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Lowe TL, Clarke SG. Human Protein Arginine Methyltransferases (PRMTs) Can Be Optimally Active Under Non-Physiological Conditions. J Biol Chem 2022;:102290. [PMID: 35868559 DOI: 10.1016/j.jbc.2022.102290] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 07/15/2022] [Accepted: 07/16/2022] [Indexed: 11/05/2022] Open
Abstract
Protein arginine methylation is involved in many biological processes and can be enhanced in cancer. In mammals, these reactions are catalyzed on multiple substrates by a family of nine protein arginine methyltransferases (PRMTs). However, conditions that may regulate the activity of each enzyme and that may help us understand the physiological role of PRMTs have not been fully established. Previous studies had suggested unexpected effects of temperature and ionic strength on PRMT7 activity. Here we examine in detail the effects of temperature, pH, and ionic strength on recombinant human PRMT1, PRMT5, and PRMT7. We confirmed the unusual temperature dependence of PRMT7, where optimal activity was observed at 15 °C. On the other hand, we found that PRMT1 and PRMT5 are most active near physiological temperatures of 37 °C. However, we showed all three enzymes still have significant activity at 0 °C. Furthermore, we determined that PRMT1 is most active at a pH of about 7.7, while PRMT5 activity is not dependent on pH in the range of 6.5 to 8.5. Significantly, PRMT7 is most active at an alkaline pH of 8.5 but shows little activity at the physiological intracellular pH of about 7.2. We also detected decreased activity at physiological salt conditions for PRMT1, PRMT5, and PRMT7. We demonstrate that the loss of activity is due to the increasing ionic strength. Taken together, these results open the possibility that PRMTs respond in cells undergoing temperature, salt, or pH stress and demonstrate the potential for in vivo regulation of protein arginine methylation.
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Chung J, Karkhanis V, Baiocchi RA, Sif S. Protein arginine methyltransferase 5 (PRMT5) promotes survival of lymphoma cells via activation of WNT/β-catenin and AKT/GSK3β proliferative signaling. J Biol Chem 2019; 294:7692-7710. [PMID: 30885941 DOI: 10.1074/jbc.ra119.007640] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 03/04/2019] [Indexed: 02/02/2023] Open
Abstract
Epigenetic regulation by the type II protein arginine methyltransferase, PRMT5, plays an essential role in the control of cancer cell proliferation and tumorigenesis. In this report, we investigate the relationship between PRMT5 and WNT/β-CATENIN as well as AKT/GSK3β proliferative signaling in three different types of non-Hodgkin's lymphoma cell lines, clinical samples, and mouse primary lymphoma cells. We show that PRMT5 stimulates WNT/β-CATENIN signaling through direct epigenetic silencing of pathway antagonists, AXIN2 and WIF1, and indirect activation of AKT/GSK3β signaling. PRMT5 inhibition with either shRNA-mediated knockdown or a specific small molecule PRMT5 inhibitor, CMP-5, not only leads to derepression of WNT antagonists and decreased levels of active phospho-AKT (Thr-450 and Ser-473) and inactive phospho-GSK3β (Ser-9) but also results in decreased transcription of WNT/β-CATENIN target genes, CYCLIN D1, c-MYC, and SURVIVIN, and enhanced lymphoma cell death. Furthermore, PRMT5 inhibition leads to reduced recruitment of co-activators CBP, p300, and MLL1, as well as enhanced recruitment of co-repressors HDAC2 and LSD1 to the WNT/β-CATENIN target gene promoters. These results indicate that PRMT5 governs expression of prosurvival genes by promoting WNT/β-CATENIN and AKT/GSK3β proliferative signaling and that its inhibition induces lymphoma cell death, which warrants further clinical evaluation.
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Affiliation(s)
- Jihyun Chung
- From the Division of Hematology, Department of Internal Medicine, the Ohio State University, Columbus, Ohio 43210 and
| | - Vrajesh Karkhanis
- From the Division of Hematology, Department of Internal Medicine, the Ohio State University, Columbus, Ohio 43210 and
| | - Robert A Baiocchi
- From the Division of Hematology, Department of Internal Medicine, the Ohio State University, Columbus, Ohio 43210 and
| | - Saïd Sif
- the Department of Biological and Environmental Sciences, College of Arts and Sciences, Qatar University, Doha, Qatar
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Nie M, Wang Y, Guo C, Li X, Wang Y, Deng Y, Yao B, Gui T, Ma C, Liu M, Wang P, Wang R, Tan R, Fang M, Chen B, He Y, Huang DCS, Ju J, Zhao Q. CARM1-mediated methylation of protein arginine methyltransferase 5 represses human γ-globin gene expression in erythroleukemia cells. J Biol Chem 2018; 293:17454-17463. [PMID: 30257864 DOI: 10.1074/jbc.ra118.004028] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 09/10/2018] [Indexed: 12/22/2022] Open
Abstract
Protein arginine methyltransferase 5 (PRMT5) is a member of the arginine methyltransferase protein family that critically mediates the symmetric dimethylation of Arg-3 at histone H4 (H4R3me2s) and is involved in many key cellular processes, including hematopoiesis. However, the post-translational modifications (PTMs) of PRMT5 that may affect its biological functions remain less well-understood. In this study, using MS analyses, we found that PRMT5 itself is methylated in human erythroleukemia Lys-562 cells. Biochemical assays revealed that coactivator-associated arginine methyltransferase 1 (CARM1) interacts directly with and methylates PRMT5 at Arg-505 both in vivo and in vitro. Substitutions at Arg-505 significantly reduced PRMT5's methyltransferase activity, decreased H4R3me2s enrichment at the γ-globin gene promoter, and increased the expression of the γ-globin gene in Lys-562 cells. Moreover, CARM1 knockdown consistently reduced PRMT5 activity and activated γ-globin gene expression. Importantly, we show that CARM1-mediated methylation of PRMT5 is essential for the intracellular homodimerization of PRMT5 to its active form. These results thus reveal a critical PTM of PRMT5 that represses human γ-globin gene expression. We conclude that CARM1-mediated asymmetric methylation of PRMT5 is critical for its dimerization and methyltransferase activity leading to the repression of γ-globin expression. Given PRMT5's crucial role in diverse cellular processes, these findings may inform strategies for manipulating its methyltransferase activity for managing hemoglobinopathy or cancer.
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Affiliation(s)
- Min Nie
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Yadong Wang
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Chan Guo
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Xinyu Li
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Ying Wang
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Yexuan Deng
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Bing Yao
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Tao Gui
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Chi Ma
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Ming Liu
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Panxue Wang
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Ruoyun Wang
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Renxiang Tan
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China.,State Key Laboratory Cultivation Base for TCM Quality and Efficacy, Nanjing University of Chinese Medicine, Nanjing 210046, China
| | - Ming Fang
- Institute of Life Sciences, Southeast University, Nanjing 210096, China
| | - Bing Chen
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China
| | - Yinghong He
- School of Basic Medicine, Dali University, Yunnan 671003 China, and
| | - David C S Huang
- Department of Medical Biology, The Walter and Eliza Hall Institute of Medical Research, University of Melbourne, Melbourne, Victoria, 3010 Australia
| | - Junyi Ju
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China,
| | - Quan Zhao
- From the State Key Laboratory of Pharmaceutical Biotechnology, Department of Hematology, the Affiliated Drum Tower Hospital of Nanjing University Medical School, China-Australia Center for Translational Medicine, School of Life Sciences, Nanjing University, Nanjing 210023, China,
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Espejo AB, Gao G, Black K, Gayatri S, Veland N, Kim J, Chen T, Sudol M, Walker C, Bedford MT. PRMT5 C-terminal Phosphorylation Modulates a 14-3-3/PDZ Interaction Switch. J Biol Chem 2016; 292:2255-2265. [PMID: 28031468 PMCID: PMC5313098 DOI: 10.1074/jbc.m116.760330] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2016] [Revised: 12/21/2016] [Indexed: 11/06/2022] Open
Abstract
PRMT5 is the primary enzyme responsible for the deposition of the symmetric dimethylarginine in mammalian cells. In an effort to understand how PRMT5 is regulated, we identified a threonine phosphorylation site within a C-terminal tail motif, which is targeted by the Akt/serum- and glucocorticoid-inducible kinases. While investigating the function of this posttranslational modification, we serendipitously discovered that its free C-terminal tail binds PDZ domains (when unphosphorylated) and 14-3-3 proteins (when phosphorylated). In essence, a phosphorylation event within the last few residues of the C-terminal tail generates a posttranslational modification-dependent PDZ/14-3-3 interaction "switch." The C-terminal motif of PRMT5 is required for plasma membrane association, and loss of this switching capacity is not compatible with life. This signaling phenomenon was recently reported for the HPV E6 oncoprotein but has not yet been observed for mammalian proteins. To investigate the prevalence of PDZ/14-3-3 switching in signal transduction, we built a protein domain microarray that harbors PDZ domains and 14-3-3 proteins. We have used this microarray to interrogate the C-terminal tails of a small group of candidate proteins and identified ERBB4, PGHS2, and IRK1 (as well as E6 and PRMT5) as conforming to this signaling mode, suggesting that PDZ/14-3-3 switching may be a broad biological paradigm.
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Affiliation(s)
- Alexsandra B Espejo
- From the Department of Epigenetics and Molecular Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Smithville, Texas 78957.,the University of Texas Graduate School of Biomedical Sciences, Houston, Texas 77030
| | - Guozhen Gao
- From the Department of Epigenetics and Molecular Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Smithville, Texas 78957
| | - Karynne Black
- From the Department of Epigenetics and Molecular Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Smithville, Texas 78957
| | - Sitaram Gayatri
- From the Department of Epigenetics and Molecular Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Smithville, Texas 78957.,the University of Texas Graduate School of Biomedical Sciences, Houston, Texas 77030
| | - Nicolas Veland
- From the Department of Epigenetics and Molecular Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Smithville, Texas 78957.,the University of Texas Graduate School of Biomedical Sciences, Houston, Texas 77030
| | - Jeesun Kim
- From the Department of Epigenetics and Molecular Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Smithville, Texas 78957
| | - Taiping Chen
- From the Department of Epigenetics and Molecular Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Smithville, Texas 78957
| | - Marius Sudol
- the Department of Physiology, National University of Singapore, Mechanobiology Institute and Institute for Molecular and Cell Biology (IMCB, A*STAR), Singapore 117597, Singapore, and
| | - Cheryl Walker
- the Institute of Biosciences and Technology, Texas A&M Health Science Center, Houston, Texas 77030
| | - Mark T Bedford
- From the Department of Epigenetics and Molecular Carcinogenesis, University of Texas M.D. Anderson Cancer Center, Smithville, Texas 78957,
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Tsai WC, Gayatri S, Reineke LC, Sbardella G, Bedford MT, Lloyd RE. Arginine Demethylation of G3BP1 Promotes Stress Granule Assembly. J Biol Chem 2016; 291:22671-22685. [PMID: 27601476 DOI: 10.1074/jbc.m116.739573] [Citation(s) in RCA: 133] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2016] [Revised: 08/15/2016] [Indexed: 12/22/2022] Open
Abstract
Stress granules (SGs) are cytoplasmic condensates of stalled messenger ribonucleoprotein complexes (mRNPs) that form when eukaryotic cells encounter environmental stress. RNA-binding proteins are enriched for arginine methylation and facilitate SG assembly through interactions involving regions of low amino acid complexity. How methylation of specific RNA-binding proteins regulates RNA granule assembly has not been characterized. Here, we examined the potent SG-nucleating protein Ras-GAP SH3-binding protein 1 (G3BP1), and found that G3BP1 is differentially methylated on specific arginine residues by protein arginine methyltransferase (PRMT) 1 and PRMT5 in its RGG domain. Several genetic and biochemical interventions that increased methylation repressed SG assembly, whereas interventions that decreased methylation promoted SG assembly. Arsenite stress quickly and reversibly decreased asymmetric arginine methylation on G3BP1. These data indicate that arginine methylation in the RGG domain prevents large SG assembly and rapid demethylation is a novel signal that regulates SG formation.
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Affiliation(s)
- Wei-Chih Tsai
- From the Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030
| | - Sitaram Gayatri
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas M. D. Anderson Cancer Center, Science Park, Smithville, Texas 78957, and
| | - Lucas C Reineke
- From the Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030
| | - Gianluca Sbardella
- Epigenetic Med Chem Lab, Dipartimento di Farmacia, Università degli Studi di Salerno, Via Giovanni Paolo II 132, I-84084 Fisciano, Salerno, Italy
| | - Mark T Bedford
- Department of Epigenetics and Molecular Carcinogenesis, University of Texas M. D. Anderson Cancer Center, Science Park, Smithville, Texas 78957, and
| | - Richard E Lloyd
- From the Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas 77030,
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Wu TF, Yao YL, Lai IL, Lai CC, Lin PL, Yang WM. Loading of PAX3 to Mitotic Chromosomes Is Mediated by Arginine Methylation and Associated with Waardenburg Syndrome. J Biol Chem 2015; 290:20556-64. [PMID: 26149688 DOI: 10.1074/jbc.m114.607713] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2014] [Indexed: 11/06/2022] Open
Abstract
PAX3 is a transcription factor critical to gene regulation in mammalian development. Mutations in PAX3 are associated with Waardenburg syndrome (WS), but the mechanism of how mutant PAX3 proteins cause WS remains unclear. Here, we found that PAX3 loads on mitotic chromosomes using its homeodomain. PAX3 WS mutants with mutations in homeodomain lose the ability to bind mitotic chromosomes. Moreover, loading of PAX3 on mitotic chromosomes requires arginine methylation, which is regulated by methyltransferase PRMT5 and demethylase JMJD6. Mutant PAX3 proteins that lose mitotic chromosome localization block cell proliferation and normal development of zebrafish. These results reveal the molecular mechanism of PAX3s loading on mitotic chromosomes and the importance of this localization pattern in normal development. Our findings suggest that PAX3 WS mutants interfere with the normal functions of PAX3 in a dominant negative manner, which is important to the understanding of the pathogenesis of Waardenburg syndrome.
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Affiliation(s)
- Tsu-Fang Wu
- From the Department of Life Sciences, Department of Biotechnology, Hung Kuang University, Taichung 43302, Taiwan
| | - Ya-Li Yao
- Department of Biotechnology, Asia University, Taichung 41354, Taiwan, and
| | - I-Lu Lai
- the Institute of Molecular Biology, and
| | | | - Pei-Lun Lin
- Bachelor Program of Biotechnology, National Chung Hsing University, Taichung 40227, Taiwan
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7
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Hadjikyriacou A, Yang Y, Espejo A, Bedford MT, Clarke SG. Unique Features of Human Protein Arginine Methyltransferase 9 (PRMT9) and Its Substrate RNA Splicing Factor SF3B2. J Biol Chem 2015; 290:16723-43. [PMID: 25979344 DOI: 10.1074/jbc.m115.659433] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Indexed: 12/29/2022] Open
Abstract
Human protein arginine methyltransferase (PRMT) 9 symmetrically dimethylates arginine residues on splicing factor SF3B2 (SAP145) and has been functionally linked to the regulation of alternative splicing of pre-mRNA. Site-directed mutagenesis studies on this enzyme and its substrate had revealed essential unique residues in the double E loop and the importance of the C-terminal duplicated methyltransferase domain. In contrast to what had been observed with other PRMTs and their physiological substrates, a peptide containing the methylatable Arg-508 of SF3B2 was not recognized by PRMT9 in vitro. Although amino acid substitutions of residues surrounding Arg-508 had no great effect on PRMT9 recognition of SF3B2, moving the arginine residue within this sequence abolished methylation. PRMT9 and PRMT5 are the only known mammalian enzymes capable of forming symmetric dimethylarginine (SDMA) residues as type II PRMTs. We demonstrate here that the specificity of these enzymes for their substrates is distinct and not redundant. The loss of PRMT5 activity in mouse embryo fibroblasts results in almost complete loss of SDMA, suggesting that PRMT5 is the primary SDMA-forming enzyme in these cells. PRMT9, with its duplicated methyltransferase domain and conserved sequence in the double E loop, appears to have a unique structure and specificity among PRMTs for methylating SF3B2 and potentially other polypeptides.
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Affiliation(s)
- Andrea Hadjikyriacou
- From the Department of Chemistry and Biochemistry and the Molecular Biology Institute, UCLA, Los, Angeles, California 90095 and
| | - Yanzhong Yang
- the Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, Texas 78957
| | - Alexsandra Espejo
- the Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, Texas 78957
| | - Mark T Bedford
- the Department of Epigenetics and Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, Texas 78957
| | - Steven G Clarke
- From the Department of Chemistry and Biochemistry and the Molecular Biology Institute, UCLA, Los, Angeles, California 90095 and
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Saha K, Eckert RL. Methylosome Protein 50 and PKCδ/p38δ Protein Signaling Control Keratinocyte Proliferation via Opposing Effects on p21Cip1 Gene Expression. J Biol Chem 2015; 290:13521-30. [PMID: 25851901 DOI: 10.1074/jbc.m115.642868] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Indexed: 11/06/2022] Open
Abstract
Protein arginine methyltransferase 5 (PRMT5) is a key epigenetic regulator that symmetrically dimethylates arginine residues on histones H3 and H4 to silence gene expression. PRMT5 is frequently observed in a complex with the cofactor methylosome protein 50 (MEP50), which is required for PRMT5 activity. PKCδ/p38δ signaling, a key controller of keratinocyte proliferation and differentiation, increases p21(Cip1) expression to suppress keratinocyte proliferation. We now show that MEP50 enhances keratinocyte proliferation and survival via mechanisms that include silencing of p21(Cip1) expression. This is associated with enhanced PRMT5-MEP50 interaction at the p21(Cip1) promoter and enhanced arginine dimethylation of the promoter-associated histones H3 and H4. It is also associated with a MEP50-dependent reduction in the level of p53, a key controller of p21(Cip1) gene expression. We confirm an important biological role for MEP50 and PRMT5 in regulating keratinocyte proliferation using a stratified epidermal equivalent model that mimics in vivo epidermal keratinocyte differentiation. In this model, PRMT5 or MEP50 knockdown results in reduced keratinocyte proliferation. We further show that PKCδ/p38δ signaling suppresses MEP50 expression, leading to reduced H3/H4 arginine dimethylation at the p21(Cip1) promoter, and that this is associated with enhanced p21(Cip1) expression and reduced cell proliferation. These findings describe an opposing action between PKCδ/p38δ MAPK signaling and PRMT5/MEP50 epigenetic silencing mechanisms in regulating cell proliferation.
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Affiliation(s)
- Kamalika Saha
- From the Departments of Biochemistry and Molecular Biology
| | - Richard L Eckert
- From the Departments of Biochemistry and Molecular Biology, Dermatology, and Obstetrics and Gynecology and the Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, Maryland 21201
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