Fig. 1.

PXR downregulates transcription of the HNF4α gene in HepG2 cells. (A) Parental HepG2 and ShP51 cells were harvested at each time point after RIF treatment, and then total RNAs were prepared and subjected to real-time PCR. The levels of the total HNF4α and CYP3A4 mRNAs are expressed by taking their levels in the DMSO-treated parental HepG2 cells as one. Columns represent the mean ± S.D. from three independent experiments in triplicate. *P < 0.05 versus DMSO (Student’s t test); **P < 0.01 versus DMSO (Student’s t test). (B) Twenty-four hours after RIF treatment, total RNAs were prepared from cells and subjected to real-time PCR using specific probes for transcripts derived from the HNF4α P1 and P1 promoters. The levels of HNF4α transcripts are expressed by taking the HNF4α P1 promoter-derived transcripts in the DMSO-treated parental HepG2 cells as one. Columns represent the mean ± S.D. from three independent experiments in triplicate. *P < 0.05 versus DMSO (Student’s t test); **P < 0.01 versus DMSO (Student’s t test). (C) At time points of 12 and 24 hours after treatment with DMSO or RIF, whole-cell lysates were prepared and subjected to Western blotting using the following antibodies: total HNF4α, HNF4α-P1, HNF4α-P2, and actin. One representative of three independent experiments is shown. DM, DMSO.