Monosaccharide-induced lipogenesis regulates the human hepatic sex hormone–binding globulin gene
J. Clin. Invest. David M. Selva, et al. 117:3979 doi:10.1172/JCI32249 [Go to this article.]

Figure 5
Competition between HNF-4α and COUP-TF1 at a cis-element within the human SHBG promoter regulates its activity. (A) HNF-4α levels were reduced in HepG2 cells after transient transfection of an HNF-4α siRNA versus a control siRNA oligonucleotide (left), and siRNA-mediated downregulation of HNF-4α reduced human SHBG promoter activity in a luciferase reporter gene assay (right). Data points are shown as mean ± SD of triplicates; **P < 0.01 compared with cells treated with an siRNA control. (B) ChIP assays of HNF-4α and COUP-TF1 binding to the human SHBG promoter (top). As a control for the ChIP, anti–RNA polymerase (RNApol) antibodies were used with human-specific oligonucleotide primers to PCR amplify the GAPDH promoter (bottom). A nonspecific mouse IgG was used in ChIP reactions to control for nonspecific immunoprecipitation. Positive PCR controls of sheared genomic DNA templates indicated the integrity of the input DNA used in the ChIP reactions. (C) Reduction of COUP-TF1 mRNA in HepG2 cells after siCOUP-TF1 treatment (left) did not influence the activity of the human SHBG promoter under basal conditions (right). Data points are shown as mean ± SD of triplicates. (D) Reduction of human SHBG promoter activity after treatment with siHNF-4α was mitigated by cotreatment with siCOUP-TF1. Data points are shown as mean ± SD of triplicates; *P < 0.05, **P < 0.01 compared with cells treated with an siRNA control.