Fig. 6.

HNF1A binds to the specific region of the ABCB1 promoter to suppress transcription. (A–B) The luciferase assay indicated that the transcriptional activation of ABCB1 in PANC-1 cells was inhibited in stable HNF1A-overexpressing cells and enhanced in HNF1A depletion cells. (C) Comparison of the transcriptional suppressive effect of HNF1A to a series of deletion or mutation constructs of the human ABCB1 promoter. Different human ABCB1 promoter-luciferase reporter constructs together with HNF1A were transiently cotransfected in PANC-1 cells. Twenty-four hours after cotransfection, all samples were harvested for luciferase activity experiments. The graph on the right side reveals the relative luciferase activity of the ABCB1 promoter by HNF1A. (D) ChIP analysis of the human ABCB1 promoter. Protein-DNA complexes from PANC-1 cells were harvested for immunoprecipitation with antibodies against IgG (nonspecific) and HNF1A. After cross-link reversal, the coimmunoprecipitated DNA was amplified by PCR using the indicated primers and resolved in 2% agarose gels. Graphs shown are representative results of three repeated assays and are presented as mean ± SD. **p < .01, ***p < 0,001 (Student's t-test).