(A), Diagram showing the location of each promoter mutants and binding sites for predicted transcriptional factors. (B) Removal of promoter regions containing GATA-b and -c sites plus various transcription factor sites increased RGS4 promoter activity. In contrast, site-directed mutagenesis of GATA-a site in P2, P4 and P5 all significantly reduced the corresponding promoter activity. (C) Site-directed mutagenesis of individual or combined binding sites for GATA-a, NFκB and AP1. Cultured colonic SMCs were cotransfected with promoter-less pMlu3 empty vector (Base) or indicated RGS4 promoter vector carrying renilla luciferase and pGL4-CMV vector carrying firefly luciferase (for normalization). After 24 h, the renilla and firefly luciferases were measured separately. The relative fold changes in renilla luciferase activity after normalization by firefly luciferase were expressed as compared with the empty vector. Data represents the mean ± SEM of 3–4 independent experiments. ** P<0.01 indicate statistically significant increase by student’s t test compared with corresponding P1 (B) or P4 (C). ++ p<0.01 indicates significant decrease in GATA-a mutants as compared with corresponding GATA-a non-mutants.