title: Myocyte-specific enhancer-binding factor (MEF-2) regulates alpha-cardiac myosin heavy chain gene expression in vitro and in vivo.
abstract: A myocyte-specific enhancer-binding factor (MEF-2) DNA binding site was identified in the rat alpha-myosin heavy chain (MHC) gene adjacent to the E-box binding site for alpha-MHC binding factor-2 (BF-2). Mutation of the MEF-2 site, within the context of the full-length promoter, reduced activity by 85 and 80% in neonatal cardiomyocytes and the adult heart, respectively. Mutation of the BF-2 site reduced activity approximately 70% in both models. A MEF-2/BF-2 double mutant gave significantly less activity than the BF-2 mutant but not the MEF-2 mutant, suggesting the possibility that BF-2 and MEF-2 interact. Mutations in MEF-2, which decreased functional activity, also abolished MEF-2 DNA binding activity. MEF-2 DNA binding activity was present in the developing heart, reached a peak in the late fetal and early neonatal stages, and then declined to low levels in the adult heart. The adult levels were sufficient to support alpha-MHC gene expression. MEF-2 activity was increased 2-3-fold in the adult heart subjected to a pressure or volume overload. Two working models are proposed as possible explanations of the antithetic relationship between MEF-2 levels and alpha-MHC gene expression.
authors.affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee 53226.
authors.forename: J D
authors.initials: JD
authors.lastname: Molkentin
authors.forename: B E
authors.initials: BE
authors.lastname: Markham
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D001921:Brain / Q000378:metabolism; D006332:Cardiomegaly / Q000378:metabolism; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004047:Diethyl Pyrocarbonate / Q000494:pharmacology; D004742:Enhancer Elements, Genetic; D005786:Gene Expression Regulation / Q000187:drug effects; D064326:MEF2 Transcription Factors; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009206:Myocardium / Q000378:metabolism*; D018006:Myogenic Regulatory Factors; D009218:Myosins / Q000096:biosynthesis*; D009838:Oligodeoxyribonucleotides; D011401:Promoter Regions, Genetic; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000378:metabolism; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection
chemical_list: D004268:DNA-Binding Proteins; D064326:MEF2 Transcription Factors; D018006:Myogenic Regulatory Factors; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D014157:Transcription Factors; D009218:Myosins; D004047:Diethyl Pyrocarbonate