p300 and SIRT1 modulate PXR's transcriptional activity. 293T
cells were co-transfected with pSG5-PXR, CYP3A4-Luc (A, C, E, F) or MDR1-Luc
reporter (B, D), and pCMV-β-galactosidase control plasmids. 24 h after
transfection, cells were treated with DMSO, Rif, or SR12813 as indicated for an
additional 24 h. (A, B) Cells were co-transfected with pCDNA3.1. empty vector
control, pCDNA3.1-p300, or pCDNA3.1-p300 ΔHAT mutant as well. (C, D)
Cells were co-transfected with pCDNA3.1. empty vector control, pECE-SIRT1, or
pECE-SIRT1 H363Y. (E) Transfected cells were treated with increasing
concentrations of TSA (E), or NAM (F) at the same time with DMSO or RIF as
indicated. Cells were then lysed and luciferase and β-galactosidase
activities were measured. Luciferase values were normalized to
β-galactosidase activities. The data represents the mean and SEM of at
least 3 independent experiments performed in triplicate. ****p < 0.05,
n.s., not significant 2-way ANOVA. Rif = rifampicin, TSA = Trichostatin A, NAM =
nicotinamide.