title: Stress-induced C/EBP homology protein (CHOP) represses MyoD transcription to delay myoblast differentiation.
abstract: When mouse myoblasts or satellite cells differentiate in culture, the expression of myogenic regulatory factor, MyoD, is downregulated in a subset of cells that do not differentiate. The mechanism involved in the repression of MyoD expression remains largely unknown. Here we report that a stress-response pathway repressing MyoD transcription is transiently activated in mouse-derived C2C12 myoblasts growing under differentiation-promoting conditions. We show that phosphorylation of the α subunit of the translation initiation factor 2 (eIF2α) is followed by expression of C/EBP homology protein (CHOP) in some myoblasts. ShRNA-driven knockdown of CHOP expression caused earlier and more robust differentiation, whereas its constitutive expression delayed differentiation relative to wild type myoblasts. Cells expressing CHOP did not express the myogenic regulatory factors MyoD and myogenin. These results indicated that CHOP directly repressed the transcription of the MyoD gene. In support of this view, CHOP associated with upstream regulatory region of the MyoD gene and its activity reduced histone acetylation at the enhancer region of MyoD. CHOP interacted with histone deacetylase 1 (HDAC1) in cells. This protein complex may reduce histone acetylation when bound to MyoD regulatory regions. Overall, our results suggest that the activation of a stress pathway in myoblasts transiently downregulate the myogenic program.
authors.affiliation: Department of Biochemistry, Rappaport Institute for Research in the Medical Sciences, Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel.
authors.forename: Joel
authors.initials: J
authors.lastname: Alter
authors.forename: Eyal
authors.initials: E
authors.lastname: Bengal
mesh_terms: D000107:Acetylation; D051700:Activating Transcription Factor 3 / Q000378:metabolism; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics*; D002460:Cell Line; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D005786:Gene Expression Regulation; D006657:Histones / Q000378:metabolism; D051379:Mice; D024510:Muscle Development / Q000235:genetics; D017570:MyoD Protein / Q000235:genetics* / Q000378:metabolism; D032446:Myoblasts / Q000166:cytology* / Q000378:metabolism; D018008:Myogenin / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding / Q000235:genetics; D012097:Repressor Proteins / Q000378:metabolism*; D013312:Stress, Physiological; D051742:Transcription Factor CHOP / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D051700:Activating Transcription Factor 3; C103002:Atf3 protein, mouse; D015415:Biomarkers; D015852:Eukaryotic Initiation Factor-2; D006657:Histones; D017570:MyoD Protein; D018008:Myogenin; D012097:Repressor Proteins; D051742:Transcription Factor CHOP