Hepatocyte nuclear factor-3 alpha promoter regulation involves recognition by cell-specific factors, thyroid...

The hepatocyte nuclear factor-3 alpha (HNF-3 alpha) and -3 beta proteins share homology in the winged helix/fork head DNA binding domain and regulate cell-specific transcription in hepatocytes and respiratory epithelium. In this study, we used transfection assays to demonstrate that the -520 nucleotides upstream of the rat HNF-3 alpha gene were sufficient for cell-specific expression. We identified binding sites for a liver and kidney-enriched nuclear factor and a kidney-enriched protein that recognizes two distinct promoter elements. We showed that the rat HNF-3 alpha promoter binds the HNF-3 protein isoforms, which may serve an auto- and/or cross-regulatory role. Furthermore, we showed that cotransfection of the thyroid transcription factor-1 expression vector enhanced HNF-3 alpha promoter activity. We discuss these results with respect to the transcriptional induction of the HNF-3 alpha gene in respiratory epithelium during embryogenesis. Because the HNF-3 alpha promoter region bound nuclear factors in kidney extracts, we used in situ hybridization to demonstrate that it was expressed in the urothelium of the renal pelvis in adult and embryonic kidney. We also report on a novel expression pattern of HNF-3 alpha in the epithelium of the urinary bladder, penile urethra, and the prostate gland, and show that its expression in the intestinal epithelium increases from the proximal duodenum to distal ileum. We also demonstrate that HNF-3 alpha is abundantly expressed in the colonic epithelium. Furthermore, we use the HNF-3 DNA binding consensus sequence to identify putative target genes in the renal pelvis and gut epithelium.