Fig. 3.

Zyxin potentiates the transcriptional activity of HNF-1β. A: HeLa cells were cotransfected with a luciferase reporter plasmid containing the Pkhd1 promoter and expression plasmids encoding HNF-1β alone, zyxin alone, or both HNF-1β and zyxin. Luciferase activity was measured 48 h after transfection. Luciferase activity was increased in cells transfected with both HNF-1β and zyxin but not zyxin alone. *P < 0.05, compared with pcDNA; **P < 0.05. B: mIMCD3 cells were cotransfected with increasing amounts of plasmids encoding zyxin and a constant amount of luciferase reporter plasmid containing the wild-type Pkhd1 promoter (solid bars) or a mutated promoter containing point mutations that prevent HNF-1β binding (gray bars). Zyxin produced a dose-dependent stimulation of the wild-type promoter but had no effect on the mutant promoter. *P < 0.05. C: endogenous zyxin was immunoprecipitated from mIMCD3 cells using an anti-zyxin antibody, and coprecipitated proteins were detected by Western blotting with anti-HNF-1β or anti-CREB binding protein (CBP) antibodies. Bottom: expression in whole cell lysates. Results represent the means of 3 independent experiments. Error bars indicate SD.