title: Gamma interferon modulates myogenesis through the major histocompatibility complex class II transactivator, CIITA.
abstract: Gamma interferon (IFN-γ) is an inflammatory cytokine that has complex effects on myogenesis. Here, we show that the IFN-γ-induced inhibition of myogenesis is mediated by the major histocompatibility complex (MHC) class II transactivator, CIITA, which binds to myogenin and inhibits its activity. In IFN-γ-treated myoblasts, the inhibition of muscle-specific genes includes the expression of myogenin itself, while in myotubes, myogenin expression is unaffected. Thus, CIITA appears to act by both repressing the expression and inhibiting the activity of myogenin at different stages of myogenesis. Stimulation by IFN-γ in skeletal muscle cells induces CIITA expression as well as MHC class II gene expression. The IFN-γ-mediated repression is reversible, with myogenesis proceeding normally upon removal of IFN-γ. Through overexpression studies, we confirm that the expression of CIITA, independent of IFN-γ, is sufficient to inhibit myogenesis. Through knockdown studies, we also demonstrate that CIITA is necessary for the IFN-γ-mediated inhibition of myogenesis. Finally, we show that CIITA, which lacks DNA binding activity, is recruited to muscle-specific promoters coincident with reductions in RNA polymerase II recruitment. Thus, this work reveals how IFN-γ modulates myogenesis and demonstrates a key role for CIITA in this process.
authors.affiliation: Department of Biochemistry and Molecular Biology, Southern Illinois University School of Medicine, 1245 Lincoln Drive, Carbondale, Illinois 62901, USA.
authors.forename: Priya
authors.initials: P
authors.lastname: Londhe
authors.forename: Judith K
authors.initials: JK
authors.lastname: Davie
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D055785:Gene Knockdown Techniques; D017930:Genes, Reporter; D057809:HEK293 Cells; D006801:Humans; D007371:Interferon-gamma / Q000378:metabolism* / Q000494:pharmacology*; D051379:Mice; D024510:Muscle Development / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000166:cytology / Q000502:physiology; D032446:Myoblasts / Q000166:cytology / Q000502:physiology; D018008:Myogenin / Q000378:metabolism; D041681:NIH 3T3 Cells; D009687:Nuclear Proteins / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism*
chemical_list: C083728:MHC class II transactivator protein; D018008:Myogenin; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D007371:Interferon-gamma