bFGF induces BCK promoter-driven expression in muscle via increased binding of a nuclear protein.
Changes in gene expression occurring during skeletal muscle differentiation are exemplified by downregulation of brain creatine kinase (BCK) and induction of muscle creatine kinase (MCK). Although both are transcriptionally regulated, there appears to be no transcription factor-element overlap, suggesting that their coordinate expression results from culture medium-related influences. Basic fibroblast growth factor (bFGF) prevents myogenesis and represses MCK expression by inhibiting transcriptional activation. It was hypothesized that bFGF similarly influenced BCK by inducing its expression. Accordingly, BCK promoter constructs were transiently transfected into C2C12 cells and, after a switch to differentiation medium, were treated with bFGF, bFGF plus herbimycin, adenosine 3',5'-cyclic monophosphate (cAMP), or phorbol 12-myristate 13-acetate (PMA). Analyses demonstrated that bFGF responsiveness was contained within a 33-base pair element. Electromobility shift assays showed that bFGF induction increased the abundance of the nuclear factor binding the element. Both effects were prevented by herbimycin. Neither cAMP nor PMA specifically induced the construct containing the bFGF-responsive element. The induced factor required phosphorylation to bind, implying that bFGF-mediated increases in binding may be due to transcription factor phosphorylation.
Kim
L
L
Division of Cardiology, University of Cincinnati College of Medicine, Ohio 45267-0542, USA.
Steves
A
A
Collins
M
M
Fu
J
J
Ritchie
M E
ME
D000818:Animals; D001483:Base Sequence; D016227:Benzoquinones; D001921:Brain / Q000201:enzymology; D003994:Bucladesine / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003402:Creatine Kinase / Q000096:biosynthesis* / Q000235:genetics*; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects*; D016222:Fibroblast Growth Factor 2 / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D007527:Isoenzymes; D047029:Lactams, Macrocyclic; D051379:Mice; D018482:Muscle, Skeletal / Q000166:cytology / Q000201:enzymology*; D009687:Nuclear Proteins / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000187:drug effects*; D011809:Quinones / Q000494:pharmacology; D011994:Recombinant Proteins / Q000096:biosynthesis; D017828:Rifabutin / Q000031:analogs & derivatives; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection
D016227:Benzoquinones; D007527:Isoenzymes; D047029:Lactams, Macrocyclic; D009687:Nuclear Proteins; D011809:Quinones; D011994:Recombinant Proteins; D016222:Fibroblast Growth Factor 2; D017828:Rifabutin; D003994:Bucladesine; C020754:herbimycin; D000242:Cyclic AMP; D003402:Creatine Kinase; D013755:Tetradecanoylphorbol Acetate