The serum response factor (SRF) is needed for muscle-specific activation of CArG boxes.

CArG boxes, whose consensus sequence is CC(A/T)6GG, are involved in two very different types of transcriptional responses: response of immediate early genes to serum, mediated by so-called Serum Response Elements (SRE), and transcriptional activation of muscle-specific genes during muscle differentiation. Although previous studies have shown that the Serum Response Factor (SRF) binds to muscular CArG boxes, the role of such a binding in muscle-specific activation of CArG box-dependent genes was not directly demonstrated. Here, by transient co-transfection experiments, we demonstrate that intact SRF is required for muscle-specific transcriptional activation through CArG boxes.