Functional overload increases beta-MHC promoter activity in rodent fast muscle via the proximal MCAT (betae3) site.
Functional overload (OL) of the rat plantaris muscle by the removal of synergistic muscles induces a shift in the myosin heavy chain (MHC) isoform expression profile from the fast isoforms toward the slow type I, or, beta-MHC isoform. Different length rat beta-MHC promoters were linked to a firefly luciferase reporter gene and injected in control and OL plantaris muscles. Reporter activities of -3,500, -914, -408, and -215 bp promoters increased in response to 1 wk of OL. The smallest -171 bp promoter was not responsive to OL. Mutation analyses of putative regulatory elements within the -171 and -408 bp region were performed. The -408 bp promoters containing mutations of the betae1, distal muscle CAT (MCAT; betae2), CACC, or A/T-rich (GATA), were still responsive to OL. Only the proximal MCAT (betae3) mutation abolished the OL response. Gel mobility shift assays revealed a significantly higher level of complex formation of the betae3 probe with nuclear protein from OL plantaris compared with control plantaris. These results suggest that the betae3 site functions as a putative OL-responsive element in the rat beta-MHC gene promoter.
Giger
Julia M
JM
Department of Physiology and Biophysics, University of California-Irvine, Irvine, CA 92697, USA.
Haddad
Fadia
F
Qin
Anqi X
AX
Baldwin
Kenneth M
KM
D000818:Animals; D001696:Biomechanical Phenomena; D001835:Body Weight; D005260:Female; D017930:Genes, Reporter; D006801:Humans; D006984:Hypertrophy; D018656:Muscle Fibers, Fast-Twitch; D018482:Muscle, Skeletal / Q000502:physiology*; D016297:Mutagenesis, Site-Directed; D018995:Myosin Heavy Chains / Q000235:genetics* / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D009929:Organ Size; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical
D009687:Nuclear Proteins; D020033:Protein Isoforms; D018995:Myosin Heavy Chains