Cardiac and skeletal transcription factors GATA4, Nkx2.5, myocardin, SRF, MEF2, and other myogenic regulatory factors (MRFs) regulate the expression of miR-1/133/206 polycistronic loci. The subsequent transcription of miR-1 promotes myocyte differentiation through the repression of HDAC4, which in turn represses MEF2. miR-133 promotes myocyte proliferation by repressing SRF. Thus, a feedback loop is created in which miR-1 and miR-133 and their respective transcription factors regulate each others expression.