title: MEF2B is a component of a smooth muscle-specific complex that binds an A/T-rich element important for smooth muscle myosin heavy chain gene expression.
abstract: To understand smooth muscle-specific gene expression, we have focused our studies on the smooth muscle myosin heavy chain (SMHC) gene, a smooth muscle-specific marker. In this study, we demonstrate that the SMHC promoter region (-1594 to -1462 base pairs) containing the A/T-rich element can activate the heterologous thymidine kinase promoter in smooth muscle cells, but not in fibroblasts. Mutations of this A/T-rich element decreased SMHC promoter activity significantly. Both gel mobility shift assays and DNase I footprinting revealed that this region binds to specific protein complexes from smooth muscle nuclear extracts, whereas nuclear extracts from skeletal muscle and fibroblasts produced a different binding pattern. We also demonstrate that the protein complex obtained from smooth muscle nuclear extract reacts with MEF2B-specific antibody, but not with antibodies specific to MEF2A, MEF2C, or MEF2D, suggesting that only MEF2B protein binds to the A/T-rich element. Furthermore, MEF2B overexpression in smooth muscle cells up-regulated the SMHC promoter, suggesting that MEF2B is important for SMHC gene regulation. This is the first report demonstrating a role for MEF2 factors in smooth muscle-specific gene expression.
authors.affiliation: Section of Molecular Cardiology, University of Cincinnati, Ohio 45267, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Katoh
authors.forename: J D
authors.initials: JD
authors.lastname: Molkentin
authors.forename: V
authors.initials: V
authors.lastname: Dave
authors.forename: E N
authors.initials: EN
authors.lastname: Olson
authors.forename: M
authors.initials: M
authors.lastname: Periasamy
mesh_terms: D016475:3T3 Cells; D000818:Animals; D000906:Antibodies / Q000378:metabolism; D001483:Base Sequence; D018983:DNA Footprinting; D004268:DNA-Binding Proteins / Q000276:immunology / Q000502:physiology*; D015870:Gene Expression; D064326:MEF2 Transcription Factors; D051379:Mice; D008969:Molecular Sequence Data; D009130:Muscle, Smooth; D009131:Muscle, Smooth, Vascular / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D018006:Myogenic Regulatory Factors; D018995:Myosin Heavy Chains / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D011817:Rabbits; D013937:Thymidine Kinase / Q000235:genetics; D014157:Transcription Factors / Q000276:immunology / Q000502:physiology*; D014162:Transfection; D015854:Up-Regulation
chemical_list: D000906:Antibodies; D004268:DNA-Binding Proteins; D064326:MEF2 Transcription Factors; C578036:Mef2a protein, mouse; C578039:Mef2b protein, mouse; C578041:Mef2c protein, mouse; C578044:Mef2d protein, mouse; D018006:Myogenic Regulatory Factors; D014157:Transcription Factors; D013937:Thymidine Kinase; D018995:Myosin Heavy Chains