Segregation of βMHC regulatory elements: Mechanical overload versus hindlimb suspension

Richard W. Tsika, John J. McCarthy, John R. Gardner, Dharmesh Vyas

Research output: Contribution to journalArticlepeer-review


We have shown that 600 base pairs (bp) of beta-myosin heavy chain (βMHC) promoter was sufficient to direct both increased and decreased βMHC expression in response to either mechanical overload (MOV) or hindlimb suspension (NWB), respectively. To determine if altered βMHC expression in response to MOV or NWB is modulated by the same DNA regulatory element, we have generated transgenic mice harboring a transgene carrying 293 bp of βMHC promoter fused to the chloramphenicol acetyltransferase (CAT) reporter gene (β293). Analysis of 4 independent β293 lines revealed a 43% decrease in endogenous βMHC mRNA in the NWB soleus, while an unexpected increase (20 to 100%) in exogenous CAT mRNA and specific activity was measured. After 8 weeks of MOV, endogenous βMHC mRNA, exogenous CAT mRNA and specific activity increased (3 to 10 fold) as expected. Nuclear extract isolated from NWB and control soleus muscle was used in gel mobility shift assays (OMSA) to assess changes in DNA-nuclear protein interactions at two DNA regulatory elements: 1) the MCAT element (nucleotides -290 to -283) located within transgene β293, and shown to be important for muscle specific expression, and 2) a previously identified negative element (nucleotides -332 to -300) located just upstream of transgene β293. GMSA results suggest a partial role for the MCAT element, but not the negative element, in directing βMHC expression and the slow to fast fiber transition during NWB. Northern analysis showing differential expression of TEF isoforms supports this notion. These results represent the first demonstration that diverse modes of neuromuscular activity effect βMHC expression via segregated βMHC promoter elements, and further suggest that different signaling pathways are likely involved.

Original languageEnglish
Pages (from-to)A666
JournalFASEB Journal
Issue number5
StatePublished - Mar 20 1998

ASJC Scopus subject areas

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics


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