Fig. 6.
Phosphomimetic mutation at Thr57 does not affect hPXR interaction with SRC-1. Mammalian two-hybrid assays were performed in HepG2 cells transiently cotransfected with plasmids encoding Gal4-SRC-1 and the reporter gene pG5-luc, along with empty vector pACT, VP16-hPXR, VP16-hPXRT57A, or VP16-hPXRT57D, as indicated. The cells were treated with DMSO or 5 μM rifampicin (RIF) 24 h after transfection. Luciferase assays were performed 24 h after the compound treatment. The relative luminescence for pG5-luc was determined by normalizing firefly luciferase activity with Renilla luciferase activity. The values represent the means of eight independent experiments, and the bars denote the S.D. The Student's t test was used to determine statistical significance of unpaired samples by comparing the relative luminescence obtained between the samples cotransfected with the vector and hPXR plasmids for corresponding DMSO or rifampicin treatments. Comparisons between other samples were noted in brackets. Differences were considered significant for p < 0.05 (*), 0.01 (**), or 0.001 (***), and nonsignificant (N.S.) for p > 0.05. SRC-1, Gal4-SRC-1; hPXR, VP16-hPXR; hPXRT57A, VP16-hPXRT57A; hPXRT57D, VP16-hPXRT57D.