title: Transcriptional regulation of the type I myosin heavy chain gene in denervated rat soleus.
abstract: Denervation (DEN) of rat soleus is associated with a decreased expression of slow type I myosin heavy chain (MHC) and an increased expression of the faster MHC isoforms. The molecular mechanisms behind these shifts remain unclear. We first investigated endogenous transcriptional activity of the type I MHC gene in normal and denervated soleus muscles via pre-mRNA analysis. Our results suggest that the type I MHC gene is regulated via transcriptional processes in the denervated soleus. Deletion and mutational analysis of the rat type I MHC promoter was then used to identify cis elements or regions of the promoter involved in this response. DEN significantly decreased in vivo activity of the -3,500, -2,500, -914, -408, -299, and -215 bp type I MHC promoters, relative to the alpha-skeletal actin promoter. In contrast, normalized -171 promoter activity was unchanged. Mutation of the betae3 element (-214/-190) in the -215 promoter and deletion of this element (-171 promoter) blunted type I downregulation with DEN. In contrast, betae3 mutation in the -408 promoters was not effective in attenuating the DEN response, suggesting the existence of additional DEN-responsive sites between -408 and -215. Western blotting and gel mobility supershift assays demonstrated decreased expression and DNA binding of transcription enhancer factor 1 (TEF-1) with DEN, suggesting that this decrease may contribute to type I MHC downregulation in denervated muscle.
authors.affiliation: Department of Physiology and Biophysics, University of California, Irvine 92697, USA.
authors.forename: K A
authors.initials: KA
authors.lastname: Huey
authors.forename: F
authors.initials: F
authors.lastname: Haddad
authors.forename: A X
authors.initials: AX
authors.lastname: Qin
authors.forename: K M
authors.initials: KM
authors.lastname: Baldwin
mesh_terms: D000818:Animals; D001835:Body Weight / Q000502:physiology; D004268:DNA-Binding Proteins / Q000235:genetics; D003714:Denervation; D005260:Female; D017353:Gene Deletion; D005786:Gene Expression Regulation / Q000235:genetics; D005809:Genes, Regulator / Q000235:genetics*; D018482:Muscle, Skeletal / Q000294:innervation* / Q000378:metabolism* / Q000503:physiopathology; D009154:Mutation / Q000235:genetics; D018995:Myosin Heavy Chains / Q000235:genetics*; D024461:Myosin Type I / Q000235:genetics*; D024462:Myosin Type II / Q000235:genetics; D009687:Nuclear Proteins; D009929:Organ Size / Q000502:physiology; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000091262:TEA Domain Transcription Factors; D014157:Transcription Factors / Q000235:genetics
chemical_list: D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D012333:RNA, Messenger; D000091262:TEA Domain Transcription Factors; C057182:TEAD1 protein, human; D014157:Transcription Factors; D024461:Myosin Type I; D024462:Myosin Type II; D018995:Myosin Heavy Chains