Fig. 6.

FXRα1 transactivated human BSEP through a newly identified FXRE, IR1b. (A) Full-length and minimal human BSEP promoter reporters phBSEP(-2.6kb) and phBSEP(-125b) were cotransfected with FXRα1 in Huh 7 cells. Sixteen hours posttransfection, cells were treated with DMSO (0.1%) and CDCA (10 μM) for 30 h, followed by detection luciferase activities with dual-luciferase reporter assay system. The data are presented as mean ± SD of at least three repeated experiments. (B) A diagram showing the positions of the six elements in the minimal promoter region. (C) The six elements were cloned into the pGL3/p-Luc vector, resulting in six element reporters, pElement 1 to 6. Activation of the six element reporters by FXRα1 in the presence of CDCA (10 μM) was detected by the dual-luciferase reporter assay system. The data are presented as mean ± SD of at least three repeated experiments. *P < 0.05 between DMSO and CDCA-treated cells (Student t-test). (D) The location and sequence of the newly identified IR1b are shown in the upper panel. Transactivation of hIR1a and IR1b reporters by FXRα1 are presented in the lower panel. Reporters pTK-3xhIR1a and pTK-3xIR1b were cotransfected into Huh 7 cells with FXRα1, followed by treating the cells with DMSO (0.1%) or CDCA (10 μM) for 30 h prior to detection of luciferase activities as described in (A). *P < 0.05 between DMSO and CDCA-treated cells (Student t-test).