FIGURE 3.

Smad3 acts on the enhancer on TGF‐β1 promoter. A, SGC‐7901‐LKB1 cells were transfected with Smad3 siRNA or scrambled siRNA as a control. Forty‐eight hours later, cell extracts were blotted with antibodies as indicated. B, The promoter fragment containing 1.35 kb 5′ of transcription start site (TGBP1) and the same fragment deleted of the putative Smad3 binding site (TGTCTGCCTC, SBE‐mutant) were cloned into the firefly luciferase reporter plasmid and co‐transfected with Renilla luciferase plasmid with or without the active mutant of Smad3 (Smad3‐SD) into SGC‐7901‐LKB1 cells. Luciferase activity in the cell lysates was measured and normalized to Renilla activity. The assays were performed in triplicates (mean ± SD). One‐way ANOVA was used to assess significance of differences between TGBP1 and tested groups. *P < .05, ***P < .001