Fgf induces transfected bck promoter driven expression in skeletal muscle by specifically increasing binding affinity of a nuclear protein. Kim, Lucy, Amy Steves, Margaret Collins, Jenny Fu, and Michael E. Ritchie. Division of Cardiology and Cardiovascular Research Center, University of Cincinnati College of Medicine, 231 Bethesda Avenue, Cincinnati, Ohio 45267-0542 and Division of Cardiology, Veterans Administration Medical Center, 3200 Vine Street, Cincinnati, Ohio 45220
APStracts 3:0349C, 1996.
Changes in gene expression occurring during skeletal muscle differentiation are exemplified by down regulation of brain creatine kinase (BCK) and induction of muscle (M) CK. Though 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, following switch to differentiation medium, were treated with bFGF, bFGF + Herbimycin, cAMP, or phorbol 12 -myristate 13-acetate (PMA). Analyses demonstrated that bFGF responsiveness was contained within a 33 bp element. Electromobility shift assays showed that FGF induction increased 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. 

Received 7 June 1996; accepted in final form 18 October 1996.
APS Manuscript Number C320-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 November 1996