Fig. 4.

Effect of mutation of the BSEP NF-κB binding site on the transactivation of BSEP promoter. Huh-7 cells were transiently transfected with FXR/RXR and plasmid vectors containing the BSEP promoter sequences that either included the NF-κBE or with a construct of a mutated NF-κB binding site linked to luciferase as reporter. A: suppression of the BSEP promoter by NF-κB p65 was dose dependent and reversed by expression of the IκBα super-repressor. When The NF-κB binding site in the BSEP promoter was mutated (B), NF-κB p65 still dose dependently inhibited ligand-induced transactivation of the mutant BSEP promoter, and this effect was reversed by expression of the IκBα super-repressor. However, at the lowest dose of NF-κB p65 overexpression (25 ng), the majority of inhibition could be attributed to the NF-κB binding site (∼57% inhibition with the wild-type promoter vs. ∼17% with the promoter after mutation of the NF-κB binding site). Each histogram is ±SE from representative experiments done at least 3 times. #P < 0.05.