title: G9a promotes proliferation and inhibits cell cycle exit during myogenic differentiation.
abstract: Differentiation of skeletal muscle cells, like most other cell types, requires a permanent exit from the cell cycle. The epigenetic programming underlying these distinct cellular states is not fully understood. In this study, we provide evidence that the lysine methyltransferase G9a functions as a central axis to regulate proliferation and differentiation of skeletal muscle cells. Transcriptome analysis of G9a knockdown cells revealed deregulation of many cell cycle regulatory genes. We demonstrate that G9a enhances cellular proliferation by two distinct mechanisms. G9a blocks cell cycle exit via methylation-dependent transcriptional repression of the MyoD target genes p21(Cip/Waf1) and Rb1. In addition, it activates E2F1-target genes in a methyltransferase activity-independent manner. We show that G9a is present in the E2F1/PCAF complex, and enhances PCAF occupancy and histone acetylation marks at E2F1-target promoters. Interestingly, G9a preferentially associates with E2F1 at the G1/S phase and with MyoD at the G2/M phase. Our results provide evidence that G9a functions both as a co-activator and a co-repressor to enhance cellular proliferation and inhibit myogenic differentiation.
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 117597, Singapore.
authors.forename: Vinay Kumar
authors.initials: VK
authors.lastname: Rao
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 117597, Singapore.
authors.forename: Jin Rong
authors.initials: JR
authors.lastname: Ow
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 117597, Singapore.
authors.forename: Shilpa Rani
authors.initials: SR
authors.lastname: Shankar
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 117597, Singapore.
authors.forename: Narendra
authors.initials: N
authors.lastname: Bharathy
authors.affiliation: NanoString Technologies, 530 Fairview Ave N, Suite 2000 Seattle, WA, USA.
authors.forename: Jayapal
authors.initials: J
authors.lastname: Manikandan
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 117597, Singapore.
authors.forename: Yaju
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, 117597, Singapore phsrt@nus.edu.sg.
authors.forename: Reshma
authors.initials: R
authors.lastname: Taneja
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D002460:Cell Line; D049109:Cell Proliferation / Q000235:genetics; D050687:E2F1 Transcription Factor / Q000378:metabolism; D005786:Gene Expression Regulation; D055785:Gene Knockdown Techniques; D011495:Histone-Lysine N-Methyltransferase / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D008745:Methylation; D008810:Mice, Inbred C57BL; D024510:Muscle Development / Q000235:genetics; D017570:MyoD Protein / Q000378:metabolism; D032446:Myoblasts / Q000166:cytology / Q000378:metabolism; D011401:Promoter Regions, Genetic; D050880:p300-CBP Transcription Factors / Q000378:metabolism; D000099224:p300-CBP-Associated Factor
chemical_list: D050687:E2F1 Transcription Factor; D011495:Histone-Lysine N-Methyltransferase; D006657:Histones; D008239:Lysine; D017570:MyoD Protein; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; C533711:G9a protein, mouse