Figure 3. RASAL1 inhibits SRF activity.

a., Schematic representation of the transcriptional regulatory regions in the α-SMA gene promoter. E1, E box 1 (CACCTG), E2, E box 2 (CACCTG), THR, TGF-β1 hypersensitivity region, CArG, SRF response element (CC(A/T)₆GG), TCE, TGF-β1 control element. b., Suppressive effects of RASAL1 expression (black bar) on α-SMA promoter activity. Test values were normalized to those obtained from cells transfected with an empty vector (white bar), which was set to 1. Data are means ± SD of three independent experiments in LX2 cells. *, p < 0.05 (t-test). c., The CArG-A element was key for the suppressive effects of RASAL1 on α-SMA promoter activity. Reporter constructs with point mutations in the CArG elements (A, B, and A+B) were used. The results are shown as described in b. d., RASAL1 suppressed SRF activity. Reporter constructs containing five SRF response elements in tandem (SRF RE-luc) were used to determine the effects of RASAL1 on SRF activity. Data are means ± SD of three independent experiments in LX2 cells. *, p < 0.05 (t-test). e., LX2 cells with stable knockdown of SRF showed lower α-SMA protein levels. Representative results from three independent experiments are shown.