Functions of PXR, NCOA6, and p300 in the induction of CYP3A4 by rifampicin. Knockdown of target genes by RNA interference (RNAi) in LS174T cells was performed by transfection of shRNA plasmids. Transiently or stably transfected cells were treated with a solvent DMSO control (0.1%, v/v) or rifampicin (10 μM) for 48 hours before RNA isolation. Knockdown of PXR by RNAi on mRNA (A) and protein levels (B). Effect of silencing PXR expression on CYP3A4 mRNA and the induction by rifampicin (C). Knockdown of NCOA6 by RNAi on mRNA (D) and protein levels (E). Effect of silencing NCOA6 expression on CYP3A4 mRNA and induction by rifampicin (F). Knockdown of p300 by RNAi on mRNA (G) and protein levels (H). Effect of silencing p300 expression on CYP3A4 mRNA and induction by rifampicin (I). Data are shown as mean ± S.D. of three independent experiments. *p < 0.05, **p < 0.01versus control (Student’s t test or one-way analysis of variance followed by Bonferroni’s post-hoc test). RIF, rifampicin.