Activation of a muscle-specific enhancer by the Ski proto-oncogene

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Abstract
In transgenic mice, muscle-specific expression of the c-ski oncogene induces hypertrophy exclusively in a subset of fast muscle fibers. Here we report that regulatory elements from two genes expressed in fast fibers, myosin light chain 1/3 (MLC) and muscle creatine kinase (MCK), were activated when co-transfected with c-ski expression vectors in myoblasts. The expression from the MLC enhancer was reduced when the c-sW oncogene was cotransfected with MyoD into NIH3T3 fibroblasts. Activation of the MLC enhancer by Ski also occurred In vivo, since bigenic progeny generated by mating MLC-CAT and MSV-sWtransgenic mice displayed higher CAT activity in their muscles than did the MLC-CAT parental line. Identification of gene targets for the fiber-specific action of the c-skl gene product provides a molecular model that could be used for te further dissection of Ski-Induced hypertrophy, both in tissue culture andin vivo.