Fig. 5. GE modulated BSEP transactivation through FXR signaling pathway. (A) Schematic overview of the human BSEP promoter contains an FXRE construct used in this study. (B) Induction of BSEP promoter activity by GE (25, 50, and 100 μM) or GW4064 (5 μM). HepG2 cells were cotransfected with BSEP promoter reporter, FXR expression construct, and the null-Renilla luciferase plasmid. Luciferase activities were measured by the Dual Luciferase Reporter assay system. Relative luciferase activities are shown as mean ± S.E.M. (n = 5). *P < 0.05, **P < 0.01, ***P < 0.001, significantly different from the activities in corresponding vehicle-treated cells. ChIP assay of FXR binding to the BSEP promoter was carried out using chromatins prepared from HepG2 cells treated with DMSO (0.1%) or GE (100 μM). After immunoprecipitated with anti-FXR or IgG, recruitment of FXR to the promoters of BSEP was detected by (C) PCR and (D) qRT-PCR. Input chromatin DNA was included as a positive PCR control. Values are plotted as fold relative to the signal obtained with IgG. Data are the mean ± S.E.M. (n = 5). ***P < 0.001, GE treatment compared with DMSO.