Fig. 5.

PXR.2 can compete with PXR.1 for rifampin activation of reporter plasmids. HepG2 cells were transfected with expression vectors encoding PXR.1 or PXR.2 (A and B) pCMX-Gal4-PXR or pMSCV-hPXR-IRES-GFP (C and D) with appropriate reporter genes as described under Materials and Methods and treated for 48 h with 10 μM rifampin and relative reporter activity graphed relative to cells without cotransfected PXR. B and D, a constant amount of PXR.1 (10 ng) was cotransfected with increasing amounts of PXR.2 and the reporter plasmids. Values represent the mean ± S.D. measured in triplicate in at least two independent transfections. The ratio of PXR.2 to PXR.1 expression plasmid was graphed relative to activation of reporter genes.