Cdc42 regulates β1 integrin transcription via SRF. (A) β1 integrin mRNA levels quantified by quantitative PCR. (B–G) Activities of p3000 β1 integrin and c-fos promoters were assessed by luciferase assays after PC3 cell transfection with the indicated siRNAs (B), Cos7 cell transfection with wild-type or constitutively active Cdc42-V12 (C and D), Cos7 cell transfection with Cdc42-V12 and RhoA siRNAs (E), PC3 cell transfection with the indicated siRNAs (F), and Cos7 cell transfection with SRF siRNAs (G). (H) Lysates of PC3 cells transfected as indicated were immunoblotted for SRF, β1 integrin, and GAPDH (loading control). A representative blot is shown (left) as well as a quantification of three independent blots for β1 integrin (right). (I) Time of intercalation for individual cells, expressed as the percentage of the total cell number. PC3 cells were transfected with SRF-VP16 24 h after siRNA transfection. Values are means ± SEM (error bars; n = 3); ***, P < 0.001; **, P < 0.01; *, P < 0.05.