title: C/EBPα represses slow myosin heavy chain 2 gene expression in developing avian myotubes.
abstract: The CCAAT/enhancer binding proteins (C/EBP) comprise a family of transcription factors that regulate many cellular processes. Little is known of their function during embryonic and fetal myogenesis. Slow myosin heavy chain 2 (MyHC2) is a marker of the slow avian skeletal muscle fiber type, and slow MyHC2 gene regulation involves molecular pathways that lead to muscle fiber type diversification.
  
  
  
  The biological effects of C/EBPα and C/EBPβ expression were analyzed by use of a general C/EBP activity reporter and by slow MyHC2 promoter-reporter constructs transfected into specific myogenic cell lineages. The effects of C/EBPα and C/EBPβ expression were also analyzed by immunocytochemical detection of slow MyHC2. C/EBPα interaction with the slow MyHC2 promoter was assessed by electromobility shift assays.
  
  
  
  C/EBPα and C/EBPβ are present in embryonic fast and fast/slow avian myogenic lineages. Overexpression of C/EBPα cDNA repressed slow MyHC2 promoter activity in embryonic myotubes and in both electrically stimulated fetal myotubes. Deletion analysis of the slow MyHC2 promoter-luciferase reporter demonstrated that the transcriptional repression mediated by C/EBPα occurs within the first 222bp upstream from exon 1 of the slow MyHC2 gene. Electromobility shift assays determined that C/EBPα can bind to a non-canonical C/EBP site within the slow MyHC2 gene, and mutation of this site reduced transcriptional repression of the slow MyHC2 gene.
  
  
  
  C/EBPα, but not C/EBPβ, represses slow MyHC2 promoter activity via a non-canonical C/EBP binding element.
  
  
  
  Members of the C/EBP family of transcription factors differentially regulate genes indicative of distinct muscle fiber types.
authors.affiliation: School of Graduate and Postdoctoral Studies and Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, United States.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Cavanaugh
authors.affiliation: School of Graduate and Postdoctoral Studies and Chicago Medical School, Rosalind Franklin University of Medicine and Science, 3333 Green Bay Road, North Chicago, IL 60064, United States. Electronic address: joseph.dimario@rosalindfranklin.edu.
authors.forename: Joseph X
authors.initials: JX
authors.lastname: DiMario
mesh_terms: D000818:Animals; D030161:Avian Proteins / Q000235:genetics / Q000378:metabolism*; D022763:CCAAT-Enhancer-Binding Protein-alpha / Q000378:metabolism*; D002478:Cells, Cultured; D002642:Chick Embryo; D018507:Gene Expression Regulation, Developmental; D024510:Muscle Development; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000235:genetics / Q000378:metabolism*
chemical_list: D030161:Avian Proteins; D022763:CCAAT-Enhancer-Binding Protein-alpha; D018995:Myosin Heavy Chains
keywords: Avian; Fiber type; Lineage; Muscle; Promoter; Transcription