1. C/EBPα represses slow myosin heavy chain 2 gene expression in developing avian myotubes.
- Author
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Cavanaugh, Eric J. and DiMario, Joseph X.
- Subjects
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MYOSIN , *IMMUNOGLOBULIN heavy chains , *MYOGENESIS , *GENE expression , *GENE enhancers - Abstract
Background 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. Methods 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. Results 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 222 bp 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. Conclusion C/EBPα, but not C/EBPβ, represses slow MyHC2 promoter activity via a non-canonical C/EBP binding element. General significance Members of the C/EBP family of transcription factors differentially regulate genes indicative of distinct muscle fiber types. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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