Livia Ulicna PhD, is a Postdoctoral Research Fellow working with Dr. Capucine Van Rechem in the Department of Pathology at Stanford School of Medicine. Dr. Ulicna received her MSc in Molecular Biology and PhD in Cell and Developmental Biology. As Postdoctoral Fellow, she is interested in non-canonical roles of chromatin modifying enzymes with particular focus on protein synthesis in cancer.
Doctor of Philosophy, Univerzita Karlova (2018)
Master of Science, Comenius University (2013)
Bachelor of Science, Comenius University (2011)
Capucine van Rechem, Postdoctoral Faculty Sponsor
Nuclear Phosphoinositides-Versatile Regulators of Genome Functions.
2019; 8 (7)
The many functions of phosphoinositides in cytosolic signaling were extensively studied; however, their activities in the cell nucleus are much less clear. In this review, we summarize data about their nuclear localization and metabolism, and review the available literature on their involvements in chromatin remodeling, gene transcription, and RNA processing. We discuss the molecular mechanisms via which nuclear phosphoinositides, in particular phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2), modulate nuclear processes. We focus on PI(4,5)P2's role in the modulation of RNA polymerase I activity, and functions of the nuclear lipid islets-recently described nucleoplasmic PI(4,5)P2-rich compartment involved in RNA polymerase II transcription. In conclusion, the high impact of the phosphoinositide-protein complexes on nuclear organization and genome functions is only now emerging and deserves further thorough studies.
View details for DOI 10.3390/cells8070649
View details for PubMedID 31261688
Phospholipids and inositol phosphates linked to the epigenome.
Histochemistry and cell biology
Even though the majority of knowledge about phospholipids comes from their cytoplasmic functions, in the last decade, it has been shown that nuclear phospholipids and their building blocks, inositol phosphates, have many important roles in the cell nucleus. There are clear connections of phospholipids with the regulation of gene expression and chromatin biology, however, this review focuses on less known functions of nuclear phospholipids in connection with the epigenome regulation. In particular, we highlight the roles of nuclear phospholipids and inositol phosphates that involve histone modifications, such as acetylation or methylation, tightly connected with the cell physiology. This demonstrates the importance of nuclear phospholipids in the regulation of cellular processes, and should encourage further research of nuclear phospholipids and inositol phosphates.
View details for DOI 10.1007/s00418-018-1690-9
View details for PubMedID 29982846
Nuclear phosphatidylinositol 4,5-bisphosphate islets contribute to efficient RNA polymerase II-dependent transcription.
Journal of cell science
2018; 131 (8)
This paper describes a novel type of nuclear structure - nuclear lipid islets (NLIs). They are of 40-100 nm with a lipidic interior, and phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] molecules comprise a significant part of their surface. Most of NLIs have RNA at the periphery. Consistent with that, RNA is required for their integrity. The NLI periphery is associated with Pol II transcription machinery, including the largest Pol II subunit, transcription factors and NM1 (also known as NMI). The PtdIns(4,5)P2-NM1 interaction is important for Pol II transcription, since NM1 knockdown reduces the Pol II transcription level, and the overexpression of wild-type NM1 [but not NM1 mutated in the PtdIns(4,5)P2-binding site] rescues the transcription. Importantly, Pol II transcription is dependent on NLI integrity, because an enzymatic reduction of the PtdIns(4,5)P2 level results in a decrease of the Pol II transcription level. Furthermore, about half of nascent transcripts localise to NLIs, and transcriptionally active transgene loci preferentially colocalise with NLIs. We hypothesize that NLIs serve as a structural platform that facilitates the formation of Pol II transcription factories, thus participating in the formation of nuclear architecture competent for transcription.
View details for DOI 10.1242/jcs.211094
View details for PubMedID 29507116
PIP2 epigenetically represses rRNA genes transcription interacting with PHF8
BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR AND CELL BIOLOGY OF LIPIDS
2018; 1863 (3): 266–75
Phosphoinositides are present in the plasma membrane, cytoplasm and inside the cell nucleus. Here we identify phosphatidylinositol-4,5-bisphosphate (PIP2) as a regulator of rRNA genes transcription at the epigenetic level. We show that PIP2 directly interacts with histone lysine demethylase PHF8 (PHD finger protein 8) and represses demethylation of H3K9me2 through this interaction. We identify the C-terminal K/R-rich motif as PIP2-binding site within PHF8, and address the function of this PIP2-PHF8 complex. PIP2-binding mutant of PHF8 has increased the activity of rDNA promoter (20%) and expression of pre-rRNA genes (47S-100%; 45S-66%). Furthermore, trypsin digestion reveals a potential conformational change of PHF8 upon PIP2 binding. These observations identify the function of nuclear PIP2, and suggest that PIP2 contributes to the fine-tuning of rDNA transcription.
View details for DOI 10.1016/j.bbalip.2017.12.008
View details for Web of Science ID 000424960400004
View details for PubMedID 29246768
Multiple Aspects of PIP2 Involvement in C. elegans Gametogenesis
Int J Mol Sci
2018; 19 (9)
View details for DOI 10.3390/ijms19092679
Tools for visualization of phosphoinositides in the cell nucleus
HISTOCHEMISTRY AND CELL BIOLOGY
2016; 145 (4): 485–96
Phosphoinositides (PIs) are glycerol-based phospholipids containing hydrophilic inositol ring. The inositol ring is mono-, bis-, or tris-phosphorylated yielding seven PIs members. Ample evidence shows that PIs localize both to the cytoplasm and to the nucleus. However, tools for direct visualization of nuclear PIs are limited and many studies thus employ indirect approaches, such as staining of their metabolic enzymes. Since localization and mobility of PIs differ from their metabolic enzymes, these approaches may result in incomplete data. In this paper, we tested commercially available PIs antibodies by light microscopy on fixed cells, tested their specificity using protein-lipid overlay assay and blocking assay, and compared their staining patterns. Additionally, we prepared recombinant PIs-binding domains and tested them on both fixed and live cells by light microscopy. The results provide a useful overview of usability of the tools tested and stress that the selection of adequate tools is critical. Knowing the localization of individual PIs in various functional compartments should enable us to better understand the roles of PIs in the cell nucleus.
View details for DOI 10.1007/s00418-016-1409-8
View details for Web of Science ID 000372608900012
View details for PubMedID 26847181
Paxillin-dependent regulation of IGF2 and H19 gene cluster expression
JOURNAL OF CELL SCIENCE
2015; 128 (16): 3106–16
Paxillin (PXN) is a focal adhesion protein that has been implicated in signal transduction from the extracellular matrix. Recently, it has been shown to shuttle between the cytoplasm and the nucleus. When inside the nucleus, paxillin promotes cell proliferation. Here, we introduce paxillin as a transcriptional regulator of IGF2 and H19 genes. It does not affect the allelic expression of the two genes; rather, it regulates long-range chromosomal interactions between the IGF2 or H19 promoter and a shared distal enhancer on an active allele. Specifically, paxillin stimulates the interaction between the enhancer and the IGF2 promoter, thus activating IGF2 gene transcription, whereas it restrains the interaction between the enhancer and the H19 promoter, downregulating the H19 gene. We found that paxillin interacts with cohesin and the mediator complex, which have been shown to mediate long-range chromosomal looping. We propose that these interactions occur at the IGF2 and H19 gene cluster and are involved in the formation of loops between the IGF2 and H19 promoters and the enhancer, and thus the expression of the corresponding genes. These observations contribute to a mechanistic explanation of the role of paxillin in proliferation and fetal development.
View details for DOI 10.1242/jcs.170985
View details for Web of Science ID 000359783000017
View details for PubMedID 26116569
View details for PubMedCentralID PMC4541046
Nuclear actin filaments recruit cofilin and actin-related protein 3, and their formation is connected with a mitotic block
HISTOCHEMISTRY AND CELL BIOLOGY
2014; 142 (2): 139–52
Although actin monomers polymerize into filaments in the cytoplasm, the form of actin in the nucleus remains elusive. We searched for the form and function of β-actin fused to nuclear localization signal and to enhanced yellow fluorescent protein (EN-actin). Our results reveal that EN-actin is either dispersed in the nucleoplasm (homogenous EN-actin) or forms bundled filaments in the nucleus (EN-actin filaments). Formation of such filaments was not connected with increased EN-actin levels. Among numerous actin-binding proteins tested, only cofilin is recruited to the EN-actin filaments. Overexpression of EN-actin causes increase in the nuclear levels of actin-related protein 3 (Arp3). Although Arp3, a member of actin nucleation complex Arp2/3, is responsible for EN-actin filament nucleation and bundling, the way cofilin affects nuclear EN-actin filaments dynamics is not clear. While cells with homogenous EN-actin maintained unaffected mitosis during which EN-actin re-localizes to the plasma membrane, generation of nuclear EN-actin filaments severely decreases cell proliferation and interferes with mitotic progress. The introduction of EN-actin manifests in two mitotic-inborn defects-formation of binucleic cells and generation of micronuclei-suggesting that cells suffer aberrant cytokinesis and/or impaired chromosomal segregation. In interphase, nuclear EN-actin filaments passed through chromatin region, but do not co-localize with either chromatin remodeling complexes or RNA polymerases I and II. Surprisingly presence of EN-actin filaments was connected with increase in the overall transcription levels in the S-phase by yet unknown mechanism. Taken together, EN-actin can form filaments in the nucleus which affect important cellular processes such as transcription and mitosis.
View details for DOI 10.1007/s00418-014-1243-9
View details for Web of Science ID 000339963300003
View details for PubMedID 25002125
View details for PubMedCentralID PMC4110419