FIG. 6.
Myocardin transactivation enhanced by SUMO-1/PIAS1 was SRF dependent. (A) Reporter gene analysis was conducted with CV1 cells transfected with intact or point deletion (del) mutants of Ca-Actin-Luc reporter constructs, as indicated, in the presence of myocardin, SUMO-1, and PIAS1 expression vectors. Data obtained from two separate assays show percent activation for each corresponding group relative to that of the wild-type Ca-Actin-Luc group, which was taken as 100% activation. The X symbol indicates a site-mutated SRE. (B) SRF with deletion of the transactivation domain, SRFΔC, reduced promoter activity elicited by the presence of myocardin, PIAS1, and SUMO-1. (C) SRFΔC abrogated endogenous cardiac gene induction caused by coexpression of myocardin, PIAS1, and SUMO-1 in 10T1/2 cells. (D) K445R preserved physical association with SRF. GST pulldown assays were performed using in vitro-translated 35S-labeled wild-type myocardin or the K445R mutant incubated with either GST or GST-fused SRF.