Hyunje Kang

All Publications

• Macrophage transcription factor TonEBP promotes systemic lupus erythematosus and kidney injury via damage-induced signaling pathways. Kidney international Yoo, E. J., Oh, K. H., Piao, H., Kang, H. J., Jeong, G. W., Park, H., Lee, C. J., Ryu, H., Yang, S. H., Kim, M. G., Kim, D. K., Park, S. H., Lim, B. J., Lee, S. M., Park, C. Y., Choi, S. Y., Lee-Kwon, W., Yang, J., Kwon, H. M. 2023; 104 (1): 163-180

  Abstract

  Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by autoreactive B cells and dysregulation of many other types of immune cells including myeloid cells. Lupus nephritis (LN) is a common target organ manifestations of SLE. Tonicity-responsive enhancer-binding protein (TonEBP, also known as nuclear factor of activated T-cells 5 (NFAT5)), was initially identified as a central regulator of cellular responses to hypertonic stress and is a pleiotropic stress protein involved in a variety of immunometabolic diseases. To explore the role of TonEBP, we examined kidney biopsy samples from patients with LN. Kidney TonEBP expression was found to be elevated in these patients compared to control patients - in both kidney cells and infiltrating immune cells. Kidney TonEBP mRNA was elevated in LN and correlated with mRNAs encoding inflammatory cytokines and the degree of proteinuria. In a pristane-induced SLE model in mice, myeloid TonEBP deficiency blocked the development of SLE and LN. In macrophages, engagement of various toll-like receptors (TLRs) that respond to damage-associated molecular patterns induced TonEBP expression via stimulation of its promoter. Intracellular signaling downstream of the TLRs was dependent on TonEBP. Therefore, TonEBP can act as a transcriptional cofactor for NF-κB, and activated mTOR-IRF3/7 via protein-protein interactions. Additionally, TonEBP-deficient macrophages displayed elevated efferocytosis and animals with myeloid deficiency of TonEBP showed reduced Th1 and Th17 differentiation, consistent with macrophages defective in TLR signaling. Thus, our data show that myeloid TonEBP may be an attractive therapeutic target for SLE and LN.

  View details for DOI 10.1016/j.kint.2023.03.030

  View details for PubMedID 37088425

• Thrap3 promotes R-loop resolution via interaction with methylated DDX5. Experimental & molecular medicine Kang, H. J., Eom, H. J., Kim, H., Myung, K., Kwon, H. M., Choi, J. H. 2021; 53 (10): 1602-1611

  Abstract

  Transcription-replication conflicts lead to DNA damage and genomic instability, which are closely related to human diseases. A major source of these conflicts is the formation of R-loops, which consist of an RNA-DNA hybrid and a displaced single-stranded DNA. Although these structures have been studied, many aspects of R-loop biology and R-loop-mediated genome instability remain unclear. Here, we demonstrate that thyroid hormone receptor-associated protein 3 (Thrap3) plays a critical role in regulating R-loop resolution. In cancer cells, Thrap3 interacts with DEAD-box helicase 5 (DDX5) and localizes to R-loops. Arginine-mediated methylation of DDX5 is required for its interaction with Thrap3, and the Thrap3-DDX5 axis induces the recruitment of 5'-3' exoribonuclease 2 (XRN2) into R-loops. Loss of Thrap3 increases R-loop accumulation and DNA damage. These findings suggest that Thrap3 mediates resistance to cell death by preventing R-loop accumulation in cancer cells.

  View details for DOI 10.1038/s12276-021-00689-6

  View details for PubMedID 34697388

  View details for PubMedCentralID PMC8569202

• PARP1-mediated PARylation of TonEBP prevents R-loop-associated DNA damage. DNA repair Ye, B. J., Kang, H. J., Lee-Kwon, W., Kwon, H. M., Choi, S. Y. 2021; 104: 103132

  Abstract

  Lack of coordination between the DNA replication and transcription machineries can increase the frequency of transcription-replication conflicts, leading ultimately to DNA damage and genomic instability. A major source of these conflicts is the formation of R-loops, which consist of a transcriptionally generated RNA-DNA hybrid and the displaced single-stranded DNA. R-loops play important physiological roles and have been implicated in human diseases. Although these structures have been extensively studied, many aspects of R-loop biology and R-loop-mediated genome instability remain unclear. We found that in cancer cells, tonicity-responsive enhancer-binding protein (TonEBP, also called NFAT5) interacted with PARP1 and localized to R-loops in response to DNA-damaging agent camptothecin (CPT), which is associated with R-loop formation. PARP1-mediated PARylation was required for recruitment of TonEBP to the sites of R-loop-associated DNA damage. Loss of TonEBP increased levels of R-loop accumulation and DNA damage, and promoted cell death in response to CPT. These findings suggest that TonEBP mediates resistance to CPT-induced cell death by preventing R-loop accumulation in cancer cells.

  View details for DOI 10.1016/j.dnarep.2021.103132

  View details for PubMedID 34049076

• TonEBP recognizes R-loops and initiates m6A RNA methylation for R-loop resolution. Nucleic acids research Kang, H. J., Cheon, N. Y., Park, H., Jeong, G. W., Ye, B. J., Yoo, E. J., Lee, J. H., Hur, J. H., Lee, E. A., Kim, H., Lee, K. Y., Choi, S. Y., Lee-Kwon, W., Myung, K., Lee, J. Y., Kwon, H. M. 2021; 49 (1): 269-284

  Abstract

  R-loops are three-stranded, RNA-DNA hybrid, nucleic acid structures produced due to inappropriate processing of newly transcribed RNA or transcription-replication collision (TRC). Although R-loops are important for many cellular processes, their accumulation causes genomic instability and malignant diseases, so these structures are tightly regulated. It was recently reported that R-loop accumulation is resolved by methyltransferase-like 3 (METTL3)-mediated m6A RNA methylation under physiological conditions. However, it remains unclear how R-loops in the genome are recognized and induce resolution signals. Here, we demonstrate that tonicity-responsive enhancer binding protein (TonEBP) recognizes R-loops generated by DNA damaging agents such as ultraviolet (UV) or camptothecin (CPT). Single-molecule imaging and biochemical assays reveal that TonEBP preferentially binds a R-loop via both 3D collision and 1D diffusion along DNA in vitro. In addition, we find that TonEBP recruits METTL3 to R-loops through the Rel homology domain (RHD) for m6A RNA methylation. We also show that TonEBP recruits RNaseH1 to R-loops through a METTL3 interaction. Consistent with this, TonEBP or METTL3 depletion increases R-loops and reduces cell survival in the presence of UV or CPT. Collectively, our results reveal an R-loop resolution pathway by TonEBP and m6A RNA methylation by METTL3 and provide new insights into R-loop resolution processes.

  View details for DOI 10.1093/nar/gkaa1162

  View details for PubMedID 33313823

  View details for PubMedCentralID PMC7797050

• TonEBP Promotes β-Cell Survival under ER Stress by Enhancing Autophagy. Cells Kang, H. J., Yoo, E. J., Lee, H. H., An, S. M., Park, H., Lee-Kwon, W., Choi, S. Y., Kwon, H. M. 2020; 9 (9)

  Abstract

  The endoplasmic reticulum (ER) stress response and autophagy are important cellular responses that determine cell fate and whose dysregulation is implicated in the perturbation of homeostasis and diseases. Tonicity-responsive enhancer-binding protein (TonEBP, also called NFAT5) is a pleiotropic stress protein that mediates both protective and pathological cellular responses. Here, we examined the role of TonEBP in β-cell survival under ER stress. We found that TonEBP increases β-cell survival under ER stress by enhancing autophagy. The level of TonEBP protein increased under ER stress due to a reduction in its degradation via the ubiquitin-proteasome pathway. In response to ER stress, TonEBP increased autophagosome formations and suppressed the accumulation of protein aggregates and β-cell death. The Rel-homology domain of TonEBP interacted with FIP200, which is essential for the initiation of autophagy, and was required for autophagy and cell survival upon exposure to ER stress. Mice in which TonEBP was specifically deleted in pancreatic endocrine progenitor cells exhibited defective glucose homeostasis and a loss of islet mass. Taken together, these findings demonstrate that TonEBP protects against ER stress-induced β-cell death by enhancing autophagy.

  View details for DOI 10.3390/cells9091928

  View details for PubMedID 32825390

  View details for PubMedCentralID PMC7563687

• TonEBP in dendritic cells mediates pro-inflammatory maturation and Th1/Th17 responses. Cell death & disease Ye, B. J., Lee, H. H., Yoo, E. J., Lee, C. Y., Lee, J. H., Kang, H. J., Jeong, G. W., Park, H., Lee-Kwon, W., Choi, S. Y., Kwon, H. M. 2020; 11 (6): 421

  Abstract

  Dendritic cells (DCs) are potent antigen-presenting cells that link the innate and adaptive immune responses; as such they play pivotal roles in initiation and progression of rheumatoid arthritis (RA). Here, we report that the tonicity-responsive enhancer-binding protein (TonEBP or NFAT5), a Rel family protein involved in the pathogenesis of autoimmune disease and inflammation, is required for maturation and function of DCs. Myeloid cell-specific TonEBP deletion reduces disease severity in a murine model of collagen-induced arthritis; it also inhibits maturation of DCs and differentiation of pathogenic Th1 and Th17 cells in vivo. Upon stimulation by TLR4, TonEBP promotes surface expression of major histocompatibility complex class II and co-stimulatory molecules via p38 mitogen-activated protein kinase. This is followed by DC-mediated differentiation of pro-inflammatory Th1 and Th17 cells. Taken together, these findings provide mechanistic basis for the pathogenic role of TonEBP in RA and possibly other autoimmune diseases.

  View details for DOI 10.1038/s41419-020-2632-8

  View details for PubMedID 32499518

  View details for PubMedCentralID PMC7272407

• Transcriptional Regulator TonEBP Mediates Oxidative Damages in Ischemic Kidney Injury. Cells Yoo, E. J., Lim, S. W., Kang, H. J., Park, H., Yoon, S., Nam, D., Sanada, S., Kwon, M. J., Lee-Kwon, W., Choi, S. Y., Kwon, H. M. 2019; 8 (10)

  Abstract

  TonEBP (tonicity-responsive enhancer binding protein) is a transcriptional regulator whose expression is elevated in response to various forms of stress including hyperglycemia, inflammation, and hypoxia. Here we investigated the role of TonEBP in acute kidney injury (AKI) using a line of TonEBP haplo-deficient mice subjected to bilateral renal ischemia followed by reperfusion (I/R). In the TonEBP haplo-deficient animals, induction of TonEBP, oxidative stress, inflammation, cell death, and functional injury in the kidney in response to I/R were all reduced. Analyses of renal transcriptome revealed that genes in several cellular pathways including peroxisome and mitochondrial inner membrane were suppressed in response to I/R, and the suppression was relieved in the TonEBP deficiency. Production of reactive oxygen species (ROS) and the cellular injury was reproduced in a renal epithelial cell line in response to hypoxia, ATP depletion, or hydrogen peroxide. The knockdown of TonEBP reduced ROS production and cellular injury in correlation with increased expression of the suppressed genes. The cellular injury was also blocked by inhibitors of necrosis. These results demonstrate that ischemic insult suppresses many genes involved in cellular metabolism leading to local oxidative stress by way of TonEBP induction. Thus, TonEBP is a promising target to prevent AKI.

  View details for DOI 10.3390/cells8101284

  View details for PubMedID 31635160

  View details for PubMedCentralID PMC6830075

• TonEBP Regulates PCNA Polyubiquitination in Response to DNA Damage through Interaction with SHPRH and USP1. iScience Kang, H. J., Park, H., Yoo, E. J., Lee, J. H., Choi, S. Y., Lee-Kwon, W., Lee, K. Y., Hur, J. H., Seo, J. K., Ra, J. S., Lee, E. A., Myung, K., Kwon, H. M. 2019; 19: 177-190

  Abstract

  Polyubiquitination of proliferating cell nuclear antigen (PCNA) regulates the error-free template-switching mechanism for the bypass of DNA lesions during DNA replication. PCNA polyubiquitination is critical for the maintenance of genomic integrity; however, the underlying mechanism is poorly understood. Here, we demonstrate that tonicity-responsive enhancer-binding protein (TonEBP) regulates PCNA polyubiquitination in response to DNA damage. TonEBP was recruited to DNA damage sites with bulky adducts and sequentially recruited E3 ubiquitin ligase SHPRH, followed by deubiquitinase USP1, to DNA damage sites, in correlation with the dynamics of PCNA polyubiquitination. Similarly, TonEBP was found to be required for replication fork protection in response to DNA damage. The Rel-homology domain of TonEBP, which encircles DNA, was essential for the interaction with SHPRH and USP1, PCNA polyubiquitination, and cell survival after DNA damage. The present findings suggest that TonEBP is an upstream regulator of PCNA polyubiquitination and of the DNA damage bypass pathway.

  View details for DOI 10.1016/j.isci.2019.07.021

  View details for PubMedID 31376680

  View details for PubMedCentralID PMC6677787

• TonEBP/NFAT5 promotes obesity and insulin resistance by epigenetic suppression of white adipose tissue beiging. Nature communications Lee, H. H., An, S. M., Ye, B. J., Lee, J. H., Yoo, E. J., Jeong, G. W., Kang, H. J., Alfadda, A. A., Lim, S. W., Park, J., Lee-Kwon, W., Kim, J. B., Choi, S. Y., Kwon, H. M. 2019; 10 (1): 3536

  Abstract

  Tonicity-responsive enhancer binding protein (TonEBP or NFAT5) is a regulator of cellular adaptation to hypertonicity, macrophage activation and T-cell development. Here we report that TonEBP is an epigenetic regulator of thermogenesis and obesity. In mouse subcutaneous adipocytes, TonEBP expression increases > 50-fold in response to high-fat diet (HFD) feeding. Mice with TonEBP haplo-deficiency or adipocyte-specific TonEBP deficiency are resistant to HFD-induced obesity and metabolic defects (hyperglycemia, hyperlipidemia, and hyperinsulinemia). They also display increased oxygen consumption, resistance to hypothermia, and beiging of subcutaneous fat tissues. TonEBP suppresses the promoter of β3-adrenoreceptor gene, a critical regulator of lipolysis and thermogenesis, in ex vivo and cultured adipocytes. This involves recruitment of DNMT1 DNA methylase and methylation of the promoter. In human subcutaneous adipocytes TonEBP expression displays a correlation with body mass index but an inverse correlation with β3-adrenoreceptor expression. Thus, TonEBP is an attractive therapeutic target for obesity, insulin resistance, and hyperlipidemia.

  View details for DOI 10.1038/s41467-019-11302-w

  View details for PubMedID 31387996

  View details for PubMedCentralID PMC6684655

• TonEBP promotes chemoresistance and recurrence of hepatocellular carcinoma via DNA repair of cancer stem cells Lee, J., Suh, J., Choi, S., Kang, H., Scharer, O. D., Park, N., Kwon, H. AMER ASSOC CANCER RESEARCH. 2019

  View details for DOI 10.1158/1538-7445.SABCS18-3694

  View details for Web of Science ID 000488279403098

• TonEBP Suppresses the HO-1 Gene by Blocking Recruitment of Nrf2 to Its Promoter. Frontiers in immunology Yoo, E. J., Lee, H. H., Ye, B. J., Lee, J. H., Lee, C. Y., Kang, H. J., Jeong, G. W., Park, H., Lim, S. W., Lee-Kwon, W., Kwon, H. M., Choi, S. Y. 2019; 10: 850

  Abstract

  TonEBP is a key transcriptional activator in macrophages with an M1 phenotype. High expression of TonEBP is associated with many inflammatory diseases. Heme oxygenase-1 (HO-1), a stress-inducible protein, is induced by various oxidative and inflammatory signals, and its expression is regarded as an adaptive cellular response to inflammation and oxidative injury. Here, we show that TonEBP suppresses expression of HO-1 by blocking Nrf2 binding to the HO-1 promoter, thereby inducing polarization of macrophages to the M1 phenotype. Inhibition of HO-1 expression or activity significantly reduced the inhibitory responses on M1 phenotype and stimulatory effects on M2 phenotype by TonEBP knockdown. Additional experiments showed that HO-1 plays a role in the paracrine anti-inflammatory effects of TonEBP knockdown in macrophages. Identification of HO-1 as a downstream effector of TonEBP provides new possibilities for improved therapeutic approaches to inflammatory diseases.

  View details for DOI 10.3389/fimmu.2019.00850

  View details for PubMedID 31057560

  View details for PubMedCentralID PMC6482272