FUNCTIONAL INVOLVEMENT OF SERUM RESPONSE FACTOR IN THE TRANSCRIPTIONAL REGULATION OF CALDESMON GENE

A 22-bp fragment including the CArG element (CArG1) is essential for t he transcription of the caldesmon gene. In this study, we investigated the effects of serum response factor (SRF) on the functional regulati on of caldesmon promoter in smooth muscle cells. Gel supershift assay revealed that SRF was one component of the CArG1-protein complex. Domi nant-negative mutants of SRF suppressed the promoter activity of calde smon, whereas wild-type SRF overcame this suppression. These results s uggest that SRF functions as a core activating factor of the caldesmon promoter. Furthermore, fractionation of smooth muscle cells' nuclear extracts using DNA affinity paramagnetic particles suggests that SRF t ransactivates the caldesmon promoter in concert with additional factor s in the flow-through fraction recruited to the CArG element. (C) 1998 Academic Press.