FIG. 2.

Repression of PXR reporters and reversal of Thaps suppression of PXR expression. A, Repression of PXR promoter reporters HepG2 cells were transiently transfected by FuGene HD with a mixture containing 50 ng of a reporter, or the vector along with 5 ng of the null-Renilla luciferase plasmid. The transfected cells were then treated with DMSO or Thaps at 50 nM for 24 h. Luciferase activities were determined with a Dual-Luciferase Reporter Assay System and the signals were expressed as percentages of the normalized luciferase activity (Thaps over solvent). Below is the diagram with reported transcription start sites numbered according to Kurose et al. (2005). Asterisk signs indicate statistical significance from the vector control (P < 0.05). B, Repression of PXR element reporters HepG2 cells were transfected with an element reporter (wild type of a mutant) and treated as described above. Once gain, the luciferase activity was expressed after normalization. Asterisk signs indicate statistical significance from the vector control (P < 0.05). C, Reversal of Thaps-suppression of PXR by LAP or HNF4α. HepG2 cells were transfected with an expression construct (LAP or HNF4α) or the corresponding vector. After an overnight incubation, the transfected cells were treated with Thaps at 50 nM for 24 h. Cells were collected and total RNA was isolated. The level of PXR mRNA was determined by RT-qPCR. The level of PXR in vector-transfected and DMSO-treated cells was expressed as 100%. Asterisk signs indicate statistical significance from the vector (P < 0.05).