of cell proliferation and migration, while the opposite effect of Vitamin D was observed in unprimed cells. Studies in genetically engineered mouse PDAC cells further validated the effects of epigenetic priming for enhancing the anti-tumor activity of Vitamin D. Using gain- and loss-of-function experiments, we further demonstrated that VDR expression was necessary but not sufficient for activating the favorable transcriptomic phenotype in respond to Vitamin D treatment in PDAC, highlighting that both the VDR and Vitamin D-responsive genes were prerequisites for Vitamin D response. These data reveal a previously undefined mechanism in which epigenetic state orchestrates the expression of both VDR and Vitamin D-responsive genes and determines the therapeutic response to Vitamin D in PDAC.

  View details for DOI 10.1038/s41419-024-06460-9

  View details for PubMedID 38272889

  View details for PubMedCentralID 5858034

• Targeting p53 gain-of-function activity in cancer therapy: a cautionary tale. Cell death and differentiation Attardi, L. D., Boutelle, A. M. 2023

  View details for DOI 10.1038/s41418-023-01253-7

  View details for PubMedID 38151545

  View details for PubMedCentralID 7954925

• NF1 MUTATION IN OLIGODENDROCYTE PRECURSOR CELLS INDUCES PRENEOPLASTIC LESIONS IN THE BRAIN Pan, Y., Hysinger, J., Yalcin, B., Lennon, J., Raghavan, P., Schindler, N., Anastasaki, C., Chatterjee, J., Mount, C., Nagaraja, S., Scheaffer, S., Attardi, L., Gutmann, D., Monje, M. OXFORD UNIV PRESS INC. 2023

  View details for Web of Science ID 001115245401369

• Tissue-regeneration program underlies lung-cancer suppression NATURE Attardi, L. D., Kaiser, A. M. 2023

  View details for DOI 10.1038/d41586-023-02025-6

  View details for Web of Science ID 001038056400005

  View details for PubMedID 37468810

  View details for PubMedCentralID 5659188

• p53 governs an AT1 differentiation programme in lung cancer suppression. Nature Kaiser, A. M., Gatto, A., Hanson, K. J., Zhao, R. L., Raj, N., Ozawa, M. G., Seoane, J. A., Bieging-Rolett, K. T., Wang, M., Li, I., Trope, W. L., Liou, D. Z., Shrager, J. B., Plevritis, S. K., Newman, A. M., Van Rechem, C., Attardi, L. D. 2023

  Abstract

  Lung cancer is the leading cause of cancer deaths worldwide1. Mutations in the tumour suppressor gene TP53 occur in 50% of lung adenocarcinomas (LUADs) and are linked to poor prognosis1-4, but how p53 suppresses LUAD development remains enigmatic. We show here that p53 suppresses LUAD by governing cell state, specifically by promoting alveolar type 1 (AT1) differentiation. Using mice that express oncogenic Kras and null, wild-type or hypermorphic Trp53 alleles in alveolar type 2 (AT2) cells, we observed graded effects of p53 on LUAD initiation and progression. RNA sequencing and ATAC sequencing of LUAD cells uncovered a p53-induced AT1 differentiation programme during tumour suppression in vivo through direct DNA binding, chromatin remodelling and induction of genes characteristic of AT1 cells. Single-cell transcriptomics analyses revealed that during LUAD evolution, p53 promotes AT1 differentiation through action in a transitional cell state analogous to a transient intermediary seen during AT2-to-AT1 cell differentiation in alveolar injury repair. Notably, p53 inactivation results in the inappropriate persistence of these transitional cancer cells accompanied by upregulated growth signalling and divergence from lung lineage identity, characteristics associated with LUAD progression. Analysis of Trp53 wild-type and Trp53-null mice showed that p53 also directs alveolar regeneration after injury by regulating AT2 cell self-renewal and promoting transitional cell differentiation into AT1 cells. Collectively, these findings illuminate mechanisms of p53-mediated LUAD suppression, in which p53 governs alveolar differentiation, and suggest that tumour suppression reflects a fundamental role of p53 in orchestrating tissue repair after injury.

  View details for DOI 10.1038/s41586-023-06253-8

  View details for PubMedID 37468633

  View details for PubMedCentralID 4231481

• Multifaceted role for p53 in pancreatic cancer suppression. Proceedings of the National Academy of Sciences of the United States of America Mello, S. S., Flowers, B. M., Mazur, P. K., Lee, J. J., Müller, F., Denny, S. K., Ferreira, S., Hanson, K., Kim, S. K., Greenleaf, W. J., Wood, L. D., Attardi, L. D. 2023; 120 (10): e2211937120

  Abstract

  The vast majority of human pancreatic ductal adenocarcinomas (PDACs) harbor TP53 mutations, underscoring p53's critical role in PDAC suppression. PDAC can arise when pancreatic acinar cells undergo acinar-to-ductal metaplasia (ADM), giving rise to premalignant pancreatic intraepithelial neoplasias (PanINs), which finally progress to PDAC. The occurrence of TP53 mutations in late-stage PanINs has led to the idea that p53 acts to suppress malignant transformation of PanINs to PDAC. However, the cellular basis for p53 action during PDAC development has not been explored in detail. Here, we leverage a hyperactive p53 variant-p5353,54-which we previously showed is a more robust PDAC suppressor than wild-type p53, to elucidate how p53 acts at the cellular level to dampen PDAC development. Using both inflammation-induced and KRASG12D-driven PDAC models, we find that p5353,54 both limits ADM accumulation and suppresses PanIN cell proliferation and does so more effectively than wild-type p53. Moreover, p5353,54 suppresses KRAS signaling in PanINs and limits effects on the extracellular matrix (ECM) remodeling. While p5353,54 has highlighted these functions, we find that pancreata in wild-type p53 mice similarly show less ADM, as well as reduced PanIN cell proliferation, KRAS signaling, and ECM remodeling relative to Trp53-null mice. We find further that p53 enhances chromatin accessibility at sites controlled by acinar cell identity transcription factors. These findings reveal that p53 acts at multiple stages to suppress PDAC, both by limiting metaplastic transformation of acini and by dampening KRAS signaling in PanINs, thus providing key new understanding of p53 function in PDAC.

  View details for DOI 10.1073/pnas.2211937120

  View details for PubMedID 36848578

• Understanding the Arf-p53 axis in PDAC suppression Attardi, L. D., Flowers, B. M., Hanson, K., Mulligan, A. S., Ferreira, S., Bhattacharyya, S., Vogel, H., Wood, L. D., Sherman, M. AMER ASSOC CANCER RESEARCH. 2022: 33-34

  View details for Web of Science ID 000899825600039

• Characterizing acinar cell and ductal cell derived PDACs in mouse models Ferreira, S., Flowers, B. M., Hanson, K. J., Gatto, A., Bhattacharyya, S., Sherman, M. H., Attardi, L. D. AMER ASSOC CANCER RESEARCH. 2022: 40-41

  View details for Web of Science ID 000899825600048

• The p53 Transactivation Domain 1-Dependent Response to Acute DNA Damage in Endothelial Cells Protects against Radiation-Induced Cardiac Injury. Radiation research Kuo, H., Luo, L., Ma, Y., Williams, N. T., da Silva Campos, L., Attardi, L. D., Lee, C., Kirsch, D. G. 2022

  Abstract

  Thoracic radiation therapy can cause endothelial injury in the heart, leading to cardiac dysfunction and heart failure. Although it has been demonstrated that the tumor suppressor p53 functions in endothelial cells to prevent the development of radiation-induced myocardial injury, the key mechanism(s) by which p53 regulates the radiosensitivity of cardiac endothelial cells is not completely understood. Here, we utilized genetically engineered mice that express mutations in p53 transactivation domain 1 (TAD1) (p5325,26) or mutations in p53 TAD1 and TAD2 (p5325,26,53,54) specifically in endothelial cells to study the p53 transcriptional program that protects cardiac endothelial cells from ionizing radiation in vivo. p5325,26,53,54 loses the ability to drive transactivation of p53 target genes after irradiation while p5325,26 can induce transcription of a group of non-canonical p53 target genes, but not the majority of classic radiation-induced p53 targets critical for p53-mediated cell cycle arrest and apoptosis. After 12 Gy whole-heart irradiation, we found that both p5325,26 and p5325,26,53,54 sensitized mice to radiation-induced cardiac injury, in contrast to wild-type p53. Histopathological examination suggested that mutation of TAD1 contributes to myocardial necrosis after whole-heart irradiation, while mutation of both TAD1 and TAD2 abolishes the ability of p53 to prevent radiation-induced heart disease. Taken together, our results show that the transcriptional program downstream of p53 TAD1, which activates the acute DNA damage response after irradiation, is necessary to protect cardiac endothelial cells from radiation injury in vivo.

  View details for DOI 10.1667/RADE-22-00001.1

  View details for PubMedID 35512345

• The Mettl3 epitranscriptomic writer amplifies p53 stress responses. Molecular cell Raj, N., Wang, M., Seoane, J. A., Zhao, R. L., Kaiser, A. M., Moonie, N. A., Demeter, J., Boutelle, A. M., Kerr, C. H., Mulligan, A. S., Moffatt, C., Zeng, S. X., Lu, H., Barna, M., Curtis, C., Chang, H. Y., Jackson, P. K., Attardi, L. D. 2022

  Abstract

  The p53 transcription factor drives anti-proliferative gene expression programs in response to diverse stressors, including DNA damage and oncogenic signaling. Here, we seek to uncover new mechanisms through which p53 regulates gene expression using tandem affinity purification/mass spectrometry to identify p53-interacting proteins. This approach identified METTL3, an m6A RNA-methyltransferase complex (MTC) constituent, as a p53 interactor. We find that METTL3 promotes p53 protein stabilization and target gene expression in response to DNA damage and oncogenic signals, by both catalytic activity-dependent and independent mechanisms. METTL3 also enhances p53 tumor suppressor activity in invivo mouse cancer models and human cancer cells. Notably, METTL3 only promotes tumor suppression in the context of intact p53. Analysis of human cancer genome data further supports the notion that the MTC reinforces p53 function in human cancer. Together, these studies reveal a fundamental role for METTL3 in amplifying p53 signaling in response to cellular stress.

  View details for DOI 10.1016/j.molcel.2022.04.010

  View details for PubMedID 35512709

• The role of p53 in the development of pancreatic ductal adenocarcinoma. Hanson, K. J., Flowers, B. M., Hughes, N., Vogel, H., Cong, L., Attardi, L. D. AMER ASSOC CANCER RESEARCH. 2021: 58

  View details for Web of Science ID 000720117400098

• A Balancing Act: p53 Activity from Tumor Suppression to Pathology and Therapeutic Implications. Annual review of pathology Wang, M., Attardi, L. D. 2021

  Abstract

  TP53, encoding the p53 transcription factor, is the most frequently mutated tumor suppressor gene across all human cancer types. While p53 has long been appreciated to induce antiproliferative cell cycle arrest, apoptosis, and senescence programs in response to diverse stress signals, various studies in recent years have revealed additional important functions for p53 that likely also contribute to tumor suppression, including roles in regulating tumor metabolism, ferroptosis, signaling in the tumor microenvironment, and stem cell self-renewal/differentiation. Not only does p53 loss or mutation cause cancer, but hyperactive p53 also drives various pathologies, including developmental phenotypes, premature aging, neurodegeneration, and side effects of cancer therapies. These findings underscore the importance of balanced p53 activity and influence our thinking of how to best develop cancer therapies based on modulating the p53 pathway. Expected final online publication date for the Annual Review of Pathology: Mechanisms of Disease, Volume 17 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

  View details for DOI 10.1146/annurev-pathol-042320-025840

  View details for PubMedID 34699262

• Zmat3 splices together p53-dependent tumor suppression MOLECULAR & CELLULAR ONCOLOGY Bieging-Rolett, K. T., Attardi, L. D. 2021

  View details for DOI 10.1080/23723556.2021.1898523

  View details for Web of Science ID 000646838400001

• Zmat3 splices together p53-dependent tumor suppression. Molecular & cellular oncology Bieging-Rolett, K. T., Attardi, L. D. 2021; 8 (3): 1898523

  Abstract

  The tumor protein p53 (TP53, best known as p53) transcription factor is a critical tumor suppressor, but those p53-inducible genes most important for tumor suppression have remained unclear. Using unbiased RNA interference and CRISPR (Clustered Regularly Interspersed Palindromic Repeats)/Cas9 (CRISPR-associated protein 9) screens, genetically engineered mouse models, human cancer genome analysis, and integrative eCLIP-sequencing and RNA-sequencing analyses, we reveal a new branch of p53-mediated tumor suppression involving the RNA splicing regulator Zinc finger Matrin-type 3, Zmat3.

  View details for DOI 10.1080/23723556.2021.1898523

  View details for PubMedID 34027039

  View details for PubMedCentralID PMC8128213

• An anterograde pathway for sensory axon degeneration gated by a cytoplasmic action of the transcriptional regulator P53. Developmental cell Simon, D. J., Belsky, D. M., Bowen, M. E., Ohn, C. Y., O'Rourke, M. K., Shen, R., Kim, G., Pitts, J., Attardi, L. D., Tessier-Lavigne, M. 2021; 56 (7): 976

  Abstract

  Axon remodeling through sprouting and pruning contributes to the refinement of developing neural circuits. A prominent example is the pruning of developing sensory axons deprived of neurotrophic support, which is mediated by a caspase-dependent (apoptotic) degeneration process. Distal sensory axons possess a latent apoptotic pathway, but a cell body-derived signal that travels anterogradely down the axon is required for pathway activation. The signaling mechanisms that underlie this anterograde process are poorly understood. Here, we show that the tumor suppressor P53 is required for anterograde signaling. Interestingly loss of P53 blocks axonal but not somatic (i.e., cell body) caspase activation. Unexpectedly, P53 does not appear to have an acute transcriptional role in this process and instead appears to act in the cytoplasm to directly activate the mitochondrial apoptotic pathway in axons. Our data support the operation of a cytoplasmic role for P53 in the anterograde death of developing sensory axons.

  View details for DOI 10.1016/j.devcel.2021.03.011

  View details for PubMedID 33823136

• Cell of Origin Influences Pancreatic Cancer Subtype CANCER DISCOVERY Flowers, B. M., Xu, H., Mulligan, A. S., Hanson, K. J., Seoane, J. A., Vogel, H., Curtis, C., Wood, L. D., Attardi, L. D. 2021; 11 (3): 660–77

  View details for DOI 10.1158/2159-8290.CD-20-0633

  View details for Web of Science ID 000625890400028

• Cell of Origin Influences Pancreatic Cancer Subtype. Cancer discovery Flowers, B. M., Xu, H., Mulligan, A. S., Hanson, K. J., Seoane, J. A., Vogel, H., Curtis, C., Wood, L. D., Attardi, L. D. 2021; 11 (3): 660-677

  Abstract

  Pancreatic ductal adenocarcinoma (PDAC) is a deadly disease with a 5-year survival rate of approximately 9%. An improved understanding of PDAC initiation and progression is paramount for discovering strategies to better detect and combat this disease. Although transcriptomic analyses have uncovered distinct molecular subtypes of human PDAC, the factors that influence subtype development remain unclear. Here, we interrogate the impact of cell of origin and different Trp53 alleles on tumor evolution, using a panel of tractable genetically engineered mouse models. Oncogenic KRAS expression, coupled with Trp53 deletion or point mutation, drives PDAC from both acinar and ductal cells. Gene-expression analysis reveals further that ductal cell-derived and acinar cell-derived tumor signatures are enriched in basal-like and classical subtypes of human PDAC, respectively. These findings highlight cell of origin as one factor that influences PDAC molecular subtypes and provide insight into the fundamental impact that the very earliest events in carcinogenesis can have on cancer evolution. SIGNIFICANCE: Although human PDAC has been classified into different molecular subtypes, the etiology of these distinct subtypes remains unclear. Using mouse genetics, we reveal that cell of origin is an important determinant of PDAC molecular subtype. Deciphering the biology underlying pancreatic cancer subtypes may reveal meaningful distinctions that could improve clinical intervention.This article is highlighted in the In This Issue feature, p. 521.

  View details for DOI 10.1158/2159-8290.CD-20-0633

  View details for PubMedID 34009137

• p53 and Tumor Suppression: It Takes a Network. Trends in cell biology Boutelle, A. M., Attardi, L. D. 2021

  Abstract

  The TP53 tumor suppressor is the most frequently mutated gene in human cancer. p53 suppresses tumorigenesis by transcriptionally regulating a network of target genes that play roles in various cellular processes. Though originally characterized as a critical regulator for responses to acute DNA damage (activation of apoptosis and cell cycle arrest), recent studies have highlighted new pathways and transcriptional targets downstream of p53 regulating genomic integrity, metabolism, redox biology, stemness, and non-cell autonomous signaling in tumor suppression. Here, we summarize our current understanding of p53-mediated tumor suppression, situating recent findings from mouse models and unbiased screens in the context of previous studies and arguing for the importance of the pleiotropic effects of the p53 transcriptional network in inhibiting cancer.

  View details for DOI 10.1016/j.tcb.2020.12.011

  View details for PubMedID 33518400

• P53 orchestrates a complex symphony of cellular processes during oncosuppression MOLECULAR & CELLULAR ONCOLOGY Valente, L. J., Attardi, L. D. 2021

  View details for DOI 10.1080/23723556.2020.1852066

  View details for Web of Science ID 000607285300001

• P53 orchestrates a complex symphony of cellular processes during oncosuppression. Molecular & cellular oncology Valente, L. J., Attardi, L. D. 2021; 8 (1): 1852066

  Abstract

  We recently showed that the p53 tumor suppressor simultaneously governs numerous cellular processes in one model of transformation suppression. These findings suggest that p53-mediated tumor suppression relies on coordinated modulation of diverse cellular functions in a particular context, helping to explain why loss of the TP53 (tumor protein p53) gene is so prevalent in human cancers.

  View details for DOI 10.1080/23723556.2020.1852066

  View details for PubMedID 33553606

  View details for PubMedCentralID PMC7849744

• p53 is a central regulator driving neurodegeneration caused by C9orf72 poly(PR). Cell Maor-Nof, M. n., Shipony, Z. n., Lopez-Gonzalez, R. n., Nakayama, L. n., Zhang, Y. J., Couthouis, J. n., Blum, J. A., Castruita, P. A., Linares, G. R., Ruan, K. n., Ramaswami, G. n., Simon, D. J., Nof, A. n., Santana, M. n., Han, K. n., Sinnott-Armstrong, N. n., Bassik, M. C., Geschwind, D. H., Tessier-Lavigne, M. n., Attardi, L. D., Lloyd, T. E., Ichida, J. K., Gao, F. B., Greenleaf, W. J., Yokoyama, J. S., Petrucelli, L. n., Gitler, A. D. 2021

  Abstract

  The most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is a GGGGCC repeat expansion in the C9orf72 gene. We developed a platform to interrogate the chromatin accessibility landscape and transcriptional program within neurons during degeneration. We provide evidence that neurons expressing the dipeptide repeat protein poly(proline-arginine), translated from the C9orf72 repeat expansion, activate a highly specific transcriptional program, exemplified by a single transcription factor, p53. Ablating p53 in mice completely rescued neurons from degeneration and markedly increased survival in a C9orf72 mouse model. p53 reduction also rescued axonal degeneration caused by poly(glycine-arginine), increased survival of C9orf72 ALS/FTD-patient-induced pluripotent stem cell (iPSC)-derived motor neurons, and mitigated neurodegeneration in a C9orf72 fly model. We show that p53 activates a downstream transcriptional program, including Puma, which drives neurodegeneration. These data demonstrate a neurodegenerative mechanism dynamically regulated through transcription-factor-binding events and provide a framework to apply chromatin accessibility and transcription program profiles to neurodegeneration.

  View details for DOI 10.1016/j.cell.2020.12.025

  View details for PubMedID 33482083

• A p53-dependent translational program directs tissue-selective phenotypes in a model of ribosomopathies. Developmental cell Tiu, G. C., Kerr, C. H., Forester, C. M., Krishnarao, P. S., Rosenblatt, H. D., Raj, N., Lantz, T. C., Zhulyn, O., Bowen, M. E., Shokat, L., Attardi, L. D., Ruggero, D., Barna, M. 2021

  Abstract

  In ribosomopathies, perturbed expression of ribosome components leads to tissue-specific phenotypes. What accounts for such tissue-selective manifestations as a result of mutations in the ribosome, a ubiquitous cellular machine, has remained a mystery. Combining mouse genetics and in vivo ribosome profiling, we observe limb-patterning phenotypes in ribosomal protein (RP) haploinsufficient embryos, and we uncover selective translational changes of transcripts that controlling limb development. Surprisingly, both loss of p53, which is activated by RP haploinsufficiency, and augmented protein synthesis rescue these phenotypes. These findings are explained by the finding that p53 functions as a master regulator of protein synthesis, at least in part, through transcriptional activation of 4E-BP1. 4E-BP1, a key translational regulator, in turn, facilitates selective changes in the translatome downstream of p53, and this thereby explains how RP haploinsufficiency may elicit specificity to gene expression. These results provide an integrative model to help understand how in vivo tissue-specific phenotypes emerge in ribosomopathies.

  View details for DOI 10.1016/j.devcel.2021.06.013

  View details for PubMedID 34242585

• The HIF target MAFF promotes tumor invasion and metastasis through IL11 and STAT3 signaling. Nature communications Moon, E. J., Mello, S. S., Li, C. G., Chi, J., Thakkar, K., Kirkland, J. G., Lagory, E. L., Lee, I. J., Diep, A. N., Miao, Y., Rafat, M., Vilalta, M., Castellini, L., Krieg, A. J., Graves, E. E., Attardi, L. D., Giaccia, A. J. 2021; 12 (1): 4308

  Abstract

  Hypoxia plays a critical role in tumor progression including invasion and metastasis. To determine critical genes regulated by hypoxia that promote invasion and metastasis, we screen fifty hypoxia inducible genes for their effects on invasion. In this study, we identify v-maf musculoaponeurotic fibrosarcoma oncogene homolog F (MAFF) as a potent regulator of tumor invasion without affecting cell viability. MAFF expression is elevated in metastatic breast cancer patients and is specifically correlated with hypoxic tumors. Combined ChIP- and RNA-sequencing identifies IL11 as a direct transcriptional target of the heterodimer between MAFF and BACH1, which leads to activation of STAT3 signaling. Inhibition of IL11 results in similar levels of metastatic suppression as inhibition of MAFF. This study demonstrates the oncogenic role of MAFF as an activator of the IL11/STAT3 pathways in breast cancer.

  View details for DOI 10.1038/s41467-021-24631-6

  View details for PubMedID 34262028

• Puma- and Caspase9-mediated apoptosis is dispensable for p53-driven neural crest-based developmental defects. Cell death and differentiation Bowen, M. E., Mulligan, A. S., Sorayya, A. n., Attardi, L. D. 2021

  Abstract

  Inappropriate activation of the p53 transcription factor is thought to contribute to the developmental phenotypes in a range of genetic syndromes. Whether p53 activation drives these developmental phenotypes by triggering apoptosis, cell cycle arrest, or other p53 cellular responses, however, has remained elusive. As p53 hyperactivation in embryonic neural crest cells (NCCs) drives a number of phenotypes, including abnormal craniofacial and neuronal development, we investigate the basis for p53 action in this context. We show that p53-driven developmental defects are associated with the induction of a robust pro-apoptotic transcriptional signature. Intriguingly, however, deleting Puma or Caspase9, which encode key components of the intrinsic apoptotic pathway, does not rescue craniofacial, neuronal or pigmentation defects triggered by p53 hyperactivation in NCCs. Immunostaining analyses for two key apoptosis markers confirm that deleting Puma or Caspase9 does indeed impair p53-hyperactivation-induced apoptosis in NCCs. Furthermore, we demonstrate that p53 hyperactivation does not trigger a compensatory dampening of cell cycle progression in NCCs upon inactivation of apoptotic pathways. Together, our results indicate that p53-driven craniofacial, neuronal and pigmentation defects can arise in the absence of apoptosis and cell cycle arrest, suggesting that p53 hyperactivation can act via alternative pathways to trigger developmental phenotypes.

  View details for DOI 10.1038/s41418-021-00738-7

  View details for PubMedID 33574585

• Specifications of the ACMG/AMP variant interpretation guidelines for germline TP53 variants. Human mutation Fortuno, C., Lee, K., Olivier, M., Pesaran, T., Mai, P. L., de Andrade, K. C., Attardi, L. D., Crowley, S., Gareth Evans, D., Feng, B., Foreman, A. K., Frone, M. N., Huether, R., James, P. A., McGoldrick, K., Mester, J., Seifert, B. A., Slavin, T. P., Witkowski, L., Zhang, L., Plon, S. E., Spurdle, A. B., Savage, S. A., ClinGen TP53 Variant Curation Expert Panel 2020

  Abstract

  Germline pathogenic variants in TP53 are associated with Li-Fraumeni syndrome (LFS), a cancer predisposition disorder inherited in an autosomal dominant pattern associated with high risk of malignancy, including early onset breast cancers, sarcomas, adrenocortical carcinomas, and brain tumors. Intense cancer surveillance for individuals with TP53 germline pathogenic variants is associated with reduced cancer-related mortality. Accurate and consistent classification of germline variants across clinical and research laboratories is important to ensure appropriate cancer surveillance recommendations. Here, we describe the work performed by the Clinical Genome Resource TP53 Variant Curation Expert Panel (ClinGen TP53 VCEP) focused on specifying the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG/AMP) guidelines for germline variant classification to the TP53 gene. Specifications were developed for twenty ACMG/AMP criteria while nine were deemed not applicable. The original strength level for ten criteria was also adjusted due to current evidence. Use of TP53-specific guidelines and sharing of clinical data amongst experts and clinical laboratories led to a decrease in variants of uncertain significance from 28% to 12% compared with the original guidelines. The ClinGen TP53 VCEP recommends the use of these TP53-specific ACMG/AMP guidelines as the standard strategy for TP53 germline variant classification. This article is protected by copyright. All rights reserved.

  View details for DOI 10.1002/humu.24152

  View details for PubMedID 33300245

• Zmat3 Is a Key Splicing Regulator in the p53 Tumor Suppression Program. Molecular cell Bieging-Rolett, K. T., Kaiser, A. M., Morgens, D. W., Boutelle, A. M., Seoane, J. A., Van Nostrand, E. L., Zhu, C., Houlihan, S. L., Mello, S. S., Yee, B. A., McClendon, J., Pierce, S. E., Winters, I. P., Wang, M., Connolly, A. J., Lowe, S. W., Curtis, C., Yeo, G. W., Winslow, M. M., Bassik, M. C., Attardi, L. D. 2020; 80 (3): 452

  Abstract

  Although TP53 is the most commonly mutated gene in human cancers, the p53-dependent transcriptional programs mediating tumor suppression remain incompletely understood. Here, to uncover critical components downstream of p53 in tumor suppression, we perform unbiased RNAi and CRISPR-Cas9-based genetic screens invivo. These screens converge upon the p53-inducible gene Zmat3, encoding an RNA-binding protein, and we demonstrate that ZMAT3 is an important tumor suppressor downstream of p53 in mouse KrasG12D-driven lung and liver cancers and human carcinomas. Integrative analysis of the ZMAT3 RNA-binding landscape and transcriptomic profiling reveals that ZMAT3 directly modulates exon inclusion in transcripts encoding proteins of diverse functions, including the p53 inhibitors MDM4 and MDM2, splicing regulators, and components of varied cellular processes. Interestingly, these exons are enriched in NMD signals, and, accordingly, ZMAT3 broadly affects target transcript stability. Collectively, these studies reveal ZMAT3 as a novel RNA-splicing and homeostasis regulator and a key component of p53-mediated tumor suppression.

  View details for DOI 10.1016/j.molcel.2020.10.022

  View details for PubMedID 33157015

• Pilot study of loss of the p53/p63 target genePERPat the surgical margin as a potential predictor of local relapse in head and neck squamous cell carcinoma HEAD AND NECK-JOURNAL FOR THE SCIENCES AND SPECIALTIES OF THE HEAD AND NECK Holmes, B. J., von Eyben, R., Attardi, L. D., Kong, C. S., Le, Q., Nathan, C. O. 2020

  View details for DOI 10.1002/hed.26358

  View details for Web of Science ID 000545616600001

• Pilot study of loss of the p53/p63 target gene PERP at the surgical margin as a potential predictor of local relapse in head and neck squamous cell carcinoma. Head & neck Holmes, B. J., von Eyben, R., Attardi, L. D., Kong, C. S., Le, Q. T., Nathan, C. O. 2020

  Abstract

  PERP (p53 apoptosis effector related to PMP22) localizes to desmosomes and suppresses squamous cell carcinoma development. Loss of PERP leads to worse local control in head and neck squamous cell carcinoma (HNSCC), likely by destabilizing desmosomes. We evaluated PERP loss at HNSCC surgical margins as a predictor of local relapse.Combining discovery (n = 17) and validation (n = 31) cohorts, we examined membranous PERP protein expression by immunohistochemistry in surgical mucosal margins with competing risk analysis of the relationship between local relapse and PERP expression.Of the 44 analyzable patients, the 2-year cumulative incidence of local relapse was 44.4% for the PERP-negative group and 16.4% for the PERP-positive group (P = .01). A trend toward worse progression-free survival (P = .09) and overall survival (P = .06) was observed with loss of PERP.PERP loss at surgical margins is associated with higher risk of local recurrence in HNSCC, warranting further evaluation in a larger prospective study.

  View details for DOI 10.1002/hed.26358

  View details for PubMedID 33034918

• Deconstructing the origins of PDAC development. Flowers, B., Xu, H., Hanson, K., Curtis, C., Vogel, H., Wood, L., Attardi., L. D. AMER ASSOC CANCER RESEARCH. 2020: 19

  View details for Web of Science ID 000537844900012

• p53 deficiency triggers dysregulation of diverse cellular processes in physiological oxygen. The Journal of cell biology Valente, L. J., Tarangelo, A. n., Li, A. M., Naciri, M. n., Raj, N. n., Boutelle, A. M., Li, Y. n., Mello, S. S., Bieging-Rolett, K. n., DeBerardinis, R. J., Ye, J. n., Dixon, S. J., Attardi, L. D. 2020; 219 (11)

  Abstract

  The mechanisms by which TP53, the most frequently mutated gene in human cancer, suppresses tumorigenesis remain unclear. p53 modulates various cellular processes, such as apoptosis and proliferation, which has led to distinct cellular mechanisms being proposed for p53-mediated tumor suppression in different contexts. Here, we asked whether during tumor suppression p53 might instead regulate a wide range of cellular processes. Analysis of mouse and human oncogene-expressing wild-type and p53-deficient cells in physiological oxygen conditions revealed that p53 loss concurrently impacts numerous distinct cellular processes, including apoptosis, genome stabilization, DNA repair, metabolism, migration, and invasion. Notably, some phenotypes were uncovered only in physiological oxygen. Transcriptomic analysis in this setting highlighted underappreciated functions modulated by p53, including actin dynamics. Collectively, these results suggest that p53 simultaneously governs diverse cellular processes during transformation suppression, an aspect of p53 function that would provide a clear rationale for its frequent inactivation in human cancer.

  View details for DOI 10.1083/jcb.201908212

  View details for PubMedID 32886745

• Deciphering the origins of PDAC development Flowers, B., Xu, H., Hanson, K., Curtis, C., Vogel, H., Wood, L. D., Attardi, L. D. AMER ASSOC CANCER RESEARCH. 2019

  View details for DOI 10.1158/1538-7445.PANCA19-I15

  View details for Web of Science ID 000526416300153

• Elucidating the role of p53 in the cellular origins of pancreatic cancer development Flowers, B. M., Xu, H., Hanson, K., Curtis, C., Vogel, H., Wood, L. D., Attardi, L. D. AMER ASSOC CANCER RESEARCH. 2019

  View details for DOI 10.1158/1538-7445.PANCA19-A15

  View details for Web of Science ID 000526416300013

• The Spatiotemporal Pattern and Intensity of p53 Activation Dictates Phenotypic Diversity in p53-Driven Developmental Syndromes. Developmental cell Bowen, M. E., McClendon, J., Long, H. K., Sorayya, A., Van Nostrand, J. L., Wysocka, J., Attardi, L. D. 2019

  Abstract

  Inappropriate activation of the p53 transcription factor contributes to numerous developmental syndromes characterized by distinct constellations of phenotypes. How p53 drives exquisitely specific sets of symptoms in diverse syndromes, however, remains enigmatic. Here, we deconvolute the basis of p53-driven developmental syndromes by leveraging an array of mouse strains to modulate the spatial expression pattern, temporal profile, and magnitude of p53 activation during embryogenesis. We demonstrate that inappropriate p53 activation in the neural crest, facial ectoderm, anterior heart field, and endothelium induces distinct spectra of phenotypes. Moreover, altering the timing and degree of p53 hyperactivation substantially affects the phenotypic outcomes. Phenotypes are associated with p53-driven cell-cycle arrest or apoptosis, depending on the cell type, with gene expression programs, rather than extent of mitochondrial priming, largely governing the specific response. Together, our findings provide a critical framework for decoding the role of p53 as a mediator of diverse developmental syndromes.

  View details for DOI 10.1016/j.devcel.2019.05.015

  View details for PubMedID 31178404

• Genome Edited Human Hematopoietic Stem Cells Correct Lysosomal Storage Disorders: Proof-of-Concept and Safety Studies for Mucopolysaccharidosis Type I and Gaucher Disease Gomez-Ospina, N., Scharenberg, S., Mostrel, N., Raj, N., Attardi, L., Khan, S., Tomatsu, S., Lee, C., Bao, G., Porteus, M. H. CELL PRESS. 2019: 329

  View details for Web of Science ID 000464381003155

• The role of p53 in developmental syndromes JOURNAL OF MOLECULAR CELL BIOLOGY Bowen, M. E., Attardi, L. D. 2019; 11 (3): 200–211

  View details for DOI 10.1093/jmcb/mjy087

  View details for Web of Science ID 000467903600003

• The role of p53 in developmental syndromes. Journal of molecular cell biology Bowen, M. E., Attardi, L. D. 2019

  Abstract

  While it is well appreciated that loss of the p53 tumor suppressor protein promotes cancer, growing evidence indicates that increased p53 activity underlies the developmental defects in a wide range of genetic syndromes. The inherited or de novo mutations that cause these syndromes affect diverse cellular processes, such as ribosome biogenesis, DNA repair, and centriole duplication, and analysis of human patient samples and mouse models demonstrates that disrupting these cellular processes can activate the p53 pathway. Importantly, many of the developmental defects in mouse models of these syndromes can be rescued by loss of p53, indicating that inappropriate p53 activation directly contributes to their pathogenesis. A role for p53 in driving developmental defects is further supported by the observation that mouse strains with broad p53 hyperactivation, due to mutations affecting p53 pathway components, display a host of tissue-specific developmental defects, including hematopoietic, neuronal, craniofacial, cardiovascular, and pigmentation defects. Furthermore, germline activating mutations in TP53 were recently identified in two human patients exhibiting bone marrow failure and other developmental defects. Studies in mice suggest that p53 drives developmental defects by inducing apoptosis, restraining proliferation, or modulating other developmental programs in a cell type-dependent manner. Here, we review the growing body of evidence from mouse models that implicate p53 as a driver of tissue-specific developmental defects in diverse genetic syndromes.

  View details for PubMedID 30624728

• Human genome-edited hematopoietic stem cells phenotypically correct Mucopolysaccharidosis type I. Nature communications Gomez-Ospina, N. n., Scharenberg, S. G., Mostrel, N. n., Bak, R. O., Mantri, S. n., Quadros, R. M., Gurumurthy, C. B., Lee, C. n., Bao, G. n., Suarez, C. J., Khan, S. n., Sawamoto, K. n., Tomatsu, S. n., Raj, N. n., Attardi, L. D., Aurelian, L. n., Porteus, M. H. 2019; 10 (1): 4045

  Abstract

  Lysosomal enzyme deficiencies comprise a large group of genetic disorders that generally lack effective treatments. A potential treatment approach is to engineer the patient's own hematopoietic system to express high levels of the deficient enzyme, thereby correcting the biochemical defect and halting disease progression. Here, we present an efficient ex vivo genome editing approach using CRISPR-Cas9 that targets the lysosomal enzyme iduronidase to the CCR5 safe harbor locus in human CD34+ hematopoietic stem and progenitor cells. The modified cells secrete supra-endogenous enzyme levels, maintain long-term repopulation and multi-lineage differentiation potential, and can improve biochemical and phenotypic abnormalities in an immunocompromised mouse model of Mucopolysaccharidosis type I. These studies provide support for the development of genome-edited CD34+ hematopoietic stem and progenitor cells as a potential treatment for Mucopolysaccharidosis type I. The safe harbor approach constitutes a flexible platform for the expression of lysosomal enzymes making it applicable to other lysosomal storage disorders.

  View details for DOI 10.1038/s41467-019-11962-8

  View details for PubMedID 31492863

• SIDT2 RNA Transporter Promotes Lung and Gastrointestinal Tumor Development. iScience Nguyen, T. A., Bieging-Rolett, K. T., Putoczki, T. L., Wicks, I. P., Attardi, L. D., Pang, K. C. 2019; 20: 14–24

  Abstract

  RNautophagy is a newly described type of selective autophagy whereby cellular RNAs are transported into lysosomes for degradation. This process involves the transmembrane protein SIDT2, which transports double-stranded RNA (dsRNA) across the endolysosomal membrane. We previously demonstrated that SIDT2 is a transcriptional target of p53, but its role in tumorigenesis, if any, is unclear. Unexpectedly, we show here that Sidt2-/- mice with concurrent oncogenic KrasG12D activation develop significantly fewer tumors than littermate controls in a mouse model of lung adenocarcinoma. Consistent with this observation, loss of SIDT2 also leads to enhanced survival and delayed tumor development in an Apcmin/+ mouse model of intestinal cancer. Within the intestine, Apcmin/+;Sidt2-/- mice display accumulation of dsRNA in association with increased phosphorylation of eIF2α and JNK as well as elevated rates of apoptosis. Taken together, our data demonstrate a role for SIDT2, and by extension RNautophagy, in promoting tumor development.

  View details for DOI 10.1016/j.isci.2019.09.009

  View details for PubMedID 31546103

• Siva plays a critical role in mouse embryonic development. Cell death and differentiation Jacobs, S. B., Van Nostrand, J. L., Bowen, M. E., Baker, J. C., Attardi, L. D. 2019

  Abstract

  The Siva protein, named after the Hindu God of Destruction, plays important roles in apoptosis in various contexts, including downstream of death receptor activation or p53 tumor suppressor engagement. The function of Siva in organismal development and homeostasis, however, has remained uncharacterized. Here, we generate Siva knockout mice to characterize the physiological function of Siva in vivo. Interestingly, we find that Siva deficiency causes early embryonic lethality accompanied by multiple phenotypes, including developmental delay, abnormal neural tube closure, and defective placenta and yolk sac formation. Examination of Siva expression during embryogenesis shows that Siva is expressed in both embryonic and extra-embryonic tissues, including within the mesoderm, which may explain the vascular defects observed in the placenta and yolk sac. The embryonic phenotypes caused by Siva loss are not rescued by p53 deficiency, nor do they resemble those of p53 null embryos, suggesting that the embryonic function of Siva is not related to the p53 pathway. Moreover, loss of the Ripk3 necroptosis protein does not rescue the observed lethality or developmental defects, suggesting that Siva may play a non-apoptotic role in development. Collectively, these studies reveal a key role for Siva in proper embryonic development.

  View details for DOI 10.1038/s41418-019-0358-x

  View details for PubMedID 31164717

• Single Cell Transcriptomics Reveal Abnormalities in Neurosensory Patterning of the Chd7 Mutant Mouse Ear. Frontiers in genetics Durruthy-Durruthy, R., Sperry, E. D., Bowen, M. E., Attardi, L. D., Heller, S., Martin, D. M. 2018; 9: 473

  Abstract

  The chromatin remodeling protein CHD7 is critical for proper formation of the mammalian inner ear. Humans with heterozygous pathogenic variants in CHD7 exhibit CHARGE syndrome, characterized by hearing loss and inner ear dysplasia, including abnormalities of the semicircular canals and Mondini malformations. Chd7Gt/+ heterozygous null mutant mice also exhibit dysplastic semicircular canals and hearing loss. Prior studies have demonstrated that reduced Chd7 dosage in the ear disrupts expression of genes involved in morphogenesis and neurogenesis, yet the relationships between these changes in gene expression and otic patterning are not well understood. Here, we sought to define roles for CHD7 in global regulation of gene expression and patterning in the developing mouse ear. Using single-cell multiplex qRT-PCR, we analyzed expression of 192 genes in FAC sorted cells from Pax2Cre;mT/mGFP wild type and Chd7Gt/+ mutant microdissected mouse otocysts. We found that Chd7 haploinsufficient otocysts exhibit a relative enrichment of cells adopting a neuroblast (vs. otic) transcriptional identity compared with wild type. Additionally, we uncovered disruptions in pro-sensory and pro-neurogenic gene expression with Chd7 loss, including genes encoding proteins that function in Notch signaling. Our results suggest that Chd7 is required for early cell fate decisions in the developing ear that involve highly specific aspects of otic patterning and differentiation.

  View details for DOI 10.3389/fgene.2018.00473

  View details for PubMedID 30459807

  View details for PubMedCentralID PMC6232929

• Single Cell Transcriptomics Revea Abnormalities in Neurosensory Patterning of the Chd7 Mutant Mouse Ear FRONTIERS IN GENETICS Durruthy-Durruthy, R., Sperry, E. D., Bowen, M. E., Attardi, L. D., Heller, S., Martin, D. M. 2018; 9

  View details for DOI 10.3389/fgene.2018.00473

  View details for Web of Science ID 000448015400001

• Mutations in PERP Cause Dominant and Recessive Keratoderma. The Journal of investigative dermatology Duchatelet, S., Boyden, L. M., Ishida-Yamamoto, A., Zhou, J., Guibbal, L., Hu, R., Lim, Y. H., Bole-Feysot, C., Nitschke, P., Santos-Simarro, F., de Lucas, R., Milstone, L. M., Gildenstern, V., Helfrich, Y. R., Attardi, L. D., Lifton, R. P., Choate, K. A., Hovnanian, A. 2018

  Abstract

  Investigation of genetic determinants of Mendelian skin disorders has substantially advanced understanding of epidermal biology. Here we show that mutations in PERP, encoding a crucial component of desmosomes, cause both dominant and recessive human keratoderma. Heterozygosity for a C-terminal truncation, which produces a protein that appears to be unstably incorporated into desmosomes, causes Olmsted syndrome with severe periorificial and palmoplantar keratoderma in multiple unrelated kindreds. Homozygosity for an N-terminal truncation ablates expression and causes widespread erythrokeratoderma, with expansion of epidermal differentiation markers. Both exhibit epidermal hyperproliferation, immature desmosomes lacking a dense midline observed via electron microscopy, and impaired intercellular adhesion upon mechanical stress. Localization of other desmosomal components appears normal, which is in contrast to other conditions caused by mutations in genes encoding desmosomal proteins. These discoveries highlight the essential role of PERP in human desmosomes and epidermal homeostasis and further expand the heterogeneous spectrum of inherited keratinization disorders.

  View details for PubMedID 30321533

• Neat-en-ing up our understanding of p53 pathways in tumor suppression. Cell cycle (Georgetown, Tex.) Mello, S. S., Attardi, L. D. 2018

  Abstract

  Although the p53 transcription factor has a well-established role in tumor suppression, little is known about how the non-coding targets of p53 mediate its tumor suppression function. Analysis of ncRNAs regulated by p53 revealed Neat1 as a direct p53 target gene. Neat1 has physiological roles in the development and differentiation of the mammary gland and corpus luteum, but its roles in cancer have been conflicting. To unequivocally understand Neat1 function in cancer, we used Neat1 null mice. Interestingly, we found that Neat1 deficiency promotes transformation both in oncogene-expressing fibroblasts and in a mouse model for pancreatic cancer. Specifically, Neat1 loss in the pancreas results in the enhanced development of preneoplastic lesions associated with dampened expression of differentiation genes. While the exact mechanisms underlying tumor suppression are unknown, there are several described mechanisms that may be responsible for Neat1-mediated tumor suppression. Collectively, these findings suggest that Neat1 enforces differentiation to suppress pancreatic cancer.

  View details for PubMedID 29895201

• Understanding the role of the tumor suppressor p53 in pancreatic cancer development. Flowers, B. M., Garcia, P. B., Gruner, B. M., Winslow, M. M., Attardi, L. D. AMER ASSOC CANCER RESEARCH. 2018: 44–45

  View details for Web of Science ID 000432307300057

• Deconstructing p53 pathways in tumor suppression. Mello, S., Bieging-Rolett, K., Kaiser, A., Valente, E., Raj, N., McClendon, J., Flowers, B., Morgens, D., Bassik, M., Attardi, L. AMER ASSOC CANCER RESEARCH. 2018: 17

  View details for Web of Science ID 000432307300006

• Deciphering p53 signaling in tumor suppression CURRENT OPINION IN CELL BIOLOGY Mello, S. S., Attardi, L. D. 2018; 51: 65–72

  Abstract

  The p53 transcription factor is mutated in over half of human cancers, and p53-null mice are highly predisposed to cancer, highlighting p53s essential role in tumor suppression. Studies in mouse models have revealed that p53 cell cycle arrest and apoptosis responses to acute DNA damage signals are dispensable for tumor suppression, prompting a search for new mechanisms underlying p53-mediated cancer suppression. p53 responds to other types of stress signals and regulates a host other cellular processes, including maintenance of genomic stability, metabolism, stemness, non-apoptotic cell death, migration/invasion, and cell signaling, any or all of which could be fundamental for suppressing carcinogenesis. The ability of p53 to govern numerous transcriptional programs and cellular functions likely explains its potent tumor suppressor activity.

  View details for PubMedID 29195118

  View details for PubMedCentralID PMC5949255

• Tissue-selective effects of nucleolar stress and rDNA damage in developmental disorders NATURE Calo, E., Gu, B., Bowen, M. E., Aryan, F., Zalc, A., Liang, J., Flynn, R. A., Swigut, T., Chang, H. Y., Attardi, L. D., Wysocka, J. 2018; 554 (7690): 112-+

  Abstract

  Many craniofacial disorders are caused by heterozygous mutations in general regulators of housekeeping cellular functions such as transcription or ribosome biogenesis. Although it is understood that many of these malformations are a consequence of defects in cranial neural crest cells, a cell type that gives rise to most of the facial structures during embryogenesis, the mechanism underlying cell-type selectivity of these defects remains largely unknown. By exploring molecular functions of DDX21, a DEAD-box RNA helicase involved in control of both RNA polymerase (Pol) I- and II-dependent transcriptional arms of ribosome biogenesis, we uncovered a previously unappreciated mechanism linking nucleolar dysfunction, ribosomal DNA (rDNA) damage, and craniofacial malformations. Here we demonstrate that genetic perturbations associated with Treacher Collins syndrome, a craniofacial disorder caused by heterozygous mutations in components of the Pol I transcriptional machinery or its cofactor TCOF1 (ref. 1), lead to relocalization of DDX21 from the nucleolus to the nucleoplasm, its loss from the chromatin targets, as well as inhibition of rRNA processing and downregulation of ribosomal protein gene transcription. These effects are cell-type-selective, cell-autonomous, and involve activation of p53 tumour-suppressor protein. We further show that cranial neural crest cells are sensitized to p53-mediated apoptosis, but blocking DDX21 loss from the nucleolus and chromatin rescues both the susceptibility to apoptosis and the craniofacial phenotypes associated with Treacher Collins syndrome. This mechanism is not restricted to cranial neural crest cells, as blood formation is also hypersensitive to loss of DDX21 functions. Accordingly, ribosomal gene perturbations associated with Diamond-Blackfan anaemia disrupt DDX21 localization. At the molecular level, we demonstrate that impaired rRNA synthesis elicits a DNA damage response, and that rDNA damage results in tissue-selective and dosage-dependent effects on craniofacial development. Taken together, our findings illustrate how disruption in general regulators that compromise nucleolar homeostasis can result in tissue-selective malformations.

  View details for PubMedID 29364875

• p53 Suppresses Metabolic Stress-Induced Ferroptosis in Cancer Cells CELL REPORTS Tarangelo, A., Magtanong, L., Bieging-Rolett, K. T., Li, Y., Ye, J., Attardi, L. D., Dixon, S. J. 2018; 22 (3): 569–75

  Abstract

  How cancer cells respond to nutrient deprivation remains poorly understood. In certain cancer cells, deprivation of cystine induces a non-apoptotic, iron-dependent form of cell death termed ferroptosis. Recent evidence suggests that ferroptosis sensitivity may be modulated by the stress-responsive transcription factor and canonical tumor suppressor protein p53. Using CRISPR/Cas9 genome editing, small-molecule probes, and high-resolution, time-lapse imaging, we find that stabilization of wild-type p53 delays the onset of ferroptosis in response to cystine deprivation. This delay requires the p53 transcriptional target CDKN1A (encoding p21) and is associated with both slower depletion of intracellular glutathione and a reduced accumulation of toxic lipid-reactive oxygen species (ROS). Thus, the p53-p21 axis may help cancer cells cope with metabolic stress induced by cystine deprivation by delaying the onset of non-apoptotic cell death.

  View details for PubMedID 29346757

• Deconstructing networks of p53-mediated tumor suppression in vivo CELL DEATH AND DIFFERENTIATION Kaiser, A. M., Attardi, L. D. 2018; 25 (1): 93–103

  Abstract

  The transcription factor p53 is a vital tumor suppressor. Upon activation by diverse stresses including oncogene activation, DNA damage, hypoxia and nutrient deprivation, p53 activates a panoply of target genes and orchestrates numerous downstream responses that suppress tumorigenesis. Although early studies of p53 suggested that its ability to induce cell cycle arrest, senescence and apoptosis programs accounted for its tumor-suppressor activity, more recent studies have challenged this notion. Moreover, p53 regulates a suite of additional processes, such as metabolism, stem cell function, invasion and metastasis. The processes p53 coordinately regulates to enact tumor suppression, and how such regulation occurs, thus remain elusive. In this review, we will summarize our current knowledge of p53-mediated tumor-suppressive mechanisms gleaned from in vivo studies in mouse models.

  View details for PubMedID 29099489

  View details for PubMedCentralID PMC5729531

• Deconstructing networks of p53-mediated tumor suppression in vivo. Cell death and differentiation Kaiser, A. M., Attardi, L. D. 2018; 25 (1): 93–103

  Abstract

  The transcription factor p53 is a vital tumor suppressor. Upon activation by diverse stresses including oncogene activation, DNA damage, hypoxia and nutrient deprivation, p53 activates a panoply of target genes and orchestrates numerous downstream responses that suppress tumorigenesis. Although early studies of p53 suggested that its ability to induce cell cycle arrest, senescence and apoptosis programs accounted for its tumor-suppressor activity, more recent studies have challenged this notion. Moreover, p53 regulates a suite of additional processes, such as metabolism, stem cell function, invasion and metastasis. The processes p53 coordinately regulates to enact tumor suppression, and how such regulation occurs, thus remain elusive. In this review, we will summarize our current knowledge of p53-mediated tumor-suppressive mechanisms gleaned from in vivo studies in mouse models.

  View details for DOI 10.1038/cdd.2017.171

  View details for PubMedID 31745313

• Loss of PERP p53/p63 target gene may indicate tumorigenesis at the margin and local recurrence Simmons, A., Kong, C., von Eyben, R., Attardi, L., Ma, X., Quynh-Thu Le, Nathan, C. AMER ASSOC CANCER RESEARCH. 2017

  View details for Web of Science ID 000416946500071

• Essential role for centromeric factors following p53 loss and oncogenic transformation GENES & DEVELOPMENT Filipescu, D., Naughtin, M., Podsypanina, K., Lejour, V., Wilson, L., Gurard-Levin, Z. A., Orsi, G. A., Simeonova, I., Toufektchan, E., Attardi, L. D., Toledo, F., Almouzni, G. 2017; 31 (5): 463-480

  Abstract

  In mammals, centromere definition involves the histone variant CENP-A (centromere protein A), deposited by its chaperone, HJURP (Holliday junction recognition protein). Alterations in this process impair chromosome segregation and genome stability, which are also compromised by p53 inactivation in cancer. Here we found that CENP-A and HJURP are transcriptionally up-regulated in p53-null human tumors. Using an established mouse embryonic fibroblast (MEF) model combining p53 inactivation with E1A or HRas-V12 oncogene expression, we reproduced a similar up-regulation of HJURP and CENP-A. We delineate functional CDE/CHR motifs within the Hjurp and Cenpa promoters and demonstrate their roles in p53-mediated repression. To assess the importance of HJURP up-regulation in transformed murine and human cells, we used a CRISPR/Cas9 approach. Remarkably, depletion of HJURP leads to distinct outcomes depending on their p53 status. Functional p53 elicits a cell cycle arrest response, whereas, in p53-null transformed cells, the absence of arrest enables the loss of HJURP to induce severe aneuploidy and, ultimately, apoptotic cell death. We thus tested the impact of HJURP depletion in pre-established allograft tumors in mice and revealed a major block of tumor progression in vivo. We discuss a model in which an "epigenetic addiction" to the HJURP chaperone represents an Achilles' heel in p53-deficient transformed cells.

  View details for DOI 10.1101/gad.290924.116

  View details for Web of Science ID 000398389400003

  View details for PubMedID 28356341

• The p53 family members have distinct roles during mammalian embryonic development. Cell death and differentiation Van Nostrand, J. L., Bowen, M. E., Vogel, H., Barna, M., Attardi, L. D. 2017

  Abstract

  The p53 tumor suppressor is a member of a multi-protein family, including the p63 and p73 transcription factors. These proteins can bind to the same consensus sites in DNA and activate the same target genes, suggesting that there could be functional redundancy between them. Indeed, double mutant mice heterozygous for any two family member-encoding genes display enhanced cancer phenotypes relative to single heterozygous mutants. However, whether the family members play redundant roles during embryonic development has remained largely unexplored. Although p53(-/-); p73(-/-) mice are born and manifest phenotypes characteristic of each of the single mutants, the consequences of combined deficiency of p63 and either p53 or p73 have not been elucidated. To examine the functional overlap of p53 family members during development, we bred and analyzed compound mutant embryo phenotypes. We discovered that double knockout embryos and five allele knockout embryos only displayed obvious defects accounted for by loss of single p53 family members. Surprisingly, at mid-gestation (E11), we identified a single viable triple knockout embryo that appeared grossly normal. Together, these results suggest that the p53 family is not absolutely required for early embryogenesis and that p53 family members are largely non-redundant during early development.

  View details for DOI 10.1038/cdd.2016.128

  View details for PubMedID 28211873

• The Transactivation Domains of the p53 Protein. Cold Spring Harbor perspectives in medicine Raj, N., Attardi, L. D. 2017; 7 (1)

  Abstract

  The p53 tumor suppressor is a transcriptional activator, with discrete domains that participate in sequence-specific DNA binding, tetramerization, and transcriptional activation. Mutagenesis and reporter studies have delineated two distinct activation domains (TADs) and specific hydrophobic residues within these TADs that are critical for their function. Knockin mice expressing p53 mutants with alterations in either or both of the two TADs have revealed that TAD1 is critical for responses to acute DNA damage, whereas both TAD1 and TAD2 participate in tumor suppression. Biochemical and structural studies have identified factors that bind either or both TADs, including general transcription factors (GTFs), chromatin modifiers, and negative regulators, helping to elaborate a model through which p53 activates transcription. Posttranslational modifications (PTMs) of the p53 TADs through phosphorylation also regulate TAD activity. Together, these studies on p53 TADs provide great insight into how p53 serves as a tumor suppressor.

  View details for DOI 10.1101/cshperspect.a026047

  View details for PubMedID 27864306

• Neat1 is a p53-inducible lincRNA essential for transformation suppression. Genes & development Mello, S. S., Sinow, C. n., Raj, N. n., Mazur, P. K., Bieging-Rolett, K. n., Broz, D. K., Imam, J. F., Vogel, H. n., Wood, L. D., Sage, J. n., Hirose, T. n., Nakagawa, S. n., Rinn, J. n., Attardi, L. D. 2017; 31 (11): 1095–1108

  Abstract

  The p53 gene is mutated in over half of all cancers, reflecting its critical role as a tumor suppressor. Although p53 is a transcriptional activator that induces myriad target genes, those p53-inducible genes most critical for tumor suppression remain elusive. Here, we leveraged p53 ChIP-seq (chromatin immunoprecipitation [ChIP] combined with high-throughput sequencing) and RNA-seq (RNA sequencing) data sets to identify new p53 target genes, focusing on the noncoding genome. We identify Neat1, a noncoding RNA (ncRNA) constituent of paraspeckles, as a p53 target gene broadly induced by mouse and human p53 in different cell types and by diverse stress signals. Using fibroblasts derived from Neat1(-/-) mice, we examined the functional role of Neat1 in the p53 pathway. We found that Neat1 is dispensable for cell cycle arrest and apoptosis in response to genotoxic stress. In sharp contrast, Neat1 plays a crucial role in suppressing transformation in response to oncogenic signals. Neat1 deficiency enhances transformation in oncogene-expressing fibroblasts and promotes the development of premalignant pancreatic intraepithelial neoplasias (PanINs) and cystic lesions in Kras(G12D)-expressing mice. Neat1 loss provokes global changes in gene expression, suggesting a mechanism by which its deficiency promotes neoplasia. Collectively, these findings identify Neat1 as a p53-regulated large intergenic ncRNA (lincRNA) with a key role in suppressing transformation and cancer initiation, providing fundamental new insight into p53-mediated tumor suppression.

  View details for PubMedID 28698299

• A p53 Super-tumor Suppressor Reveals a Tumor Suppressive p53-Ptpn14-Yap Axis in Pancreatic Cancer. Cancer cell Mello, S. S., Valente, L. J., Raj, N. n., Seoane, J. A., Flowers, B. M., McClendon, J. n., Bieging-Rolett, K. T., Lee, J. n., Ivanochko, D. n., Kozak, M. M., Chang, D. T., Longacre, T. A., Koong, A. C., Arrowsmith, C. H., Kim, S. K., Vogel, H. n., Wood, L. D., Hruban, R. H., Curtis, C. n., Attardi, L. D. 2017; 32 (4): 460–73.e6

  Abstract

  The p53 transcription factor is a critical barrier to pancreatic cancer progression. To unravel mechanisms of p53-mediated tumor suppression, which have remained elusive, we analyzed pancreatic cancer development in mice expressing p53 transcriptional activation domain (TAD) mutants. Surprisingly, the p5353,54 TAD2 mutant behaves as a "super-tumor suppressor," with an enhanced capacity to both suppress pancreatic cancer and transactivate select p53 target genes, including Ptpn14. Ptpn14 encodes a negative regulator of the Yap oncoprotein and is necessary and sufficient for pancreatic cancer suppression, like p53. We show that p53 deficiency promotes Yap signaling and that PTPN14 and TP53 mutations are mutually exclusive in human cancers. These studies uncover a p53-Ptpn14-Yap pathway that is integral to p53-mediated tumor suppression.

  View details for PubMedID 29017057

• ErbB2-dependent downregulation of a pro-apoptotic protein Perp is required for oncogenic transformation of breast epithelial cells. Oncogene Khan, I. A., Yoo, B. H., Masson, O., Baron, S., CORKERY, D., Dellaire, G., Attardi, L. D., ROSEN, K. V. 2016; 35 (44): 5759-5769

  Abstract

  The ability of breast cancer cells to resist anoikis, apoptosis caused by detachment of the non-malignant epithelial cells from the extracellular matrix (ECM), is thought to be critical for breast tumor growth, invasion and metastasis. ErbB2, an oncoprotein that is often overproduced in breast tumors, can block breast cancer cell anoikis via mechanisms that are understood only in part. In an effort to understand them better we found that detachment of the non-malignant human breast epithelial cells from the ECM upregulates a protein Perp in these cells. Perp is a component of the desmosomes, multiprotein complexes involved in cell-to-cell adhesion. Perp can cause apoptosis via unknown mechanisms. We demonstrated that Perp upregulation by cell detachment is driven by detachment-induced loss of epidermal growth factor receptor (EGFR). We also found that Perp knockdown by RNA interference (RNAi) rescues detached cells from death which indicates that Perp contributes to their anoikis. We observed that ErbB2, when overexpressed in detached breast epithelial cells, causes Perp downregulation. Furthermore, ErbB2-directed RNAi or treatment with lapatinib, an ErbB2/EGFR small-molecule inhibitor used for breast cancer therapy, upregulated Perp in ErbB2-positive human breast and ovarian carcinoma cells. We established that ErbB2 downregulates Perp by activating an ErbB2 effector protein kinase Mek that blocks detachment-induced EGFR loss in a manner that requires the presence of a signaling protein Sprouty-2. Finally, we observed that restoration of the wild-type Perp levels in ErbB2-overproducing breast epithelial cells increases their anoikis susceptibility and blocks their clonogenicity in the absence of adhesion to the ECM. In summary, we have identified a novel mechanism of ErbB2-mediated mechanism of anoikis resistance of ErbB2-overproducing breast epithelial cells. This mechanism allows such cells to grow without adhesion to the ECM and is driven by ErbB2-induced activation of Mek, subsequent EGFR upregulation and further EGFR-dependent Perp loss.

  View details for DOI 10.1038/onc.2016.109

  View details for PubMedID 27109096

• An inducible long noncoding RNA amplifies DNA damage signaling. Nature genetics Schmitt, A. M., Garcia, J. T., Hung, T., Flynn, R. A., Shen, Y., Qu, K., Payumo, A. Y., Peres-da-Silva, A., Broz, D. K., Baum, R., Guo, S., Chen, J. K., Attardi, L. D., Chang, H. Y. 2016; 48 (11): 1370-1376

  Abstract

  Long noncoding RNAs (lncRNAs) are prevalent genes with frequently precise regulation but mostly unknown functions. Here we demonstrate that lncRNAs guide the organismal DNA damage response. DNA damage activated transcription of the DINO (Damage Induced Noncoding) lncRNA via p53. DINO was required for p53-dependent gene expression, cell cycle arrest and apoptosis in response to DNA damage, and DINO expression was sufficient to activate damage signaling and cell cycle arrest in the absence of DNA damage. DINO bound to p53 protein and promoted its stabilization, mediating a p53 auto-amplification loop. Dino knockout or promoter inactivation in mice dampened p53 signaling and ameliorated acute radiation syndrome in vivo. Thus, inducible lncRNA can create a feedback loop with its cognate transcription factor to amplify cellular signaling networks.

  View details for DOI 10.1038/ng.3673

  View details for PubMedID 27668660

• p19(Arf) is required for the cellular response to chronic DNA damage. Oncogene Bieging-Rolett, K. T., Johnson, T. M., Brady, C. A., Beaudry, V. G., Pathak, N., Han, S., Attardi, L. D. 2016; 35 (33): 4414-4421

  Abstract

  The p53 tumor suppressor is a stress sensor, driving cell cycle arrest or apoptosis in response to DNA damage or oncogenic signals. p53 activation by oncogenic signals relies on the p19(Arf) tumor suppressor, while p53 activation downstream of acute DNA damage is reported to be p19(Arf)-independent. Accordingly, p19(Arf)-deficient mouse embryo fibroblasts (MEFs) arrest in response to acute DNA damage. However, p19(Arf) is required for replicative senescence, a condition associated with an activated DNA damage response, as p19(Arf)-/- MEFs do not senesce after serial passage. A possible explanation for these seemingly disparate roles for p19(Arf) is that acute and chronic DNA damage responses are mechanistically distinct. Replicative senescence may result from chronic, low-dose DNA damage responses in which p19(Arf) has a specific role. We therefore examined the role of p19(Arf) in cellular responses to chronic, low-dose DNA-damaging agent treatment by maintaining MEFs in low oxygen and administering 0.5 G y γ-irradiation daily or 150 μM hydroxyurea, a replication stress inducer. In contrast to their response to acute DNA damage, p19(Arf)-/- MEFs exposed to chronic DNA damage do not senesce, revealing a selective role for p19(Arf) in senescence upon low-level, chronic DNA damage. We show further that p53 pathway activation in p19(Arf)-/- MEFs exposed to chronic DNA damage is attenuated relative to wild-type MEFs, suggesting a role for p19(Arf) in fine-tuning p53 activity. However, combined Nutlin3a and chronic DNA-damaging agent treatment is insufficient to promote senescence in p19(Arf)-/- MEFs, suggesting that the role of p19(Arf) in the chronic DNA damage response may be partially p53-independent. These data suggest the importance of p19(Arf) for the cellular response to the low-level DNA damage incurred in culture or upon oncogene expression, providing new insight into how p19(Arf) serves as a tumor suppressor. Moreover, our study helps reconcile reports suggesting crucial roles for both p19(Arf) and DNA damage-signaling pathways in tumor suppression.

  View details for DOI 10.1038/onc.2015.490

  View details for PubMedID 26725325

  View details for PubMedCentralID PMC4931997

• p73 anc FoxJ1: Programming Multiciliated Epithelia TRENDS IN CELL BIOLOGY Jackson, P. K., Attardi, L. D. 2016; 26 (4): 239–40

  Abstract

  The mysteriously diverse phenotypes in mice lacking the p53 homolog p73 are recently unified by new analysis showing p73 is required for formation of multiciliated epithelia. p73 directly activates FoxJ1, the central transcriptional driver for multiciliation, and induces a host of genes critical for ciliogenesis.

  View details for PubMedID 26988441

• Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition) AUTOPHAGY Klionsky, D. J., Abdelmohsen, K., Abe, A., Abedin, M. J., Abeliovich, H., Arozena, A. A., Adachi, H., Adams, C. M., Adams, P. D., Adeli, K., Adhihetty, P. J., Adler, S. G., Agam, G., Agarwal, R., Aghi, M. K., Agnello, M., Agostinis, P., Aguilar, P. V., Aguirre-Ghiso, J., Airoldi, E. M., Ait-Si-Ali, S., Akematsu, T., Akporiaye, E. T., Al-Rubeai, M., Albaiceta, G. M., Albanese, C., Albani, D., Albert, M. L., Aldudo, J., Alguel, H., Alirezaei, M., Alloza, I., Almasan, A., Almonte-Beceril, M., Alnemri, E. S., Alonso, C., Altan-Bonnet, N., Altieri, D. C., Alvarez, S., Alvarez-Erviti, L., Alves, S., Amadoro, G., Amano, A., Amantini, C., Ambrosio, S., Amelio, I., Amer, A. O., Amessou, M., Amon, A., An, Z., Anania, F. A., Andersen, S. U., Andley, U. P., Andreadi, C. K., Andrieu-Abadie, N., Anel, A., Ann, D. 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W., Szatmari, Z., Szegezdi, E., Szlosarek, P. W., Taegtmeyer, H., Tafani, M., Taillebourg, E., Tait, S. W., Takacs-Vellai, K., Takahashi, Y., Takats, S., Takemura, G., Takigawa, N., Talbot, N. J., Tamagno, E., Tamburini, J., Tan, C., Tan, L., Tan, M. L., Tan, M., Tan, Y., Tanaka, K., Tanaka, M., Tang, D., Tang, D., Tang, G., Tanida, I., Tanji, K., Tannous, B. A., Tapia, J. A., Tasset-Cuevas, I., Tatar, M., Tavassoly, I., Tavernarakis, N., Taylor, A., Taylor, G. S., Taylor, G. A., Taylor, J. P., Taylor, M. J., Tchetina, E. V., Tee, A. R., Teixeira-Clerc, F., Telang, S., Tencomnao, T., Teng, B., Teng, R., Terro, F., Tettamanti, G., Theiss, A. L., Theron, A. E., Thomas, K. J., Thome, M. P., Thomes, P. G., Thorburn, A., Thorner, J., Thum, T., Thumm, M., Thurston, T. L., Tian, L., Till, A., Ting, J. P., Titorenko, V. I., Toker, L., Toldo, S., Tooze, S. A., Topisirovic, I., Torgersen, M. L., Torosantucci, L., Torriglia, A., Torrisi, M. R., Tournier, C., Towns, R., Trajkovic, V., Travassos, L. H., Triola, G., Tripathi, D. N., Trisciuoglio, D., Troncoso, R., Trougakos, I. P., Truttmann, A. C., Tsai, K., Tschan, M. P., Tseng, Y., Tsukuba, T., Tsung, A., Tsvetkov, A. S., Tu, S., Tuan, H., Tucci, M., Tumbarello, D. A., Turk, B., Turk, V., Turner, R. F., Tveita, A. A., Tyagi, S. C., Ubukata, M., Uchiyama, Y., Udelnow, A., Ueno, T., Umekawa, M., Umemiya-Shirafuji, R., Underwood, B. R., Ungermann, C., Ureshino, R. P., Ushioda, R., Uversky, V. N., Uzcategui, N. L., Vaccari, T., Vaccaro, M. I., Vachova, L., Vakifahmetoglu-Norberg, H., Valdor, R., Valente, E. M., Vallette, F., Valverde, A. M., Van den Berghe, G., Van Den Bosch, L., van den Brink, G. R., van der Goot, F. G., van der Klei, I. J., van der Laan, L. J., van Doorn, W. G., van Egmond, M., van Golen, K. L., Van Kaer, L., Campagne, M. v., Vandenabeele, P., Vandenberghe, W., Vanhorebeek, I., Varela-Nieto, I., Vasconcelos, M. H., Vasko, R., Vavvas, D. G., Vega-Naredo, I., Velasco, G., Velentzas, A. D., Velentzas, P. D., Vellai, T., Vellenga, E., Vendelbo, M. H., Venkatachalam, K., Ventura, N., Ventura, S., Veras, P. S., Verdier, M., Vertessy, B. G., Viale, A., Vidal, M., Vieira, H. L., Vierstra, R. D., Vigneswaran, N., Vij, N., Vila, M., Villar, M., Villar, V. H., Villarroya, J., Vindis, C., Viola, G., Viscomi, M. T., Vitale, G., Vogl, D. T., Voitsekhovskaja, O. V., von Haefen, C., von Schwarzenberg, K., Voth, D. E., Vouret-Craviari, V., Vuori, K., Vyas, J. M., Waeber, C., Walker, C. L., Walker, M. J., Walter, J., Wan, L., Wan, X., Wang, B., Wang, C., Wang, C., Wang, C., Wang, C., Wang, C., Wang, D., Wang, F., Wang, F., Wang, G., Wang, H., Wang, H., Wang, H., Wang, H., Wang, H., Wang, J., Wang, J., Wang, M., Wang, M., Wang, P., Wang, P., Wang, R. C., Wang, S., Wang, T., Wang, X., Wang, X., Wang, X., Wang, X., Wang, X., Wang, Y., Wang, Y., Wang, Y., Wang, Y., Wang, Y., Wang, Y., Wang, Y. T., Wang, Y., Wang, Z., Wappner, P., Ward, C., Ward, D. M., Warnes, G., Watada, H., Watanabe, Y., Watase, K., Weaver, T. E., Weekes, C. D., Wei, J., Weide, T., Weihl, C. C., Weindl, G., Weis, S. N., Wen, L., Wen, X., Wen, Y., Westermann, B., Weyand, C. M., White, A. R., White, E., Whitton, J. L., Whitworth, A. J., Wiels, J., Wild, F., Wildenberg, M. E., Wileman, T., Wilkinson, D. S., Wilkinson, S., Willbold, D., Williams, C., Williams, K., Williamson, P. R., Winklhofer, K. F., Witkin, S. S., Wohlgemuth, S. E., Wollert, T., Wolvetang, E. J., Wong, E., Wong, G. W., Wong, R. W., Wong, V. K., Woodcock, E. A., Wright, K. L., Wu, C., Wu, D., Wu, G. S., Wu, J., Wu, J., Wu, M., Wu, M., Wu, S., Wu, W. K., Wu, Y., Wu, Z., Xavier, C. P., Xavier, R. J., Xia, G., Xia, T., Xia, W., Xia, Y., Xiao, H., Xiao, J., Xiao, S., Xiao, W., Xie, C., Xie, Z., Xie, Z., Xilouri, M., Xiong, Y., Xu, C., Xu, C., Xu, F., Xu, H., Xu, H., Xu, J., Xu, J., Xu, J., Xu, L., Xu, X., Xu, Y., Xu, Y., Xu, Z., Xu, Z., Xue, Y., Yamada, T., Yamamoto, A., Yamanaka, K., Yamashina, S., Yamashiro, S., Yan, B., Yan, B., Yan, X., Yan, Z., Yanagi, Y., Yang, D., Yang, J., Yang, L., Yang, M., Yang, P., Yang, P., Yang, Q., Yang, W., Yang, W. Y., Yang, X., Yang, Y., Yang, Y., Yang, Z., Yang, Z., Yao, M., Yao, P. J., Yao, X., Yao, Z., Yao, Z., Yasui, L. S., Ye, M., Yedvobnick, B., Yeganeh, B., Yeh, E. S., Yeyati, P. L., Yi, F., Yi, L., Yin, X., Yip, C. K., Yoo, Y., Yoo, Y. H., Yoon, S., Yoshida, K., Yoshimori, T., Young, K. H., Yu, H., Yu, J. J., Yu, J., Yu, J., Yu, L., Yu, W. H., Yu, X., Yu, Z., Yuan, J., Yuan, Z., Yue, B. Y., Yue, J., Yue, Z., Zacks, D. N., Zacksenhaus, E., Zaffaroni, N., Zaglia, T., Zakeri, Z., Zecchini, V., Zeng, J., Zeng, M., Zeng, Q., Zervos, A. S., Zhang, D. D., Zhang, F., Zhang, G., Zhang, G., Zhang, H., Zhang, H., Zhang, H., Zhang, H., Zhang, J., Zhang, J., Zhang, J., Zhang, J., Zhang, J., Zhang, L., Zhang, L., Zhang, L., Zhang, L., Zhang, M., Zhang, X., Zhang, X. D., Zhang, Y., Zhang, Y., Zhang, Y., Zhang, Y., Zhang, Y., Zhao, M., Zhao, W., Zhao, X., Zhao, Y. G., Zhao, Y., Zhao, Y., Zhao, Y., Zhao, Z., Zhao, Z. J., Zheng, D., Zheng, X., Zheng, X., Zhivotovsky, B., Zhong, Q., Zhou, G., Zhou, G., Zhou, H., Zhou, S., Zhou, X., Zhu, H., Zhu, H., Zhu, W., Zhu, W., Zhu, X., Zhu, Y., Zhuang, S., Zhuang, X., Ziparo, E., Zois, C. E., Zoladek, T., Zong, W., Zorzano, A., Zughaier, S. M. 2016; 12 (1): 1-222

  View details for DOI 10.1080/15548627.2015.1100356

  View details for PubMedID 26799652

• Combined inhibition of BET family proteins and histone deacetylases as a potential epigenetics-based therapy for pancreatic ductal adenocarcinoma. Nature medicine Mazur, P. K., Herner, A., Mello, S. S., Wirth, M., Hausmann, S., Sánchez-Rivera, F. J., Lofgren, S. M., Kuschma, T., Hahn, S. A., Vangala, D., Trajkovic-Arsic, M., Gupta, A., Heid, I., Noël, P. B., Braren, R., Erkan, M., Kleeff, J., Sipos, B., Sayles, L. C., Heikenwalder, M., Heßmann, E., Ellenrieder, V., Esposito, I., Jacks, T., Bradner, J. E., Khatri, P., Sweet-Cordero, E. A., Attardi, L. D., Schmid, R. M., Schneider, G., Sage, J., Siveke, J. T. 2015; 21 (10): 1163-1171

  Abstract

  Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human cancers and shows resistance to any therapeutic strategy used. Here we tested small-molecule inhibitors targeting chromatin regulators as possible therapeutic agents in PDAC. We show that JQ1, an inhibitor of the bromodomain and extraterminal (BET) family of proteins, suppresses PDAC development in mice by inhibiting both MYC activity and inflammatory signals. The histone deacetylase (HDAC) inhibitor SAHA synergizes with JQ1 to augment cell death and more potently suppress advanced PDAC. Finally, using a CRISPR-Cas9-based method for gene editing directly in the mouse adult pancreas, we show that de-repression of p57 (also known as KIP2 or CDKN1C) upon combined BET and HDAC inhibition is required for the induction of combination therapy-induced cell death in PDAC. SAHA is approved for human use, and molecules similar to JQ1 are being tested in clinical trials. Thus, these studies identify a promising epigenetic-based therapeutic strategy that may be rapidly implemented in fatal human tumors.

  View details for DOI 10.1038/nm.3952

  View details for PubMedID 26390243

• Combined inhibition of BET family proteins and histone deacetylases as a potential epigenetics-based therapy for pancreatic ductal adenocarcinoma NATURE MEDICINE Mazur, P. K., Herner, A., Mello, S. S., Wirth, M., Hausmann, S., Sanchez-Rivera, F. J., Lofgren, S. M., Kuschma, T., Hahn, S. A., Vangala, D., Trajkovic-Arsic, M., Gupta, A., Heid, I., Noel, P. B., Braren, R., Erkan, M., Kleeff, J., Sipos, B., Sayles, L. C., Heikenwalder, M., Hessmann, E., Ellenrieder, V., Esposito, I., Jacks, T., Bradner, J. E., Khatri, P., Sweet-Cordero, E. A., Attardi, L. D., Schmid, R. M., Schneider, G., Sage, J., Siveke, J. T. 2015; 21 (10): 1163-?

  Abstract

  Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal human cancers and shows resistance to any therapeutic strategy used. Here we tested small-molecule inhibitors targeting chromatin regulators as possible therapeutic agents in PDAC. We show that JQ1, an inhibitor of the bromodomain and extraterminal (BET) family of proteins, suppresses PDAC development in mice by inhibiting both MYC activity and inflammatory signals. The histone deacetylase (HDAC) inhibitor SAHA synergizes with JQ1 to augment cell death and more potently suppress advanced PDAC. Finally, using a CRISPR-Cas9-based method for gene editing directly in the mouse adult pancreas, we show that de-repression of p57 (also known as KIP2 or CDKN1C) upon combined BET and HDAC inhibition is required for the induction of combination therapy-induced cell death in PDAC. SAHA is approved for human use, and molecules similar to JQ1 are being tested in clinical trials. Thus, these studies identify a promising epigenetic-based therapeutic strategy that may be rapidly implemented in fatal human tumors.

  View details for DOI 10.1038/nm.3952

  View details for Web of Science ID 000362355400018

  View details for PubMedID 26390243

• The p53 Target Gene SIVA Enables Non-Small Cell Lung Cancer Development. Cancer discovery Van Nostrand, J. L., Brisac, A., Mello, S. S., Jacobs, S. B., Luong, R., Attardi, L. D. 2015; 5 (6): 622-635

  Abstract

  Although p53 transcriptional activation potential is critical for its ability to suppress cancer, the specific target genes involved in tumor suppression remain unclear. SIVA is a p53 target gene essential for p53-dependent apoptosis, although it can also promote proliferation through inhibition of p53 in some settings. Thus, the role of SIVA in tumorigenesis remains unclear. Here, we seek to define the contribution of SIVA to tumorigenesis by generating Siva conditional knockout mice. Surprisingly, we find that SIVA loss inhibits non-small cell lung cancer (NSCLC) development, suggesting that SIVA facilitates tumorigenesis. Similarly, SIVA knockdown in mouse and human NSCLC cell lines decreases proliferation and transformation. Consistent with this protumorigenic role for SIVA, high-level SIVA expression correlates with reduced NSCLC patient survival. SIVA acts independently of p53 and, instead, stimulates mTOR signaling and metabolism in NSCLC cells. Thus, SIVA enables tumorigenesis in a p53-independent manner, revealing a potential new cancer therapy target.These findings collectively reveal a novel role for the p53 target gene SIVA both in regulating metabolism and in enabling tumorigenesis, independently of p53. Importantly, these studies further identify SIVA as a new prognostic marker and as a potential target for NSCLC cancer therapy.

  View details for DOI 10.1158/2159-8290.CD-14-0921

  View details for PubMedID 25813352

  View details for PubMedCentralID PMC4456277

• Integrative genomic analysis reveals widespread enhancer regulation by p53 in response to DNA damage NUCLEIC ACIDS RESEARCH Younger, S. T., Kenzelmann-Broz, D., Jung, H., Attardi, L. D., Rinn, J. L. 2015; 43 (9): 4447-4462

  Abstract

  The tumor suppressor p53 has been studied extensively as a direct transcriptional activator of protein-coding genes. Recent studies, however, have shed light on novel regulatory functions of p53 within noncoding regions of the genome. Here, we use a systematic approach that integrates transcriptome-wide expression analysis, genome-wide p53 binding profiles and chromatin state maps to characterize the global regulatory roles of p53 in response to DNA damage. Notably, our approach identified conserved features of the p53 network in both human and mouse primary fibroblast models. In addition to known p53 targets, we identify many previously unappreciated mRNAs and long noncoding RNAs that are regulated by p53. Moreover, we find that p53 binding occurs predominantly within enhancers in both human and mouse model systems. The ability to modulate enhancer activity offers an additional layer of complexity to the p53 network and greatly expands the diversity of genomic elements directly regulated by p53.

  View details for DOI 10.1093/nar/gkv284

  View details for Web of Science ID 000355928800012

  View details for PubMedID 25883152

  View details for PubMedCentralID PMC4482066

• Cancer: A piece of the p53 puzzle. Nature Bieging, K. T., Attardi, L. D. 2015; 520 (7545): 37-38

  View details for DOI 10.1038/nature14374

  View details for PubMedID 25799989

• p53 suppresses muscle differentiation at the myogenin step in response to genotoxic stress CELL DEATH AND DIFFERENTIATION Yang, Z. J., Broz, D. K., Noderer, W. L., Ferreira, J. P., Overton, K. W., Spencer, S. L., Meyer, T., Tapscott, S. J., Attardi, L. D., Wang, C. L. 2015; 22 (4): 560-573

  Abstract

  Acute muscle injury and physiological stress from chronic muscle diseases and aging lead to impairment of skeletal muscle function. This raises the question of whether p53, a cellular stress sensor, regulates muscle tissue repair under stress conditions. By investigating muscle differentiation in the presence of genotoxic stress, we discovered that p53 binds directly to the myogenin promoter and represses transcription of myogenin, a member of the MyoD family of transcription factors that plays a critical role in driving terminal muscle differentiation. This reduction of myogenin protein is observed in G1-arrested cells and leads to decreased expression of late but not early differentiation markers. In response to acute genotoxic stress, p53-mediated repression of myogenin reduces post-mitotic nuclear abnormalities in terminally differentiated cells. This study reveals a mechanistic link previously unknown between p53 and muscle differentiation, and suggests new avenues for managing p53-mediated stress responses in chronic muscle diseases or during muscle aging.

  View details for DOI 10.1038/cdd.2014.189

  View details for Web of Science ID 000350857200007

  View details for PubMedID 25501595

  View details for PubMedCentralID PMC4356341

• Analysis of p53 Transactivation Domain Mutants Reveals Acad11 as a Metabolic Target Important for p53 Pro-Survival Function. Cell reports Jiang, D., Lagory, E. L., Kenzelmann Brož, D., Bieging, K. T., Brady, C. A., Link, N., Abrams, J. M., Giaccia, A. J., Attardi, L. D. 2015; 10 (7): 1096-1109

  Abstract

  The p53 tumor suppressor plays a key role in maintaining cellular integrity. In response to diverse stress signals, p53 can trigger apoptosis to eliminate damaged cells or cell-cycle arrest to enable cells to cope with stress and survive. However, the transcriptional networks underlying p53 pro-survival function are incompletely understood. Here, we show that in oncogenic-Ras-expressing cells, p53 promotes oxidative phosphorylation (OXPHOS) and cell survival upon glucose starvation. Analysis of p53 transcriptional activation domain mutants reveals that these responses depend on p53 transactivation function. Using gene expression profiling and ChIP-seq analysis, we identify several p53-inducible fatty acid metabolism-related genes. One such gene, Acad11, encoding a protein involved in fatty acid oxidation, is required for efficient OXPHOS and cell survival upon glucose starvation. This study provides new mechanistic insight into the pro-survival function of p53 and suggests that targeting this pathway may provide a strategy for therapeutic intervention based on metabolic perturbation.

  View details for DOI 10.1016/j.celrep.2015.01.043

  View details for PubMedID 25704813

• Analysis of p53 Transactivation Domain Mutants Reveals Acad11 as a Metabolic Target Important for p53 Pro-Survival Function CELL REPORTS Jiang, D., Lagory, E. L., Broz, D. K., Bieging, K. T., Brady, C. A., Link, N., Abrams, J. M., Giaccia, A. J., Attardi, L. D. 2015; 10 (7): 1096-1109

  Abstract

  The p53 tumor suppressor plays a key role in maintaining cellular integrity. In response to diverse stress signals, p53 can trigger apoptosis to eliminate damaged cells or cell-cycle arrest to enable cells to cope with stress and survive. However, the transcriptional networks underlying p53 pro-survival function are incompletely understood. Here, we show that in oncogenic-Ras-expressing cells, p53 promotes oxidative phosphorylation (OXPHOS) and cell survival upon glucose starvation. Analysis of p53 transcriptional activation domain mutants reveals that these responses depend on p53 transactivation function. Using gene expression profiling and ChIP-seq analysis, we identify several p53-inducible fatty acid metabolism-related genes. One such gene, Acad11, encoding a protein involved in fatty acid oxidation, is required for efficient OXPHOS and cell survival upon glucose starvation. This study provides new mechanistic insight into the pro-survival function of p53 and suggests that targeting this pathway may provide a strategy for therapeutic intervention based on metabolic perturbation.

  View details for DOI 10.1016/j.celrep.2015.01.043

  View details for Web of Science ID 000349918700007

• Guilty as CHARGED: p53's expanding role in disease CELL CYCLE Van Nostrand, J. L., Attardi, L. D. 2014; 13 (24): 3798-3807

  Abstract

  Unrestrained p53 activity during development, as occurs upon loss of the p53 negative regulators Mdm2 or Mdmx, causes early embryonic lethality. Surprisingly, co-expression of wild-type p53 and a transcriptionally-dead variant of p53, with mutations in both transactivation domains (p53(L25Q,W26S,F53Q,F54S)), also causes lethality, but later in gestation and in association with a host of very specific phenotypes reminiscent of a syndrome known as CHARGE. Molecular analyses revealed that wild-type p53 is inappropriately activated in p53(5,26,53,54/)(+) embryos, triggering cell-cycle arrest or apoptosis during development to cause CHARGE phenotypes. In addition, CHARGE syndrome is typically caused by mutations in the CHD7 chromatin remodeler, and we have shown that activated p53 contributes to phenotypes caused by CHD7-deficiency. Together, these studies provide new insight into CHARGE syndrome and expand our understanding of the role of p53 in diseases other than cancer.

  View details for DOI 10.4161/15384101.2014.987627

  View details for Web of Science ID 000348329600009

  View details for PubMedID 25483057

• Inappropriate p53 activation during development induces features of CHARGE syndrome NATURE Van Nostrand, J. L., Brady, C. A., Jung, H., Fuentes, D. R., Kozak, M. M., Johnson, T. M., Lin, C., Lin, C., Swiderski, D. L., Vogel, H., Bernstein, J. A., Attie-Bitach, T., Chang, C., Wysocka, J., Martin, D. M., Attardi, L. D. 2014; 514 (7521): 228-?

  Abstract

  CHARGE syndrome is a multiple anomaly disorder in which patients present with a variety of phenotypes, including ocular coloboma, heart defects, choanal atresia, retarded growth and development, genitourinary hypoplasia and ear abnormalities. Despite 70-90% of CHARGE syndrome cases resulting from mutations in the gene CHD7, which encodes an ATP-dependent chromatin remodeller, the pathways underlying the diverse phenotypes remain poorly understood. Surprisingly, our studies of a knock-in mutant mouse strain that expresses a stabilized and transcriptionally dead variant of the tumour-suppressor protein p53 (p53(25,26,53,54)), along with a wild-type allele of p53 (also known as Trp53), revealed late-gestational embryonic lethality associated with a host of phenotypes that are characteristic of CHARGE syndrome, including coloboma, inner and outer ear malformations, heart outflow tract defects and craniofacial defects. We found that the p53(25,26,53,54) mutant protein stabilized and hyperactivated wild-type p53, which then inappropriately induced its target genes and triggered cell-cycle arrest or apoptosis during development. Importantly, these phenotypes were only observed with a wild-type p53 allele, as p53(25,26,53,54)(/-) embryos were fully viable. Furthermore, we found that CHD7 can bind to the p53 promoter, thereby negatively regulating p53 expression, and that CHD7 loss in mouse neural crest cells or samples from patients with CHARGE syndrome results in p53 activation. Strikingly, we found that p53 heterozygosity partially rescued the phenotypes in Chd7-null mouse embryos, demonstrating that p53 contributes to the phenotypes that result from CHD7 loss. Thus, inappropriate p53 activation during development can promote CHARGE phenotypes, supporting the idea that p53 has a critical role in developmental syndromes and providing important insight into the mechanisms underlying CHARGE syndrome.

  View details for DOI 10.1038/nature13585

  View details for Web of Science ID 000342663100042

• Inappropriate p53 activation during development induces features of CHARGE syndrome. Nature Van Nostrand, J. L., Brady, C. A., Jung, H., Fuentes, D. R., Kozak, M. M., Johnson, T. M., Lin, C., Lin, C., Swiderski, D. L., Vogel, H., Bernstein, J. A., Attié-Bitach, T., Chang, C., Wysocka, J., Martin, D. M., Attardi, L. D. 2014; 514 (7521): 228-232

  Abstract

  CHARGE syndrome is a multiple anomaly disorder in which patients present with a variety of phenotypes, including ocular coloboma, heart defects, choanal atresia, retarded growth and development, genitourinary hypoplasia and ear abnormalities. Despite 70-90% of CHARGE syndrome cases resulting from mutations in the gene CHD7, which encodes an ATP-dependent chromatin remodeller, the pathways underlying the diverse phenotypes remain poorly understood. Surprisingly, our studies of a knock-in mutant mouse strain that expresses a stabilized and transcriptionally dead variant of the tumour-suppressor protein p53 (p53(25,26,53,54)), along with a wild-type allele of p53 (also known as Trp53), revealed late-gestational embryonic lethality associated with a host of phenotypes that are characteristic of CHARGE syndrome, including coloboma, inner and outer ear malformations, heart outflow tract defects and craniofacial defects. We found that the p53(25,26,53,54) mutant protein stabilized and hyperactivated wild-type p53, which then inappropriately induced its target genes and triggered cell-cycle arrest or apoptosis during development. Importantly, these phenotypes were only observed with a wild-type p53 allele, as p53(25,26,53,54)(/-) embryos were fully viable. Furthermore, we found that CHD7 can bind to the p53 promoter, thereby negatively regulating p53 expression, and that CHD7 loss in mouse neural crest cells or samples from patients with CHARGE syndrome results in p53 activation. Strikingly, we found that p53 heterozygosity partially rescued the phenotypes in Chd7-null mouse embryos, demonstrating that p53 contributes to the phenotypes that result from CHD7 loss. Thus, inappropriate p53 activation during development can promote CHARGE phenotypes, supporting the idea that p53 has a critical role in developmental syndromes and providing important insight into the mechanisms underlying CHARGE syndrome.

  View details for DOI 10.1038/nature13585

  View details for PubMedID 25119037

• Oncogenic transformation of diverse gastrointestinal tissues in primary organoid culture NATURE MEDICINE Li, X., Nadauld, L., Ootani, A., Corney, D. C., Pai, R. K., Gevaert, O., Cantrell, M. A., Rack, P. G., Neal, J. T., Chan, C. W., Yeung, T., Gong, X., Yuan, J., Wilhelmy, J., Robine, S., Attardi, L. D., Plevritis, S. K., Hung, K. E., Chen, C., Ji, H. P., Kuo, C. J. 2014; 20 (7): 769-777

  Abstract

  The application of primary organoid cultures containing epithelial and mesenchymal elements to cancer modeling holds promise for combining the accurate multilineage differentiation and physiology of in vivo systems with the facile in vitro manipulation of transformed cell lines. Here we used a single air-liquid interface culture method without modification to engineer oncogenic mutations into primary epithelial and mesenchymal organoids from mouse colon, stomach and pancreas. Pancreatic and gastric organoids exhibited dysplasia as a result of expression of Kras carrying the G12D mutation (Kras(G12D)), p53 loss or both and readily generated adenocarcinoma after in vivo transplantation. In contrast, primary colon organoids required combinatorial Apc, p53, Kras(G12D) and Smad4 mutations for progressive transformation to invasive adenocarcinoma-like histology in vitro and tumorigenicity in vivo, recapitulating multi-hit models of colorectal cancer (CRC), as compared to the more promiscuous transformation of small intestinal organoids. Colon organoid culture functionally validated the microRNA miR-483 as a dominant driver oncogene at the IGF2 (insulin-like growth factor-2) 11p15.5 CRC amplicon, inducing dysplasia in vitro and tumorigenicity in vivo. These studies demonstrate the general utility of a highly tractable primary organoid system for cancer modeling and driver oncogene validation in diverse gastrointestinal tissues.

  View details for DOI 10.1038/nm.3585

  View details for Web of Science ID 000338689500021

• Oncogenic transformation of diverse gastrointestinal tissues in primary organoid culture. Nature medicine Li, X., Nadauld, L., Ootani, A., Corney, D. C., Pai, R. K., Gevaert, O., Cantrell, M. A., Rack, P. G., Neal, J. T., Chan, C. W., Yeung, T., Gong, X., Yuan, J., Wilhelmy, J., Robine, S., Attardi, L. D., Plevritis, S. K., Hung, K. E., Chen, C. Z., Ji, H. P., Kuo, C. J. 2014

  Abstract

  The application of primary organoid cultures containing epithelial and mesenchymal elements to cancer modeling holds promise for combining the accurate multilineage differentiation and physiology of in vivo systems with the facile in vitro manipulation of transformed cell lines. Here we used a single air-liquid interface culture method without modification to engineer oncogenic mutations into primary epithelial and mesenchymal organoids from mouse colon, stomach and pancreas. Pancreatic and gastric organoids exhibited dysplasia as a result of expression of Kras carrying the G12D mutation (Kras(G12D)), p53 loss or both and readily generated adenocarcinoma after in vivo transplantation. In contrast, primary colon organoids required combinatorial Apc, p53, Kras(G12D) and Smad4 mutations for progressive transformation to invasive adenocarcinoma-like histology in vitro and tumorigenicity in vivo, recapitulating multi-hit models of colorectal cancer (CRC), as compared to the more promiscuous transformation of small intestinal organoids. Colon organoid culture functionally validated the microRNA miR-483 as a dominant driver oncogene at the IGF2 (insulin-like growth factor-2) 11p15.5 CRC amplicon, inducing dysplasia in vitro and tumorigenicity in vivo. These studies demonstrate the general utility of a highly tractable primary organoid system for cancer modeling and driver oncogene validation in diverse gastrointestinal tissues.

  View details for DOI 10.1038/nm.3585

  View details for PubMedID 24859528

• Unravelling mechanisms of p53-mediated tumour suppression NATURE REVIEWS CANCER Bieging, K. T., Mello, S. S., Attardi, L. D. 2014; 14 (5): 359-370

  Abstract

  p53 is a crucial tumour suppressor that responds to diverse stress signals by orchestrating specific cellular responses, including transient cell cycle arrest, cellular senescence and apoptosis, which are all processes associated with tumour suppression. However, recent studies have challenged the relative importance of these canonical cellular responses for p53-mediated tumour suppression and have highlighted roles for p53 in modulating other cellular processes, including metabolism, stem cell maintenance, invasion and metastasis, as well as communication within the tumour microenvironment. In this Opinion article, we discuss the roles of classical p53 functions, as well as emerging p53-regulated processes, in tumour suppression.

  View details for DOI 10.1038/nrc3711

  View details for Web of Science ID 000335562000013

  View details for PubMedID 24739573

  View details for PubMedCentralID PMC4049238

• Illuminating p53 function in cancer with genetically engineered mouse models SEMINARS IN CELL & DEVELOPMENTAL BIOLOGY Garcia, P. B., Attardi, L. D. 2014; 27: 74-85

  Abstract

  The key role of the p53 protein in tumor suppression is highlighted by its frequent mutation in human cancers and by the completely penetrant cancer predisposition of p53 null mice. Beyond providing definitive evidence for the critical function of p53 in tumor suppression, genetically engineered mouse models have offered numerous additional insights into p53 function. p53 knock-in mice expressing tumor-derived p53 mutants have revealed that these mutants display gain-of-function activities that actively promote carcinogenesis. The generation of p53 knock-in mutants with alterations in different domains of p53 has helped further elucidate the cellular and biochemical activities of p53, which is the most fundamental for tumor suppression. In addition, modulation of p53 post-translational modification (PTM) status by generating p53 knock-in mouse strains with mutations in p53 PTM sites has revealed a subtlety and complexity to p53 regulation. Analyses of mouse models perturbing upstream regulators of p53 have solidified the notion that the p53 pathway can be compromised by means other than direct p53 mutation. Finally, switchable p53 models that allow p53 reactivation in tumors have helped evaluate the potential of p53 restoration therapy for cancer treatment. Collectively, mouse models have greatly enhanced our understanding of physiological p53 function and will continue to provide new biological and clinical insights in future investigations.

  View details for DOI 10.1016/j.semcdb.2013.12.014

  View details for Web of Science ID 000337873100010

• Illuminating p53 function in cancer with genetically engineered mouse models. Seminars in cell & developmental biology Garcia, P. B., Attardi, L. D. 2014; 27: 74-85

  Abstract

  The key role of the p53 protein in tumor suppression is highlighted by its frequent mutation in human cancers and by the completely penetrant cancer predisposition of p53 null mice. Beyond providing definitive evidence for the critical function of p53 in tumor suppression, genetically engineered mouse models have offered numerous additional insights into p53 function. p53 knock-in mice expressing tumor-derived p53 mutants have revealed that these mutants display gain-of-function activities that actively promote carcinogenesis. The generation of p53 knock-in mutants with alterations in different domains of p53 has helped further elucidate the cellular and biochemical activities of p53, which is the most fundamental for tumor suppression. In addition, modulation of p53 post-translational modification (PTM) status by generating p53 knock-in mouse strains with mutations in p53 PTM sites has revealed a subtlety and complexity to p53 regulation. Analyses of mouse models perturbing upstream regulators of p53 have solidified the notion that the p53 pathway can be compromised by means other than direct p53 mutation. Finally, switchable p53 models that allow p53 reactivation in tumors have helped evaluate the potential of p53 restoration therapy for cancer treatment. Collectively, mouse models have greatly enhanced our understanding of physiological p53 function and will continue to provide new biological and clinical insights in future investigations.

  View details for DOI 10.1016/j.semcdb.2013.12.014

  View details for PubMedID 24394915

• Deconstructing p53 pathways in vivo Brady, C. A., Broz, D., Jiang, D., Mello, S., Bieging, K., Johnson, T. M., Jarvis, L. A., Kozak, M. M., Basak, S., Attardi, L. D. AMER ASSOC CANCER RESEARCH. 2013

  View details for DOI 10.1158/1538-7445.FBCR13-IA4

  View details for Web of Science ID 000209496600156

• TRP53 activates a global autophagy program to promote tumor suppression. Autophagy Kenzelmann Broz, D., Attardi, L. D. 2013; 9 (9): 1440-1442

  Abstract

  The mechanisms by which the TP53/TRP53 transcription factor acts as a tumor suppressor remain incompletely understood. To gain new insights into TP53/TRP53 biology, we used ChIP-seq and RNA-seq technologies to define global TRP53 transcriptional networks in primary cells subjected to DNA damage. Intriguingly, we identified a TRP53-regulated autophagy program, which can be coordinately regulated by the TRP53 family members TRP63 and TRP73 in certain settings. While autophagy is not involved in TRP53-dependent cell cycle arrest, it contributes to both TRP53-driven apoptosis in response to DNA damage and TRP53-mediated transformation suppression. Collectively, our genome-wide analyses reveal a profound role for TRP53 in regulating autophagy, through an extensive transcriptional network, and have demonstrated an important role for this program in promoting TRP53-mediated apoptosis and tumor suppression.

  View details for DOI 10.4161/auto.25833

  View details for PubMedID 23899499

• Not all p53 gain-of-function mutants are created equal. Cell death and differentiation Mello, S. S., Attardi, L. D. 2013; 20 (7): 855-857

  View details for DOI 10.1038/cdd.2013.53

  View details for PubMedID 23749181

• Tumor suppression: p53 alters immune surveillance to restrain liver cancer. Current biology Raj, N., Attardi, L. D. 2013; 23 (12): R527-30

  Abstract

  The p53 tumor suppressor governs multiple cell-intrinsic programs, including cell-cycle arrest and apoptosis, to curb neoplastic growth. A new study reveals that p53 also acts through a novel non-cell-autonomous mechanism, by stimulating the innate immune system to maintain tissue homeostasis and suppress tumorigenesis.

  View details for DOI 10.1016/j.cub.2013.04.076

  View details for PubMedID 23787049

• Engaging the p53 metabolic brake drives senescence. Cell research Jiang, D., Attardi, L. D. 2013; 23 (6): 739-740

  Abstract

  Emerging evidence suggests that the ability of p53 to regulate metabolism is important for its tumor suppressor activity. A recent study published in Nature reveals a novel connection between p53 and metabolism: p53 transcriptionally represses the expression of malic enzymes and associated NADPH production, which in turn triggers a positive feedback loop resulting in sustained p53 activation, cellular senescence, and tumor suppression.

  View details for DOI 10.1038/cr.2013.34

  View details for PubMedID 23478296

• Global genomic profiling reveals an extensive p53-regulated autophagy program contributing to key p53 responses GENES & DEVELOPMENT Broz, D. K., Mello, S. S., Bieging, K. T., Jiang, D., Dusek, R. L., Brady, C. A., Sidow, A., Attardi, L. D. 2013; 27 (9): 1016-1031

  View details for DOI 10.1101/gad.212282.112

  View details for Web of Science ID 000318700800008

• Global genomic profiling reveals an extensive p53-regulated autophagy program contributing to key p53 responses. Genes & development Kenzelmann Broz, D., Spano Mello, S., Bieging, K. T., Jiang, D., Dusek, R. L., Brady, C. A., Sidow, A., Attardi, L. D. 2013; 27 (9): 1016-1031

  Abstract

  The mechanisms by which the p53 tumor suppressor acts remain incompletely understood. To gain new insights into p53 biology, we used high-throughput sequencing to analyze global p53 transcriptional networks in primary mouse embryo fibroblasts in response to DNA damage. Chromatin immunoprecipitation sequencing reveals 4785 p53-bound sites in the genome located near 3193 genes involved in diverse biological processes. RNA sequencing analysis shows that only a subset of p53-bound genes is transcriptionally regulated, yielding a list of 432 p53-bound and regulated genes. Interestingly, we identify a host of autophagy genes as direct p53 target genes. While the autophagy program is regulated predominantly by p53, the p53 family members p63 and p73 contribute to activation of this autophagy gene network. Induction of autophagy genes in response to p53 activation is associated with enhanced autophagy in diverse settings and depends on p53 transcriptional activity. While p53-induced autophagy does not affect cell cycle arrest in response to DNA damage, it is important for both robust p53-dependent apoptosis triggered by DNA damage and transformation suppression by p53. Together, our data highlight an intimate connection between p53 and autophagy through a vast transcriptional network and indicate that autophagy contributes to p53-dependent apoptosis and cancer suppression.

  View details for DOI 10.1101/gad.212282.112

  View details for PubMedID 23651856

  View details for PubMedCentralID PMC3656320

• RB goes mitochondrial. Genes & development Attardi, L. D., Sage, J. 2013; 27 (9): 975-979

  Abstract

  The retinoblastoma tumor suppressor RB is well known for its capacity to restrict cell cycle progression at the G1/S transition of the cell cycle by controlling the transcription of cell cycle genes. In this issue of Genes & Development, Hilgendorf and colleagues (pp. 1003-1015) have identified a novel tumor suppressor function for RB independent of its role as a transcriptional regulator, in which RB directly activates the apoptosis regulator Bax at the mitochondria to promote cell death.

  View details for DOI 10.1101/gad.219451.113

  View details for PubMedID 23651852

  View details for PubMedCentralID PMC3656326

• Loss of the p53/p63 target PERP is an early event in oral carcinogenesis and correlates with higher rate of local relapse. Oral surgery, oral medicine, oral pathology and oral radiology Kong, C. S., Cao, H., Kwok, S., Nguyen, C. M., Jordan, R. C., Beaudry, V. G., Attardi, L. D., Le, Q. 2013; 115 (1): 95-103

  Abstract

  PERP is a p53/p63-regulated gene encoding a desmosomal protein that plays a critical role in cell-cell adhesion and tumor suppression.We evaluated PERP expression in different grades of oral dysplasia (34 cases) and at different stages of invasive squamous cell carcinoma (SCC), and correlated the latter with clinical outcome. A tissue microarray consisting of nondysplastic mucosa, carcinoma in situ, SCC, and nodal metastases from 33 patients with human papilloma virus-negative SCC was stained for PERP and E-cadherin.Complete loss of PERP expression was associated with worse local control in patients with SCC. The 5-year local control rate was 91% for patients with partial PERP loss versus 31% for those with complete loss (P = .01).This is the first study to show that loss of PERP expression correlates with the transition to SCC and with increased local relapse in patients with oral cavity SCC.

  View details for DOI 10.1016/j.oooo.2012.10.017

  View details for PubMedID 23217540

• Loss of the p53/p63 target PERP is an early event in oral carcinogenesis and correlates with higher rate of local relapse ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY ORAL RADIOLOGY Kong, C. S., Cao, H., Kwok, S., Nguyen, C. M., Jordan, R. C., Beaudry, V. G., Attardi, L. D., Quynh-Thu Le, Q. T. 2013; 115 (1): 95-103

  Abstract

  PERP is a p53/p63-regulated gene encoding a desmosomal protein that plays a critical role in cell-cell adhesion and tumor suppression.We evaluated PERP expression in different grades of oral dysplasia (34 cases) and at different stages of invasive squamous cell carcinoma (SCC), and correlated the latter with clinical outcome. A tissue microarray consisting of nondysplastic mucosa, carcinoma in situ, SCC, and nodal metastases from 33 patients with human papilloma virus-negative SCC was stained for PERP and E-cadherin.Complete loss of PERP expression was associated with worse local control in patients with SCC. The 5-year local control rate was 91% for patients with partial PERP loss versus 31% for those with complete loss (P = .01).This is the first study to show that loss of PERP expression correlates with the transition to SCC and with increased local relapse in patients with oral cavity SCC.

  View details for DOI 10.1016/j.oooo.2012.10.017

  View details for Web of Science ID 000312804800024

  View details for PubMedCentralID PMC3523282

• Unimpaired Skin Carcinogenesis in Desmoglein 3 Knockout Mice PLOS ONE Baron, S., Anabel Hoang, A., Vogel, H., Attardi, L. D. 2012; 7 (11)

  Abstract

  The contribution of adherens junction inactivation, typically by downregulation or mutation of the transmembrane core component E-cadherin, to cancer progression is well recognized. In contrast, the role of the desmosomal cadherin components of the related cell-cell adhesion junction, the desmosome, in cancer development has not been well explored. Here, we use mouse models to probe the functional role of desmosomal cadherins in carcinogenesis. Because mice lacking the desmosomal cadherin Desmoglein 3 (Dsg3) have revealed a crucial role for Dsg3 in cell-cell adhesion in stratified epithelia, we investigate the consequence of Dsg3 loss in two models of skin carcinogenesis. First, using Dsg3-/- keratinocytes, we show that these cells display adhesion defects in vitro and compromised tumor growth in allograft assays, suggesting that Dsg3 enables tumor formation in certain settings. In contrast, using an autochthonous model for SCC development in response to chronic UVB treatment, we discover a surprising lack of enhanced tumorigenesis in Dsg3-/- mice relative to controls, unlike mice lacking the desmosomal component Perp. Accordingly, there is no defect in the apoptotic response to UVB or enhanced immune cell infiltration upon Dsg3 loss that could promote tumorigenesis. Thus, Dsg3 does not display a clear function as a tumor suppressor in these mouse skin cancer models. Continued unraveling of the roles of Dsg3 and other desmosomal constituents in carcinogenesis in different contexts will be important for ultimately improving cancer diagnosis, prognostication, and treatment.

  View details for DOI 10.1371/journal.pone.0050024

  View details for PubMedID 23185521

• Deconstructing p53 transcriptional networks in tumor suppression TRENDS IN CELL BIOLOGY Bieging, K. T., Attardi, L. D. 2012; 22 (2): 97-106

  Abstract

  p53 is a pivotal tumor suppressor that induces apoptosis, cell-cycle arrest and senescence in response to stress signals. Although p53 transcriptional activation is important for these responses, the mechanisms underlying tumor suppression have been elusive. To date, no single or compound mouse knockout of specific p53 target genes has recapitulated the dramatic tumor predisposition that characterizes p53-null mice. Recently, however, analysis of knock-in mice expressing p53 transactivation domain mutants has revealed a group of primarily novel direct p53 target genes that may mediate tumor suppression in vivo. We present here an overview of well-known p53 target genes and the tumor phenotypes of the cognate knockout mice, and address the recent identification of new p53 transcriptional targets and how they enhance our understanding of p53 transcriptional networks central for tumor suppression.

  View details for DOI 10.1016/j.tcb.2011.10.006

  View details for Web of Science ID 000300870600004

  View details for PubMedID 22154076

  View details for PubMedCentralID PMC3541866

• Deficiency of the p53/p63 target Perp alters mammary gland homeostasis and promotes cancer BREAST CANCER RESEARCH Dusek, R. L., Bascom, J. L., Vogel, H., Baron, S., Borowsky, A. D., Bissell, M. J., Attardi, L. D. 2012; 14 (2)

  Abstract

  Perp is a transcriptional target of both p53 during DNA damage-induced apoptosis and p63 during stratified epithelial development. Perp-/- mice exhibit postnatal lethality associated with dramatic blistering of the epidermis and oral mucosa, reflecting a critical role in desmosome-mediated intercellular adhesion in keratinocytes. However, the role of Perp in tissue homeostasis in other p63-dependent stratified epithelial tissues is poorly understood. Given that p63 is essential for proper mammary gland development and that cell adhesion is fundamental for ensuring the proper architecture and function of the mammary epithelium, here we investigate Perp function in the mammary gland.Immunofluorescence and Western blot analysis were performed to characterize Perp expression and localization in the mouse mammary epithelium throughout development. The consequences of Perp deficiency for mammary epithelial development and homeostasis were examined by using in vivo mammary transplant assays. Perp protein levels in a variety of human breast cancer cell lines were compared with those in untransformed cells with Western blot analysis. The role of Perp in mouse mammary tumorigenesis was investigated by aging cohorts of K14-Cre/+;p53fl/fl mice that were wild-type or deficient for Perp. Mammary tumor latency was analyzed, and tumor-free survival was assessed using Kaplan-Meier analysis.We show that Perp protein is expressed in the mammary epithelium, where it colocalizes with desmosomes. Interestingly, although altering desmosomes through genetic inactivation of Perp does not dramatically impair mammary gland ductal development, Perp loss affects mammary epithelial homeostasis by causing the accumulation of inflammatory cells around mature mammary epithelium. Moreover, we show reduced Perp expression in many human breast cancer cell lines compared with untransformed cells. Importantly, Perp deficiency also promotes the development of mouse mammary cancer.Together, these observations demonstrate an important role for Perp in normal mammary tissue function and in mammary cancer suppression. In addition, our findings highlight the importance of desmosomes in cancer suppression and suggest the merit of evaluating Perp as a potential prognostic indicator or molecular target in breast cancer therapy.

  View details for DOI 10.1186/bcr3171

  View details for PubMedID 22515648

• Roles of p53 and pRB Tumor Suppressor Networks in Human Cancer: Insight from Studies in the Engineered Mouse GENETICALLY ENGINEERED MICE FOR CANCER RESEARCH: DESIGN, ANALYSIS, PATHWAYS, VALIDATION AND PRE-CLINICAL TESTING Sage, J., Attardi, L., Van Dyke, T., Green, J. E., Ried, T. 2012: 293–308

  View details for DOI 10.1007/978-0-387-69805-2_14

  View details for Web of Science ID 000303216200014

• Full p53 transcriptional activation potential is dispensable for tumor suppression in diverse lineages PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Jiang, D., Brady, C. A., Johnson, T. M., Lee, E. Y., Park, E. J., Scott, M. P., Attardi, L. D. 2011; 108 (41): 17123-17128

  Abstract

  Over half of all human cancers, of a wide variety of types, sustain mutations in the p53 tumor suppressor gene. Although p53 limits tumorigenesis through the induction of apoptosis or cell cycle arrest, its molecular mechanism of action in tumor suppression has been elusive. The best-characterized p53 activity in vitro is as a transcriptional activator, but the identification of numerous additional p53 biochemical activities in vitro has made it unclear which mechanism accounts for tumor suppression. Here, we assess the importance of transcriptional activation for p53 tumor suppression function in vivo in several tissues, using a knock-in mouse strain expressing a p53 mutant compromised for transcriptional activation, p53(25,26). p53(25,26) is severely impaired for the transactivation of numerous classical p53 target genes, including p21, Noxa, and Puma, but it retains the ability to activate a small subset of p53 target genes, including Bax. Surprisingly, p53(25,26) can nonetheless suppress tumor growth in cancers derived from the epithelial, mesenchymal, central nervous system, and lymphoid lineages. Therefore, full transactivation of most p53 target genes is dispensable for p53 tumor suppressor function in a range of tissue types. In contrast, a transcriptional activation mutant that is completely defective for transactivation, p53(25,26,53,54), fails to suppress tumor development. These findings demonstrate that transcriptional activation is indeed broadly critical for p53 tumor suppressor function, although this requirement reflects the limited transcriptional activity observed with p53(25,26) rather than robust transactivation of a full complement of p53 target genes.

  View details for DOI 10.1073/pnas.1111245108

  View details for Web of Science ID 000295973800051

  View details for PubMedID 21969549

  View details for PubMedCentralID PMC3193184

• The pro-longevity gene FoxO3 is a direct target of the p53 tumor suppressor ONCOGENE Renault, V. M., Thekkat, P. U., Hoang, K. L., WHITE, J. L., Brady, C. A., Broz, D. K., Venturelli, O. S., Johnson, T. M., Oskoui, P. R., Xuan, Z., Santo, E. E., Zhang, M. Q., Vogel, H., Attardi, L. D., Brunet, A. 2011; 30 (29): 3207-3221

  Abstract

  FoxO transcription factors have a conserved role in longevity, and act as tissue-specific tumor suppressors in mammals. Several nodes of interaction have been identified between FoxO transcription factors and p53, a major tumor suppressor in humans and mice. However, the extent and importance of the functional interaction between FoxO and p53 have not been fully explored. Here, we show that p53 regulates the expression of FoxO3, one of the four mammalian FoxO genes, in response to DNA damaging agents in both mouse embryonic fibroblasts and thymocytes. We find that p53 transactivates FoxO3 in cells by binding to a site in the second intron of the FoxO3 gene, a genomic region recently found to be associated with extreme longevity in humans. While FoxO3 is not necessary for p53-dependent cell cycle arrest, FoxO3 appears to modulate p53-dependent apoptosis. We also find that FoxO3 loss does not interact with p53 loss for tumor development in vivo, although the tumor spectrum of p53-deficient mice appears to be affected by FoxO3 loss. Our findings indicate that FoxO3 is a p53 target gene, and suggest that FoxO3 and p53 are part of a regulatory transcriptional network that may have an important role during aging and cancer.

  View details for DOI 10.1038/onc.2011.35

  View details for Web of Science ID 000293006800001

  View details for PubMedID 21423206

  View details for PubMedCentralID PMC3136551

• Distinct p53 Transcriptional Programs Dictate Acute DNA-Damage Responses and Tumor Suppression CELL Brady, C. A., Jiang, D., Mello, S. S., Johnson, T. M., Jarvis, L. A., Kozak, M. M., Broz, D. K., Basak, S., Park, E. J., McLaughlin, M. E., Karnezis, A. N., Attardi, L. D. 2011; 145 (4): 571-583

  Abstract

  The molecular basis for p53-mediated tumor suppression remains unclear. Here, to elucidate mechanisms of p53 tumor suppression, we use knockin mice expressing an allelic series of p53 transcriptional activation mutants. Microarray analysis reveals that one mutant, p53(25,26), is severely compromised for transactivation of most p53 target genes, and, moreover, p53(25,26) cannot induce G(1)-arrest or apoptosis in response to acute DNA damage. Surprisingly, p53(25,26) retains robust activity in senescence and tumor suppression, indicating that efficient transactivation of the majority of known p53 targets is dispensable for these pathways. In contrast, the transactivation-dead p53(25,26,53,54) mutant cannot induce senescence or inhibit tumorigenesis, like p53 nullizygosity. Thus, p53 transactivation is essential for tumor suppression but, intriguingly, in association with a small set of novel p53 target genes. Together, our studies distinguish the p53 transcriptional programs involved in acute DNA-damage responses and tumor suppression-a critical goal for designing therapeutics that block p53-dependent side effects of chemotherapy without compromising p53 tumor suppression.

  View details for DOI 10.1016/j.cell.2011.03.035

  View details for Web of Science ID 000290560800010

  View details for PubMedID 21565614

  View details for PubMedCentralID PMC3259909

• Desmosomes: new perpetrators in tumour suppression NATURE REVIEWS CANCER Dusek, R. L., Attardi, L. D. 2011; 11 (5): 317-323

  Abstract

  Adherens junctions, which are intercellular adhesive complexes that are crucial for maintaining epithelial homeostasis, are downregulated in many cancers to promote tumour progression. However, the role of desmosomes - adhesion complexes that are related to adherens junctions - in carcinogenesis has remained elusive. Recent studies using mouse genetic approaches have uncovered a role for desmosomes in tumour suppression, demonstrating that desmosome downregulation occurs before that of adherens junctions to drive tumour development and early invasion, suggesting a two-step model of adhesion dysfunction in cancer progression.

  View details for DOI 10.1038/nrc3051

  View details for Web of Science ID 000289779800009

  View details for PubMedID 21508970

• PERP regulates enamel formation via effects on cell-cell adhesion and gene expression JOURNAL OF CELL SCIENCE Jheon, A. H., Mostowfi, P., Snead, M. L., Ihrie, R. A., Sone, E., Pramparo, T., Attardi, L. D., Klein, O. D. 2011; 124 (5): 745-754

  Abstract

  Little is known about the role of cell-cell adhesion in the development of mineralized tissues. Here we report that PERP, a tetraspan membrane protein essential for epithelial integrity, regulates enamel formation. PERP is necessary for proper cell attachment and gene expression during tooth development, and its expression is controlled by P63, a master regulator of stratified epithelial development. During enamel formation, PERP is localized to the interface between the enamel-producing ameloblasts and the stratum intermedium (SI), a layer of cells subjacent to the ameloblasts. Perp-null mice display dramatic enamel defects, which are caused, in part, by the detachment of ameloblasts from the SI. Microarray analysis comparing gene expression in teeth of wild-type and Perp-null mice identified several differentially expressed genes during enamel formation. Analysis of these genes in ameloblast-derived LS8 cells upon knockdown of PERP confirmed the role for PERP in the regulation of gene expression. Together, our data show that PERP is necessary for the integrity of the ameloblast-SI interface and that a lack of Perp causes downregulation of genes that are required for proper enamel formation.

  View details for DOI 10.1242/jcs.078071

  View details for Web of Science ID 000287307000010

  View details for PubMedID 21285247

  View details for PubMedCentralID PMC3039019

• Loss of the p53/p63 Regulated Desmosomal Protein Perp Promotes Tumorigenesis PLOS GENETICS Beaudry, V. G., Jiang, D., Dusek, R. L., Park, E. J., Knezevich, S., Ridd, K., Vogel, H., Bastian, B. C., Attardi, L. D. 2010; 6 (10)

  Abstract

  Dysregulated cell-cell adhesion plays a critical role in epithelial cancer development. Studies of human and mouse cancers have indicated that loss of adhesion complexes known as adherens junctions contributes to tumor progression and metastasis. In contrast, little is known regarding the role of the related cell-cell adhesion junction, the desmosome, during cancer development. Studies analyzing expression of desmosome components during human cancer progression have yielded conflicting results, and therefore genetic studies using knockout mice to examine the functional consequence of desmosome inactivation for tumorigenesis are essential for elucidating the role of desmosomes in cancer development. Here, we investigate the consequences of desmosome loss for carcinogenesis by analyzing conditional knockout mice lacking Perp, a p53/p63 regulated gene that encodes an important component of desmosomes. Analysis of Perp-deficient mice in a UVB-induced squamous cell skin carcinoma model reveals that Perp ablation promotes both tumor initiation and progression. Tumor development is associated with inactivation of both of Perp's known functions, in apoptosis and cell-cell adhesion. Interestingly, Perp-deficient tumors exhibit widespread downregulation of desmosomal constituents while adherens junctions remain intact, suggesting that desmosome loss is a specific event important for tumorigenesis rather than a reflection of a general change in differentiation status. Similarly, human squamous cell carcinomas display loss of PERP expression with retention of adherens junctions components, indicating that this is a relevant stage of human cancer development. Using gene expression profiling, we show further that Perp loss induces a set of inflammation-related genes that could stimulate tumorigenesis. Together, these studies suggest that Perp-deficiency promotes cancer by enhancing cell survival, desmosome loss, and inflammation, and they highlight a fundamental role for Perp and desmosomes in tumor suppression. An understanding of the factors affecting cancer progression is important for ultimately improving the diagnosis, prognostication, and treatment of cancer.

  View details for DOI 10.1371/journal.pgen.1001168

  View details for PubMedID 20975948

• A Large Intergenic Noncoding RNA Induced by p53 Mediates Global Gene Repression in the p53 Response CELL Huarte, M., Guttman, M., Feldser, D., Garber, M., Koziol, M. J., Kenzelmann-Broz, D., Khalil, A. M., Zuk, O., Amit, I., Rabani, M., Attardi, L. D., Regev, A., Lander, E. S., Jacks, T., Rinn, J. L. 2010; 142 (3): 409-419

  Abstract

  Recently, more than 1000 large intergenic noncoding RNAs (lincRNAs) have been reported. These RNAs are evolutionarily conserved in mammalian genomes and thus presumably function in diverse biological processes. Here, we report the identification of lincRNAs that are regulated by p53. One of these lincRNAs (lincRNA-p21) serves as a repressor in p53-dependent transcriptional responses. Inhibition of lincRNA-p21 affects the expression of hundreds of gene targets enriched for genes normally repressed by p53. The observed transcriptional repression by lincRNA-p21 is mediated through the physical association with hnRNP-K. This interaction is required for proper genomic localization of hnRNP-K at repressed genes and regulation of p53 mediates apoptosis. We propose a model whereby transcription factors activate lincRNAs that serve as key repressors by physically associating with repressive complexes and modulate their localization to sets of previously active genes.

  View details for DOI 10.1016/j.cell.2010.06.040

  View details for Web of Science ID 000280609100018

  View details for PubMedID 20673990

  View details for PubMedCentralID PMC2956184

• p53 at a glance JOURNAL OF CELL SCIENCE Brady, C. A., Attardi, L. D. 2010; 123 (15): 2527-2532

  View details for DOI 10.1242/jcs.064501

  View details for Web of Science ID 000280172000001

  View details for PubMedID 20940128

  View details for PubMedCentralID PMC2912460

• In vivo analysis of p53 tumor suppressor function using genetically engineered mouse models CARCINOGENESIS Broz, D. K., Attardi, L. D. 2010; 31 (8): 1311-1318

  Abstract

  p53 is a crucial tumor suppressor, as evidenced by the high propensity for p53 mutation during human cancer development. Already more than a decade ago, p53 knockout mice confirmed that p53 is critical for preventing tumorigenesis. More recently, a host of p53 knock-in mouse strains has been generated, with the aim of either more precisely modeling p53 mutations in human cancer or better understanding p53's regulation and downstream activities. In the first category, several mouse strains expressing mutant p53 proteins corresponding to human-tumor-derived mutants have demonstrated that mutant p53 is not equivalent to loss of p53 but additionally exhibits gain-of-function properties, promoting invasive and metastatic phenotypes. The second class of p53 knock-in mouse models expressing engineered p53 mutants has also provided new insight into p53 function. For example, mice expressing p53 mutants lacking specific posttranslational modification sites have revealed that these modifications serve to modulate p53 responses in vivo in a cell-type- and stress-specific manner rather than being absolutely required for p53 stabilization and activation as suggested by in vitro experiments. Additionally, studies of p53 mouse models have established that both p53-driven cell-cycle arrest and apoptosis responses contribute to tumor suppression and that activation of p53 by oncogenic stress imposes an important barrier to tumorigenesis. Finally, the use of mouse strains expressing temporally regulatable p53 has demonstrated that p53 loss is not only required for tumor development but also required for tumor maintenance, suggesting that p53 restoration in human cancer patients may be a promising therapeutic strategy. These sophisticated p53 mouse models have taught us important lessons, and new mouse models will certainly continue to reveal interesting and perhaps surprising aspects of p53's complex biology.

  View details for DOI 10.1093/carcin/bgp331

  View details for Web of Science ID 000280703800001

  View details for PubMedID 20097732

  View details for PubMedCentralID PMC2915627

• Loss of the desmosomal component perp impairs wound healing in vivo. Dermatology research and practice Beaudry, V. G., Ihrie, R. A., Jacobs, S. B., Nguyen, B., Pathak, N., Park, E., Attardi, L. D. 2010; 2010: 759731-?

  Abstract

  Epithelial wound closure is a complex biological process that relies on the concerted action of activated keratinocytes and dermal fibroblasts to resurface and close the exposed wound. Modulation of cell-cell adhesion junctions is thought to facilitate cellular proliferation and migration of keratinocytes across the wound. In particular, desmosomes, adhesion complexes critical for maintaining epithelial integrity, are downregulated at the wound edge. It is unclear, however, how compromised desmosomal adhesion would affect wound reepithelialization, given the need for a delicate balance between downmodulating adhesive strength to permit changes in cellular morphology and maintaining adhesion to allow coordinated migration of keratinocyte sheets. Here, we explore the contribution of desmosomal adhesion to wound healing using mice deficient for the desmosomal component Perp. We find that Perp conditional knockout mice display delayed wound healing relative to controls. Furthermore, we determine that while loss of Perp compromises cell-cell adhesion, it does not impair keratinocyte proliferation and actually enhances keratinocyte migration in in vitro assays. Thus, Perp's role in promoting cell adhesion is essential for wound closure. Together, these studies suggest a role for desmosomal adhesion in efficient wound healing.

  View details for DOI 10.1155/2010/759731

  View details for PubMedID 20628490

  View details for PubMedCentralID PMC2902749

• Lessons on p53 from Mouse Models MOLECULAR BIOLOGY INTELLIGENCE UNIT P53 Jiang, D., Attardi, L. D., Ayed, A., Hupp, T. 2010: 19–35

  View details for Web of Science ID 000285983500002

• Differential PERP Regulation by TP63 Mutants Provides Insight Into AEC Pathogenesis AMERICAN JOURNAL OF MEDICAL GENETICS PART A Beaudry, V. G., Pathak, N., Koster, M. I., Attardi, L. D. 2009; 149A (9): 1952-1957

  Abstract

  Ankyloblepharon Ectodermal Dysplasia and Cleft Lip/Palate (AEC) or Hay-Wells Syndrome is an autosomal dominant disorder characterized by a variety of phenotypes in ectodermal derivatives, including severe skin erosions, ankyloblepharon, coarse and wiry hair, scalp dermatitis, and dystrophic nails. AEC is caused by mutations in the gene encoding the TP63 transcription factor, specifically in the Sterile Alpha Motif (SAM) domain. The exact mechanism, however, by which these specific TP63 mutations lead to the observed spectrum of phenotypes is unclear. Analysis of individual TP63 target genes provides a means to understand specific aspects of the phenotypes associated with AEC. PERP is a TP63 target critical for cell-cell adhesion due to its participation in desmosomal adhesion complexes. As PERP null mice display symptoms characteristic of ectodermal dysplasia syndromes, we hypothesized that PERP dysfunction might contribute to AEC. Using luciferase reporter assays, we demonstrate here that PERP induction is in fact compromised with some, but not all, AEC-patient derived TP63 mutants. Through analysis of skin biopsies from AEC patients, we show further that a subset of these display aberrant PERP expression, suggesting the possibility that PERP dysregulation is involved in the pathogenesis of this disease. These findings demonstrate that distinct AEC TP63 mutants can differentially compromise expression of downstream targets, providing a rationale for the variable spectra of symptoms seen in AEC patients. Elucidating how specific TP63 target genes contribute to the pathogenesis of AEC will ultimately help design novel approaches to diagnose and treat AEC.

  View details for DOI 10.1002/ajmg.a.32760

  View details for Web of Science ID 000269678800013

  View details for PubMedID 19353588

• SKP-ing TAp63: Stem Cell Depletion, Senescence, and Premature Aging CELL STEM CELL Beaudry, V. G., Attardi, L. D. 2009; 5 (1): 1-2

  Abstract

  The p53 family member p63 comprises multiple isoforms and is critical for stratified epithelial development. In this issue of Cell Stem Cell, by generating isoform-specific knockout mice, Su et al. (2009) reveal pivotal roles for TAp63 in the maintenance of dermal and epidermal precursors, genomic stability, and organismal longevity.

  View details for DOI 10.1016/j.stem.2009.06.015

  View details for Web of Science ID 000267879200001

  View details for PubMedID 19570504

• Loss of the Desmosomal Protein Perp Enhances the Phenotypic Effects of Pemphigus Vulgaris Autoantibodies JOURNAL OF INVESTIGATIVE DERMATOLOGY Nguyen, B., Dusek, R. L., Beaudry, V. G., Marinkovich, M. P., Attardi, L. D. 2009; 129 (7): 1710-1718

  Abstract

  Pemphigus vulgaris (PV) is an autoimmune bullous disease in which autoantibodies against proteins of the desmosomal adhesion complex perturb desmosomal function, leading to intercellular adhesion defects in the oral mucosa and skin. Previous studies have demonstrated a central role for downregulation of the desmosomal cadherin desmoglein 3 (DSG3) in the pathogenesis of PV. However, the effects of non-cadherin desmosomal proteins in modulating the cellular manifestations of PV remain poorly understood. Here, we characterize the expression and functional importance of Perp, a newly discovered tetraspan desmosomal protein, in PV. Our data demonstrate that PV autoantibodies disrupt Perp expression at the membrane and trigger its internalization along with DSG3 into the endosomal pathway, where it is ultimately targeted to the lysosome for degradation. We further show that Perp deficiency exacerbates the pathogenic effects of PV autoantibodies on keratinocytes by enhancing both the depletion of desmosomal DSG3 and intercellular adhesion defects. Together, our findings highlight the importance of non-cadherin desmosomal proteins in modulating PV phenotypes and provide new insight into Perp's role in the desmosome.

  View details for DOI 10.1038/jid.2008.419

  View details for PubMedID 19158843

• Ribosomal mutations cause p53-mediated dark skin and pleiotropic effects NATURE GENETICS McGowan, K. A., Li, J. Z., Park, C. Y., Beaudry, V., Tabor, H. K., Sabnis, A. J., Zhang, W., Fuchs, H., de Angelis, M. H., Myers, R. M., Attardi, L. D., Barsh, G. S. 2008; 40 (8): 963-970

  Abstract

  Mutations in genes encoding ribosomal proteins cause the Minute phenotype in Drosophila and mice, and Diamond-Blackfan syndrome in humans. Here we report two mouse dark skin (Dsk) loci caused by mutations in Rps19 (ribosomal protein S19) and Rps20 (ribosomal protein S20). We identify a common pathophysiologic program in which p53 stabilization stimulates Kit ligand expression, and, consequently, epidermal melanocytosis via a paracrine mechanism. Accumulation of p53 also causes reduced body size and erythrocyte count. These results provide a mechanistic explanation for the diverse collection of phenotypes that accompany reduced dosage of genes encoding ribosomal proteins, and have implications for understanding normal human variation and human disease.

  View details for DOI 10.1038/ng.188

  View details for Web of Science ID 000258026900012

  View details for PubMedID 18641651

  View details for PubMedCentralID PMC3979291

• The metastasis-associated gene Prl-3 is a p53 target involved in cell-cycle regulation MOLECULAR CELL Basak, S., Jacobs, S. B., Krieg, A. J., Pathak, N., Zeng, Q., Kaldis, P., Giaccia, A. J., Attardi, L. D. 2008; 30 (3): 303-314

  Abstract

  The p53 tumor suppressor restricts tumorigenesis through the transcriptional activation of target genes involved in cell-cycle arrest and apoptosis. Here, we identify Prl-3 (phosphatase of regenerating liver-3) as a p53-inducible gene. Whereas previous studies implicated Prl-3 in metastasis because of its overexpression in metastatic human colorectal cancer and its ability to promote invasiveness and motility, we demonstrate here that Prl-3 is an important cell-cycle regulator. Consistent with a role in DNA damage-induced cell-cycle arrest, Prl-3 overexpression induces G(1) arrest downstream of p53 by triggering a PI3K-Akt-activated negative feedback loop. Surprisingly, attenuation of Prl-3 expression also elicits an arrest response, suggesting that basal level Prl-3 expression is pivotal for normal cell-cycle progression. Our findings highlight key dose-dependent functions of Prl-3 in both positive and negative regulation of cell-cycle progression and provide insight into Prl-3's role in cancer progression.

  View details for DOI 10.1016/j.molcel.2008.04.002

  View details for Web of Science ID 000255761200008

  View details for PubMedID 18471976

• Mutations in ribosomal proteins cause p53-mediated dark skin International Investigative Dermatology Meeting McGowan, K., Li, J. Z., Beaudry, V., Tabor, H. K., Sabnis, A. J., Zhang, W., Fuchs, H., d'Angelis, M. H., Myers, R. M., Attardi, L. D., Barsh, G. S. NATURE PUBLISHING GROUP. 2008: S110–S110

  View details for Web of Science ID 000254353800656

• Genetics of dark skin: new genes, new pathways Barsh, G., McGowan, K., van Raamsdonk, C., Attardi, L., Bastian, B. WILEY-BLACKWELL. 2008: 248–48

  View details for Web of Science ID 000255061700038

• Knockin mice expressing a Chimeric p53 protein reveal mechanistic differences in how p53 triggers apoptosis and senescence PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Johnson, T. M., Meade, K., Pathak, N., Marques, M. R., Attardi, L. D. 2008; 105 (4): 1215-1220

  Abstract

  The contribution of transcriptional activation to the p53 effector functions critical for tumor suppression, apoptosis and cellular senescence, remains unclear because of p53's ability to regulate diverse cellular processes in a transactivation-independent manner. Dissociating the importance of transactivation from other p53 functions, including regulating transcriptional repression, DNA replication, homologous recombination, centrosome duplication, and mitochondrial function, has been difficult because of overlapping motifs for these functions in the amino terminus. To determine the relative contribution of these activities and transactivation to p53 function, we generated knockin mice expressing a p53 mutant lacking domains involved in these transactivation-independent functions, while remaining competent for transactivation through fusion to the Herpes Simplex Virus VP16 transactivation domain. This chimeric mutant, termed p53(VP16), robustly activates the transcription of a range of p53 targets involved in both apoptosis and senescence. Intriguingly, despite being transactivation-competent, this chimeric protein shows selectivity in p53 effector function in mouse fibroblasts, with a capacity to trigger senescence but not apoptosis under a variety of conditions. Our study highlights the central role of p53 transactivation for senescence while suggesting that transactivation is insufficient for apoptosis, and provides insight into the mechanisms by which p53 serves as a tumor suppressor.

  View details for DOI 10.1073/pnas.0706764105

  View details for Web of Science ID 000252873900025

  View details for PubMedID 18216268

  View details for PubMedCentralID PMC2234118

• Siva is an apoptosis-selective p53 target gene important for neuronal cell death CELL DEATH AND DIFFERENTIATION Jacobs, S. B., Basak, S., Murray, J. I., Pathak, N., Attardi, L. D. 2007; 14 (7): 1374-1385

  Abstract

  p53 plays a central role in neuronal cell death resulting from acute injury or disease. To define the pathway by which p53 triggers apoptosis, we used microarray analysis to identify p53 target genes specifically upregulated during apoptosis but not cell cycle arrest. This analysis identified a small subset of targets highly selective for the p53 apoptotic response, including Siva, a proapoptotic protein whose function is not well understood. Siva's expression pattern suggests that it plays an instructive role in apoptosis, and accordingly, we demonstrate that Siva is essential for p53-dependent apoptosis in cerebellar granule neurons. In addition, we determine that endogenous Siva is associated with the plasma membrane and that Caspase-8 and Bid are important for neuronal apoptosis. Our studies highlight the participation of membrane signaling events in p53's apoptotic program in primary neurons and have significant implications for understanding the mechanisms underlying pathogenesis after neuronal injury and in neurodegenerative diseases.

  View details for DOI 10.1038/sj.cdd.4402128

  View details for Web of Science ID 000247373400020

  View details for PubMedID 17464332

• A healthy tan? New England journal of medicine Barsh, G., Attardi, L. D. 2007; 356 (21): 2208-2210

  View details for PubMedID 17522405

• Dominant-negative but not gain-of-function effects of a p53.R270H mutation in mouse epithelium tissue after DNA damage CANCER RESEARCH Wijnhoven, S. W., Speksnijder, E. N., Liu, X., Zwart, E., vanOostrom, C. T., Beems, R. B., Hoogervorst, E. M., Schaap, M. M., Attardi, L. D., Jacks, T., van Steeg, H., Jonkers, J., de Vries, A. 2007; 67 (10): 4648-4656

  Abstract

  p53 alterations in human tumors often involve missense mutations that may confer dominant-negative or gain-of-function properties. Dominant-negative effects result in inactivation of wild-type p53 protein in heterozygous mutant cells and as such in a p53 null phenotype. Gain-of-function effects can directly promote tumor development or metastasis through antiapoptotic mechanisms or transcriptional activation of (onco)genes. Here, we show, using conditional mouse technology, that epithelium-specific heterozygous expression of mutant p53 (i.e., the p53.R270H mutation that is equivalent to the human hotspot R273H) results in an increased incidence of spontaneous and UVB-induced skin tumors. Expression of p53.R270H exerted dominant-negative effects on latency, multiplicity, and progression status of UVB-induced but not spontaneous tumors. Surprisingly, gain-of-function properties of p53.R270H were not detected in skin epithelium. Apparently, dominant-negative and gain-of-function effects of mutant p53 are highly tissue specific and become most manifest upon stabilization of p53 after DNA damage.

  View details for DOI 10.1158/0008-5472.CAN-06-4681

  View details for Web of Science ID 000246778500012

  View details for PubMedID 17510390

• P63, cell adhesion and survival CELL CYCLE Carroll, D. K., Brugge, J. S., Attardi, L. D. 2007; 6 (3): 255-261

  Abstract

  The development of stratified epithelia and their derivatives is a complex process requiring a multifaceted transcriptional program. p63, the p53-related transcription factor, is fundamental to this process. However, the underlying mechanisms by which p63 exerts its influence on stratified epithelial development and integrity remain elusive. Recent work from our laboratories has demonstrated that p63 mediates its effects on stratified epithelial function at least in part via its ability to regulate multiple aspects of epithelial cellular adhesion and survival. The identification of cell-cell and cell-matrix adhesion subprograms downstream of p63 provides an initial understanding of p63's role in epithelial development, integrity and homeostasis.

  View details for Web of Science ID 000245495300005

  View details for PubMedID 17297292

• Adult mice lacking the p53/p63 target gene Perp are not predisposed to spontaneous tumorigenesis but display features of ectodermal dysplasia syndromes CELL DEATH AND DIFFERENTIATION Ihrie, R. A., Bronson, R. T., Attardi, L. D. 2006; 13 (9): 1614-1618

  View details for DOI 10.1038/sj.cdd.4401871

  View details for Web of Science ID 000239920600020

  View details for PubMedID 16485031

• Dissecting p53 tumor suppressor function in vivo through the analysis of genetically modified mice CELL DEATH AND DIFFERENTIATION Johnson, T. M., Attardi, L. D. 2006; 13 (6): 902-908

  View details for DOI 10.1038/sj.cdd.4401902

  View details for Web of Science ID 000237703600006

  View details for PubMedID 16557272

• Genome-wide analysis of p53 under hypoxic conditions MOLECULAR AND CELLULAR BIOLOGY Hammond, E. M., Mandell, D. J., Salim, A., Krieg, A. J., Johnson, T. M., Shirazi, H. A., Attardi, L. D., Giaccia, A. J. 2006; 26 (9): 3492-3504

  Abstract

  Hypoxia is an important nongenotoxic stress that modulates the tumor suppressor activity of p53 during malignant progression. In this study, we investigated how genotoxic and nongenotoxic stresses regulate p53 association with chromatin, p53 transcriptional activity, and p53-dependent apoptosis. We found that genotoxic and nongenotoxic stresses result in the accumulation and binding of the p53 tumor suppressor protein to the same cognate binding sites in chromatin. However, it is the stress that determines whether downstream signaling is mediated by association with transcriptional coactivators. In contrast to p53 induced by DNA-damaging agents, hypoxia-induced p53 has primarily transrepression activity. Using extensive microarray analysis, we identified families of repressed targets of p53 that are involved in cell signaling, DNA repair, cell cycle control, and differentiation. Following our previous study on the contribution of residues 25 and 26 to p53-dependent hypoxia-induced apoptosis, we found that residues 25-26 and 53-54 and the polyproline- and DNA-binding regions are also required for both gene repression and the induction of apoptosis by p53 during hypoxia. This study defines a new role for residues 53 and 54 of p53 in regulating transrepression and demonstrates that 25-26 and 53-54 work in the same pathway to induce apoptosis through gene repression.

  View details for DOI 10.1128/MCB.26.9.3492-3504.2006

  View details for Web of Science ID 000236993300013

  View details for PubMedID 16611991

  View details for PubMedCentralID PMC1447427

• Dissecting p53 tumor suppressor function using transactivation mutant knock-in mice Attardi, L. D., Johnson, T. AMER ASSOC CANCER RESEARCH. 2006

  View details for Web of Science ID 000454606200657

• The requirement for Perp in postnatal viability and epithelial integrity reflects an intrinsic role in stratified epithelia JOURNAL OF INVESTIGATIVE DERMATOLOGY Marques, M. R., Ihrie, R. A., Horner, J. S., Attardi, L. D. 2006; 126 (1): 69-73

  Abstract

  Mice lacking the desmosome protein Perp exhibit blistering in their stratified epithelia and display postnatal lethality. However, it is unclear if these phenotypes are strictly related to Perp function in stratified epithelia, as Perp expression is not restricted to these tissues during embryogenesis, and certain desmosomal blistering diseases such as pemphigus vulgaris and pemphigus foliaceus have non-cell-intrinsic bases. Furthermore, we show here that Perp is expressed in the heart, raising the possibility that defects in heart function could account for lethality in the Perp-deficient mice. To determine conclusively if Perp function in stratified epithelia is crucial for postnatal survival and epithelial adhesion, we specifically ablated Perp in stratified epithelia by breeding conditional Perp knockout mice to keratin 5 (K5)-Cre transgenic mice. We found that the majority of mice lacking Perp in stratified epithelia die within 10 days after birth, accompanied by blistering and hyperproliferation in the epithelia, similar to the constitutive Perp null mice. Together, these findings indicate that Perp's requirement for both viability and epithelial integrity reflects a role in the stratified epithelial compartment.

  View details for DOI 10.1038/sj.jid.5700032

  View details for Web of Science ID 000238943900014

  View details for PubMedID 16417219

  View details for PubMedCentralID PMC2879258

• Probing p53 biological functions through the use of genetically engineered mouse models MUTATION RESEARCH-FUNDAMENTAL AND MOLECULAR MECHANISMS OF MUTAGENESIS Attardi, L. D., Donehower, L. A. 2005; 576 (1-2): 4-21

  Abstract

  The p53 tumor suppressor gene is rendered dysfunctional in the majority of human cancers. To model the effects of p53 dysfunction in an experimentally manipulable organismal context, genetically engineered inbred mice have been the models of choice. Transgenic and knock-out technologies have been utilized to generate an array of different p53 germ line alterations. As expected, many (though not all) of the mutant p53 mouse models are susceptible to enhanced spontaneous and carcinogen-induced tumors of a variety of types. A number of different variables affect the incidence and spectrum of tumors in p53 mutant mice. These include strain background, the nature of the p53 mutation, the presence of wild-type p53 (in addition to mutant p53), exposure to physical and chemical mutagens, or introduction of other cancer-associated genes into the mutant p53 background. In addition to their role in furthering our understanding of the mechanisms of cancer initiation and progression, these models have led to unexpected insights into p53 function in embryogenesis and aging. With the development of ever more sophisticated methods for manipulating the mouse genome, new p53 models are on the horizon, which should deliver advances that will provide not only important mechanistic insights but also discoveries of great clinical relevance.

  View details for DOI 10.1016/j.mrfmmm.2004.08.022

  View details for Web of Science ID 000231100900002

  View details for PubMedID 16038709

• Mice lacking the p53/p63 target gene perp are resistant to papilloma development CANCER RESEARCH Marques, M. R., Horner, J. S., Ihrie, R. A., Bronson, R. T., Attardi, L. D. 2005; 65 (15): 6551-6556

  Abstract

  Perp is a target of the p53 tumor suppressor involved in the DNA damage-induced apoptosis pathway. In addition, Perp is a target of the p53-related transcription factor p63 during skin development, where it participates in cell-cell adhesion mediated through desmosomes. Here we test the role of Perp in tumorigenesis in a two-step skin carcinogenesis model system. We find that mice lacking Perp in the skin are resistant to papilloma development, displaying fewer and smaller papillomas than wild-type mice. Proliferation levels, apoptotic indices and differentiation patterns are similar in the skin of treated Perp-deficient and wild-type mice. Instead, impaired adhesion through aberrant desmosome assembly may explain the diminished tumor development in the absence of Perp. These studies indicate that in certain contexts, Perp is required for efficient carcinogenesis and suggest a role for intact cell-cell adhesion in supporting tumor development in these settings.

  View details for Web of Science ID 000230837900013

  View details for PubMedID 16061634

• A new Perp in the lineup - Linking p63 and desmosomal adhesion CELL CYCLE Ihrie, R. A., Attardi, L. D. 2005; 4 (7): 873-876

  Abstract

  The process of stratified epithelial development depends upon a transcriptional program directed by the p53-related transcription factor p63. p63 is required for the commitment of the ectoderm to stratification and for the completion of terminal differentiation in stratified epithelia, and mutations in p63 have been identified in multiple developmental disorders affecting ectoderm-derived tissues. Recent work from our laboratory has determined that the p53 target gene Perp is required for the integrity of the stratified epithelia specified by p63, and that expression of Perp in these structures depends on the presence of p63. In these tissues, Perp is a critical component of the desmosome, a cell-cell adhesion complex whose constituents are frequently mutated in human diseases affecting the skin and hair. Perp's position downstream of p63 and p53, as well as its essential role in normal desmosome function, suggest that it, like other adhesion proteins, may be a target for mutation in human blistering diseases or cancer.

  View details for Web of Science ID 000230986600007

  View details for PubMedID 15970683

• Pathways connecting telomeres and p53 in senescence, apoptosis, and cancer BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Artandi, S. E., Attardi, L. D. 2005; 331 (3): 881-890

  Abstract

  The ends of eukaryotic chromosomes are protected by specialized structures termed telomeres that serve in part to prevent the chromosome end from activating a DNA damage response. However, this important function for telomeres in chromosome end protection can be lost as telomeres shorten with cell division in culture or in self-renewing tissues with advancing age. Impaired telomere function leads to induction of a DNA damage response and activation of the tumor suppressor protein p53. p53 serves a critical role in enforcing both senescence and apoptotic responses to dysfunctional telomeres. Loss of p53 creates a permissive environment in which critically short telomeres are inappropriately joined to generate chromosomal end-to-end fusions. These fused chromosomes result in cycles of chromosome fusion-bridge-breakage, which can fuel cancer initiation, especially in epithelial tissues, by facilitating changes in gene copy number.

  View details for Web of Science ID 000229135900023

  View details for PubMedID 15865944

• p53(QS) - An old mutant teaches us new tricks CELL CYCLE Johnson, T. M., Attardi, L. D. 2005; 4 (6): 731-734

  Abstract

  The p53 protein functions as a tumor suppressor, preventing aberrant cellular proliferation in response to various genotoxic and non-genotoxic stress signals. Although p53's ability to induce apoptosis is critical to its capacity to suppress tumorigenesis, the role of transcriptional activation in p53's apoptotic function has been highly controversial. To address this issue, our laboratory generated a p53 mutant knock-in mouse strain in which residues 25 and 26, previously shown to be critical for p53's transactivation function, were mutated from leucine and tryptophan to glutamine and serine, respectively. Our analysis of cells derived from these mice provided significant insight into p53 activity at both the molecular and cellular level. In particular, our data suggest that p53 utilizes discrete mechanisms to transactivate different target genes, and that p53 employs distinct mechanisms to induce apoptosis in response to different stresses. This p53QS mutant mouse strain represents a powerful means to dissect p53 function in vivo.

  View details for Web of Science ID 000229658100001

  View details for PubMedID 15908788

• Perp is a p63-regulated gene essential for epithelial integrity CELL Ihrie, R. A., Marques, M. R., Nguyen, B. T., Horner, J. S., Papazoglu, C., Bronson, R. T., Mills, A. A., Attardi, L. D. 2005; 120 (6): 843-856

  Abstract

  p63 is a master regulator of stratified epithelial development that is both necessary and sufficient for specifying this multifaceted program. We show here that Perp, a tetraspan membrane protein originally identified as an apoptosis-associated target of the p53 tumor suppressor, is the first direct target of p63 clearly involved in mediating this developmental program in vivo. During embryogenesis, Perp is expressed in an epithelial pattern, and its expression depends on p63. Perp-/- mice die postnatally, with dramatic blistering in stratified epithelia symptomatic of compromised adhesion. Perp localizes specifically to desmosomes, adhesion junctions important for tissue integrity, and numerous structural defects in desmosomes are observed in Perp-deficient skin, suggesting a role for Perp in promoting the stable assembly of desmosomal adhesive complexes. These findings demonstrate that Perp is a key effector in the p63 developmental program, playing an essential role in an adhesion subprogram central to epithelial integrity and homeostasis.

  View details for Web of Science ID 000228067500013

  View details for PubMedID 15797384

• Opinion - The role of apoptosis in cancer development and treatment response NATURE REVIEWS CANCER Brown, J. M., Attardi, L. D. 2005; 5 (3): 231-237

  Abstract

  The inactivation of programmed cell death, or apoptosis, is central to the development of cancer. This disabling of apoptotic responses might be a major contributor both to treatment resistance and to the observation that, in many tumours, apoptosis is not the main mechanism for the death of cancer cells in response to common treatment regimens. Importantly, this suggests that other modes of cell death are involved in the response to therapy.

  View details for DOI 10.1038/nrc1570

  View details for Web of Science ID 000227302700017

  View details for PubMedID 15738985

• The p53(QS) transactivation-deficient mutant shows stress-specific apoptotic activity and induces embryonic lethality NATURE GENETICS Johnson, T. M., Hammond, E. M., Giaccia, A., Attardi, L. D. 2005; 37 (2): 145-152

  Abstract

  The role of transcriptional activation in p53 function is highly controversial. To define this role in vivo, we generated a Trp53 knock-in construct encoding a protein carrying mutations of two residues that are crucial for transactivation (L25Q,W26S). Here we show that these mutations have selective effects on the biological functions of p53. Although its ability to activate various p53 target genes is largely compromised, the p53(QS) protein retains the ability to transactivate the gene Bax. The ability of the p53(QS) mutant protein to elicit a DNA damage-induced G1 cell cycle-arrest response is also partially impaired. p53(QS) has selective defects in its ability to induce apoptosis: it is completely unable to activate apoptosis in response to DNA damage, is partially unable to do so when subjected to serum deprivation and retains substantial apoptotic activity upon exposure to hypoxia. These findings suggest that p53 acts through distinct, stimulus-specific pathways to induce apoptosis. The importance of the biological activity of p53(QS) in vivo is underscored by our finding that expression of p53(QS), which cannot bind mdm2, induces embryonic lethality. Taken together, these results suggest that p53 has different mechanisms of action depending on specific contextual cues, which may help to clarify the function of p53 in preventing cancer.

  View details for DOI 10.1038/ng1498

  View details for Web of Science ID 000226690100020

  View details for PubMedID 15654339

• The role of p53-mediated apoptosis as a crucial anti-tumor response to genomic instability: lessons from mouse models MUTATION RESEARCH-FUNDAMENTAL AND MOLECULAR MECHANISMS OF MUTAGENESIS Attardi, L. D. 2005; 569 (1-2): 145-157

  Abstract

  Genomic instability is a major force driving human cancer development. A cellular safeguard against such genetic destabilization, which can ensue from defects in telomere maintenance, DNA repair, and checkpoint function, is activation of the p53 tumor suppressor protein, which commonly responds to these DNA damage signals by inducing apoptosis. If, however, p53 becomes inactivated, as is typical of many tumors and pre-cancerous lesions, then cells with compromised genome integrity pathways survive inappropriately, and the accrual of oncogenic lesions can fuel the carcinogenic process. Studies of mouse models have been instrumental in providing support for this idea. Mouse knockouts in genes important for telomere function, DNA damage checkpoint activation and DNA repair - both non-homologous end joining and homologous recombination - are prone to the development of genomic instability. As a consequence of these DNA damage signals, p53 becomes activated in cells of these mutant mice, leading to the induction of apoptosis, sometimes at the expense of organismal viability. This apoptotic response can be rescued through crosses to p53-deficient mice, but has dire consequences: mice predisposed to genomic instability and lacking p53 are susceptible to tumorigenesis. Thus p53-mediated apoptosis provides a crucial tumor suppressive mechanism to eliminate cells succumbing to genomic instability.

  View details for DOI 10.1016/j.mfrmmm.2004.04.019

  View details for Web of Science ID 000226211100012

  View details for PubMedID 15603759

• Developmental context determines latency of MYC-induced tumorigenesis PLOS BIOLOGY Beer, S., Zetterberg, A., Ihrie, R. A., McTaggart, R. A., Yang, Q. W., Bradon, N., Arvanitis, C., Attardi, L. D., Feng, S., Ruebner, B., Cardiff, R. D., Felsher, D. W. 2004; 2 (11): 1785-1798

  Abstract

  One of the enigmas in tumor biology is that different types of cancers are prevalent in different age groups. One possible explanation is that the ability of a specific oncogene to cause tumorigenesis in a particular cell type depends on epigenetic parameters such as the developmental context. To address this hypothesis, we have used the tetracycline regulatory system to generate transgenic mice in which the expression of a c-MYC human transgene can be conditionally regulated in murine hepatocytes. MYC's ability to induce tumorigenesis was dependent upon developmental context. In embryonic and neonatal mice, MYC overexpression in the liver induced marked cell proliferation and immediate onset of neoplasia. In contrast, in adult mice MYC overexpression induced cell growth and DNA replication without mitotic cell division, and mice succumbed to neoplasia only after a prolonged latency. In adult hepatocytes, MYC activation failed to induce cell division, which was at least in part mediated through the activation of p53. Surprisingly, apoptosis is not a barrier to MYC inducing tumorigenesis. The ability of oncogenes to induce tumorigenesis may be generally restrained by developmentally specific mechanisms. Adult somatic cells have evolved mechanisms to prevent individual oncogenes from initiating cellular growth, DNA replication, and mitotic cellular division alone, thereby preventing any single genetic event from inducing tumorigenesis.

  View details for DOI 10.1371/journal.pbio.0020332

  View details for Web of Science ID 000225160300011

  View details for PubMedID 15455033

  View details for PubMedCentralID PMC519000

• Increased sensitivity to UV radiation in mice with a p53 point mutation at Ser389 MOLECULAR AND CELLULAR BIOLOGY Bruins, W., Zwart, E., Attardi, L. D., Iwakuma, T., Hoogervorst, E. M., Beems, R. B., Miranda, B., van Oostrom, C. T., Van den Berg, J., van den Aardweg, G. J., Lozano, G., van Steeg, H., Jacks, T., de Vries, A. 2004; 24 (20): 8884-8894

  Abstract

  Phosphorylation is important for p53 protein stabilization and activation after DNA damage. Serine 389 of p53 is specifically phosphorylated after UV irradiation, whereas gamma radiation activates p53 through a different pathway. To study the in vivo significance of p53 phosphorylation at serine 389, we generated a physiological mouse model in which p53 phosphorylation at serine 389 is abolished by alanine substitution. Homozygous mutant p53.S389A mice are viable and have an apparently normal phenotype. However, cells isolated from these mice are partly compromised in transcriptional activation of p53 target genes and apoptosis after UV irradiation, whereas gamma radiation-induced responses are not affected. Moreover, p53.S389A mice show increased sensitivity to UV-induced skin tumor development, signifying the importance of serine 389 phosphorylation for the tumor-suppressive function of p53.

  View details for DOI 10.1128/mcb.24.20.8884-8894.2004

  View details for Web of Science ID 000224239100008

  View details for PubMedID 15456863

  View details for PubMedCentralID PMC517897

• Perp-etrating p53-dependent apoptosis CELL CYCLE Ihrie, R. A., Attardi, L. D. 2004; 3 (3): 267-269

  Abstract

  The induction of apoptosis is a fundamental mechanism by which the p53 transcriptional activator protein suppresses tumor development. Recently, the roles of several p53 target genes in mediating the p53 apoptotic response have been queried through loss-of-function analysis with knockout mouse models. These studies have demonstrated that the p53 targets Noxa, Puma, and Perp play cell type-specific roles in p53-mediated apoptosis. Perp, a tetraspan protein localizing to the plasma membrane, rather than to mitochondria, is a novel type of p53 effector that may stimulate apoptosis through a different mechanism from the BH3-containing proteins Noxa, Puma, and Bax.

  View details for Web of Science ID 000222361400012

  View details for PubMedID 14726658

• Activation of the p53-dependent G1 checkpoint response in mouse embryo fibroblasts depends on the specific DNA damage inducer ONCOGENE Attardi, L. D., de Vries, A., Jacks, T. 2004; 23 (4): 973-980

  Abstract

  The p53 tumor suppressor protein inhibits proliferation by inducing either cell cycle arrest or apoptosis in response to cellular stresses. Mouse embryo fibroblasts (MEFs) provide a primary cell model system in which to examine both functions of p53. MEFs treated with gamma-rays undergo p53-dependent G1 arrest, while oncogene-expressing MEFs treated with a variety of DNA-damaging agents undergo p53-dependent apoptosis. Although the p53-dependent G1 arrest checkpoint response to gamma-rays in MEFs has been well characterized, the response to other DNA-damaging agents has not. Here, we examine the effects of commonly utilized chemotherapeutics, including doxorubicin, etoposide, and cisplatin, on cell cycle arrest in MEFs, and we define the p53 dependence of these effects. In addition, we examine the response of MEFs to ultraviolet light (UVC), as a representative agent acting by inducing pyrimidine dimers. Although p53 is clearly activated by all the agents examined, as measured by p21 induction, there are surprising differences in the activities of these agents. For example, doxorubicin but not cisplatin can effectively induce a p53-dependent G1 arrest. UVC, in contrast, induces a p53-independent G1 arrest response. Thus, the exact response of cells to DNA damage depends on the specific agent used.

  View details for DOI 10.1038/sj.onc.1207026

  View details for Web of Science ID 000188486600013

  View details for PubMedID 14749764

• Conquering the complexity of p53 NATURE GENETICS Attardi, L. D., DePinho, R. A. 2004; 36 (1): 7-8

  View details for DOI 10.1038/ng0104-7

  View details for Web of Science ID 000187666800004

  View details for PubMedID 14702030

• Multiple response elements and differential p53 binding control perp expression during apoptosis MOLECULAR CANCER RESEARCH Reczek, E. E., Flores, E. R., Tsay, A. S., Attardi, L. D., Jacks, T. 2003; 1 (14): 1048-1057

  Abstract

  The p53 tumor suppressor gene responds to cellular stress by activating either cell cycle arrest or apoptosis. A growing number of target genes involved in each of these pathways have been identified. However, the mechanism by which the apoptosis versus arrest decision is made remains to be elucidated. Perp is a proapoptotic target gene of p53 expressed to high levels in apoptotic cells compared with those undergoing cell cycle arrest. This pattern of expression is unusual among p53 target genes, many of which are induced to similar levels during arrest and apoptosis. Here, we describe the regulation of the Perp gene by p53 through at least three response elements in the Perp promoter and first intron. These sites are occupied in vivo in E1A-expressing mouse embryo fibroblasts undergoing apoptosis but not cell cycle arrest, in contrast to the p21 5' response element, which is occupied during both. The apoptosis-deficient p53 point mutant, p53V143A, displays a selective deficit in binding to the Perp elements, demonstrating that p53 can distinguish between Perp and p21 at the level of DNA binding. These results provide mechanistic insight into the selective expression of Perp during apoptosis and may provide a useful model for studying the p53-dependent cell cycle arrest versus apoptosis decision.

  View details for Web of Science ID 000187889000007

  View details for PubMedID 14707288

• Perp is a mediator of p53-dependent apoptosis in diverse cell types CURRENT BIOLOGY Ihrie, R. A., Reczek, E., Horner, J. S., Khachatrian, L., Sage, J., Jacks, T., Attardi, L. D. 2003; 13 (22): 1985-1990

  Abstract

  The induction of apoptosis by the p53 protein is critical for its activity as a tumor suppressor. Although it is clear that p53 induces apoptosis at least in part by direct transcriptional activation of target genes, the set of p53 target genes that mediate p53 function in apoptosis in vivo remains to be well defined. The Perp (p53 apoptosis effector related to PMP-22) gene is highly expressed in cells undergoing p53-dependent apoptosis as compared to cells undergoing p53-dependent G1 arrest. Perp is a direct p53 target, and its overexpression is sufficient to induce cell death in fibroblasts, implicating it as an important component of p53 apoptotic function. Here, through the generation of Perp-deficient mice, we analyze the role of Perp in the p53 apoptosis pathway in multiple primary cell types by comparing the cell death responses of Perp null cells to those of wild-type and p53 null cells. These experiments demonstrate the involvement of Perp in p53-mediated cell death in thymocytes and neurons but not in E1A-expressing MEFs, indicating a cell type-specific role for Perp in the p53 cell death pathway. In addition, we show that Perp is not required for proliferation-associated functions of p53. Thus, Perp selectively mediates the p53 apoptotic response, and the requirement for Perp is dictated by cellular context.

  View details for DOI 10.1016/j.cub.2003.10.055

  View details for Web of Science ID 000186558100026

  View details for PubMedID 14614825

• Targeted disruption of the three Rb-related genes leads to loss of G(1) control and immortalization GENES & DEVELOPMENT Sage, J., Mulligan, G. J., Attardi, L. D., Miller, A., Chen, S. Q., Williams, B., Theodorou, E., Jacks, T. 2000; 14 (23): 3037-3050

  Abstract

  The retinoblastoma protein, pRB, and the closely related proteins p107 and p130 are important regulators of the mammalian cell cycle. Biochemical and genetic studies have demonstrated overlapping as well as distinct functions for the three proteins in cell cycle control and mouse development. However, the role of the pRB family as a whole in the regulation of cell proliferation, cell death, or cell differentiation is not known. We generated embryonic stem (ES) cells and other cell types mutant for all three genes. Triple knock-out mouse embryonic fibroblasts (TKO MEFs) had a shorter cell cycle than wild-type, single, or double knock-out control cells. TKO cells were resistant to G(1) arrest following DNA damage, despite retaining functional p53 activity. They were also insensitive to G(1) arrest signals following contact inhibition or serum starvation. Finally, TKO MEFs did not undergo senescence in culture and do possess some characteristics of transformed cells. Our results confirm the essential role of the Rb family in the control of the G(1)/S transition, place the three Rb family members downstream of multiple cell cycle control pathways, and further the link between loss of cell cycle control and tumorigenesis.

  View details for Web of Science ID 000165788600011

  View details for PubMedID 11114892

• PERP, an apoptosis-associated target of p53, is a novel member of the PMP-22/gas3 family GENES & DEVELOPMENT Attardi, L. D., Reczek, E. E., Cosmas, C., Demicco, E. G., McCurrach, M. E., Lowe, S. W., Jacks, T. 2000; 14 (6): 704-718

  Abstract

  The p53 tumor suppressor activates either cell cycle arrest or apoptosis in response to cellular stress. Mouse embryo fibroblasts (MEFs) provide a powerful primary cell system to study both p53-dependent pathways. Specifically, in response to DNA damage, MEFs undergo p53-dependent G(1) arrest, whereas MEFs expressing the adenovirus E1A oncoprotein undergo p53-dependent apoptosis. As the p53-dependent apoptosis pathway is not well understood, we sought to identify apoptosis-specific p53 target genes using a subtractive cloning strategy. Here, we describe the characterization of a gene identified in this screen, PERP, which is expressed in a p53-dependent manner and at high levels in apoptotic cells compared with G(1)-arrested cells. PERP induction is linked to p53-dependent apoptosis, including in response to E2F-1-driven hyperproliferation. Furthermore, analysis of the PERP promoter suggests that PERP is directly activated by p53. PERP shows sequence similarity to the PMP-22/gas3 tetraspan membrane protein implicated in hereditary human neuropathies such as Charcot-Marie-Tooth. Like PMP-22/gas3, PERP is a plasma membrane protein, and importantly, its expression causes cell death in fibroblasts. Taken together, these data suggest that PERP is a novel effector of p53-dependent apoptosis.

  View details for Web of Science ID 000086224700008

  View details for PubMedID 10733530

• The role of p53 in tumour suppression: lessons from mouse models CELLULAR AND MOLECULAR LIFE SCIENCES Attardi, L. D., Jacks, T. 1999; 55 (1): 48-63

  Abstract

  The use of mouse models has greatly contributed to our understanding of the role of p53 in tumour suppression. Mice homozygous for a deletion in the p53 gene develop tumours at high frequency, providing essential evidence for the importance of p53 as a tumour suppressor. Additionally, crossing these knockout mice or transgenic expression p53 dominant negative alleles with other tumour-prone mouse strains has allowed the effect of p53 loss on tumour development to be examined further. In a variety of mouse models, absence of p53 facilitates tumorigenesis, thus providing a means to study how the lack of p53 enhances tumour development and to define genetic pathways of p53 action. Depending on the particular model system, loss of p53 either results in deregulated cell-cycle entry or aberrant apoptosis (programmed cell death), confirming results found in cell culture systems and providing insight into in vitro function of p53. Finally, as p53 null mice rapidly develop tumours, they are useful for evaluating agents for either chemopreventative or therapeutic activities.

  View details for Web of Science ID 000078544100006

  View details for PubMedID 10065151

• Absence of p53 in a mouse mammary tumor model promotes tumor cell proliferation without affecting apoptosis CELL GROWTH & DIFFERENTIATION Jones, J. M., Attardi, L., Godley, L. A., Laucirica, R., Medina, D., Jacks, T., Varmus, H. E., Donehower, L. A. 1997; 8 (8): 829-838

  Abstract

  Loss or mutation of p53 may have multiple biological and genetic effects that result in accelerated tumor progression. Loss of p53 in some tumors has been correlated with a marked decrease in tumor cell apoptosis. p53 loss may also accelerate tumor growth through an increase in cell proliferation rates. To examine the effects of p53 loss on tumor progression in a controlled experimental context, we previously crossed p53-deficient mice to mammary tumor-susceptible Wnt-1 transgenic (TG) mice. The resulting female Wnt-1 TG offspring of this cross all developed mammary tumors, regardless of p53 status (p53+/+, p53+/-, or p53-/-). However, female p53-/- Wnt-1 TG mice developed tumors much sooner than their p53+/+ counterparts. In this report, we demonstrate that the average growth rates of tumors missing (p53-/-) or losing p53 (p53+/- with loss of heterozygosity) are accelerated compared to tumors with both wild-type p53 alleles (p53+/+). This accelerated growth rate appears to be due primarily to increases in rates of tumor cell proliferation. Tumor cell apoptotic levels were modest and were not measurably different in the presence or absence of wild-type p53. These results differ substantially from other mouse tumor models in which p53 loss was closely correlated with accelerated growth rates through attenuated apoptosis. Thus, the mechanisms by which p53 loss influences tumor progression may differ, depending on the tissue type and/or the oncogenic pathways involved.

  View details for Web of Science ID A1997XQ82300001

  View details for PubMedID 9269892

• Transcriptional activation by p53, but not induction of the p21 gene, is essential for oncogene-mediated apoptosis EMBO JOURNAL Attardi, L. D., Lowe, S. W., Brugarolas, J., Jacks, T. 1996; 15 (14): 3693-3701

  Abstract

  The p53 tumor suppressor limits cellular proliferation by inducing either G1 arrest or apoptosis, depending on the cellular context. To determine if these pathways are mechanistically distinct, we have examined the effects of different p53 mutants in p53 null primary mouse embryo fibroblasts. We chose this system as it is highly physiological and ensures that the interpretation of the results will not be confounded by the presence of endogenous p53 or oncoproteins which target p53. Using single cell microinjection assays for both G1 arrest and apoptosis, with loss-of-function and chimeric gain-of-function mutants, we have demonstrated that transcriptional activation is critical for both processes. Replacement of the p53 activation domain with that of VP16, or replacement of the p53 oligomerization domain with that of GCN4, reconstituted both G1 arrest and apoptosis activities. However, despite the importance of transcriptional activation in both processes, the target gene requirements are different. The p21 cyclin-dependent kinase inhibitor, which has been shown to be a direct target of p53 and a component of the radiation-induced G1 arrest response, is dispensable for oncogene-induced apoptosis, suggesting that these two p53-dependent transcriptional pathways are distinct.

  View details for Web of Science ID A1996UY92200023

  View details for PubMedID 8758936

• Transcriptional Activation by p53, but not Induction of the p21 Gene, is Essential for Oncogene-Mediated Apoptosis Embo J Attardi, L.D., S.W. Lowe, J. Brugarolas, T. Jacks 1996; 15
• A SUBSET OF P53-DEFICIENT EMBRYOS EXHIBIT EXENCEPHALY NATURE GENETICS Sah, V. P., Attardi, L. D., Mulligan, G. J., Williams, B. O., Bronson, R. T., Jacks, T. 1995; 10 (2): 175-180

  Abstract

  Defects in neural tube formation are among the most common malformations leading to infant mortality. Although numerous genetic loci appear to contribute to the defects observed in humans and in animal model systems, few of the genes involved have been characterized at the molecular level. Mice lacking the p53 tumour suppressor gene are predisposed to tumours, but the viability of these animals indicates that p53 function is not essential for embryonic development. Here, we demonstrate that a fraction of p53-deficient embryos in fact do not develop normally. These animals display defects in neural tube closure resulting in an overgrowth of neural tissue in the region of the mid-brain, a condition known as exencephaly.

  View details for Web of Science ID A1995RA85700014

  View details for PubMedID 7663512

• ASSEMBLY OF RECOMBINANT TFIID REVEALS DIFFERENTIAL COACTIVATOR REQUIREMENTS FOR DISTINCT TRANSCRIPTIONAL ACTIVATORS CELL Chen, J. L., Attardi, L. D., Verrijzer, C. P., Yokomori, K., Tjian, R. 1994; 79 (1): 93-105

  Abstract

  We previously reported that transcriptional regulators can bind selected TAF subunits of the TFIID complex. However, the specificity and function of individual TAFs in mediating transcriptional activation remained unknown. Here we report the in vitro assembly and transcriptional properties of TBP-TAF complexes reconstituted from the nine recombinant subunits of Drosophila TFIID. A minimal complex containing TBP and TAFII250 directs basal but not activator-responsive transcription. By contrast, reconstituted holo-TFIID supports activation by an assortment of activators. The activator NTF-1, which binds TAFII150, stimulates transcription with a complex containing only TBP, TAFII250, and TAFII150, whereas Sp1 binds and additionally requires TAFII110 for activation. Interestingly, TAFII150 enhances Sp1 activation even though this subunit does not bind directly to Sp1. These results establish that specific subcomplexes of TFIID can mediate activation by different classes of activators and suggest that TAFs perform multiple functions during activation.

  View details for Web of Science ID A1994PK58500011

  View details for PubMedID 7923382