TGFbeta1 regulation of vimentin gene expression during differentiation of the C2C12 skeletal myogenic cell line requires Smads, AP-1 and Sp1 family members.
Vimentin exhibits a complex pattern of developmental and tissue-specific expression regulated by such growth factors as TGFbeta1, PDGF, FGF, EGF and cytokines. Vimentin is expressed in the more migratory, mesenchymal cell and its expression is often down-regulated to make way for tissue-specific intermediate filaments proteins such as desmin in muscle. Here, we suggest a mechanism to explain how TGFbeta1 contributes to the up-regulation of vimentin expression while blocking myogenesis. TGFbeta1 binds to serine/threonine kinase receptors resulting in the phosphorylation of Smad2 and Smad3, followed by formation of a heteromeric complex with Smad4. The translocation of this complex to the nucleus modulates transcription of selected genes such as vimentin. However, the vimentin gene lacks a consensus TGFbeta1 response element. By transient transfection analysis of vimentin's various promoter elements fused to the CAT reporter gene, we have determined that tandem AP-1 sites surrounded by GC-boxes are required for TGFbeta1 induction. Mutations within this region eliminated the ability of Smad3 to induce reporter gene expression. DNA precipitation and ChIP assays suggest that c-Jun, c-Fos, Smad3 and Sp1/Sp3 interact over this region, but this interaction changes during myogenesis with TGFbeta1 induction.
Wu
Yongzhong
Y
Department of Biochemistry and the Massey Cancer Center, Medical College of Virginia Campus, Virginia Commonwealth University, Richmond, VA 23298-0614, USA.
Zhang
Xueping
X
Salmon
Morgan
M
Lin
Xia
X
Zehner
Zendra E
ZE
D000818:Animals; D001483:Base Sequence; D002454:Cell Differentiation; D002460:Cell Line; D005786:Gene Expression Regulation / Q000187:drug effects; D017930:Genes, Reporter / Q000235:genetics; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D032448:Myoblasts, Skeletal / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D011485:Protein Binding; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051785:Smad Proteins / Q000145:classification / Q000378:metabolism*; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D014746:Vimentin / Q000235:genetics*; D050880:p300-CBP Transcription Factors / Q000378:metabolism
D016760:Proto-Oncogene Proteins c-fos; D051785:Smad Proteins; D016329:Sp1 Transcription Factor; D018808:Transcription Factor AP-1; D053773:Transforming Growth Factor beta1; D014746:Vimentin; D050880:p300-CBP Transcription Factors; D048031:JNK Mitogen-Activated Protein Kinases