FIGURE 13.

The effect of FXR SUMOylation on expression of a 3XFXRE-TK-luciferase construct. 3XFXRE-TK-Luc was constructed by cloning three copies of the Bsep FXRE upstream of the minimal thymidine kinase (TK) promoter and the luciferase opening reading frame. CV-1 cells in 12-well plates were transfected with 3XFXRE-TK-Luc along with wild-type FXR, RXRα, and Sumo1 or the FXR mutants. A, expression of the FXR-RXRα heterodimer along with Sumo1 in CV-1 cells led to a marked decrease in expression of the 3XFXRE-TK-LUC activity in the presence of GW4064. There was no activity of the promoter observed in the absence of FXR/RXRα. Sumo1 failed to decrease 3XFXRE-TK-LUC activity with expression of K122R/K275R/E277A mutant FXR and RXRα in the presence of ligand. *, p < 0.001 compared with transfection in the absence of FXR/RXRα or with mutant FXR. B, expression of the FXR-RXRα heterodimer along with SUMO2 in CV-1 cells had no effect on expression of 3XFXRE-TK-LUC activity in the presence of GW4064.