title: Transcriptional regulation of human organic anion transporter 1 by B-cell CLL/lymphoma 6.
abstract: The human organic anion transporter 1 (OAT1) is crucial for the excretion of organic anions in renal proximal tubular cells and has been classified as a clinically relevant transporter in the kidneys. Our previous study indicated that renal male-predominant expression of rat Oat1 and Oat3 appears to be regulated by transcription factor B-cell CLL/lymphoma 6 (BCL6). The aim of this study was to characterize the effect of BCL6 on human OAT1 promoter and on the transcription of OAT1 mediated by hepatocyte nuclear factor-1α (HNF-1α). Luciferase assays were carried out in opossum kidney (OK) cells transiently transfected with promoter constructs of OAT1, expression vectors for BCL6 and HNF-1α, and the empty control vectors. BCL6 and HNF-1α binding on OAT1 promoter was analyzed using electrophoretic mobility shift assay (EMSA). Protein expression of HNF-1α was investigated by Western blot analysis. Site-directed mutagenesis was used to introduce mutations into BCL6 and HNF-1α binding sites within the OAT1 promoter. BCL6 enhanced the promoter activity of OAT1 independently of predicted BCL6 binding sites but was dependent on HNF-1α response element and HNF-1α protein. Coexpression of BCL6 and HNF-1α induced an additive effect on OAT1 promoter activation compared with BCL6 or HNF-1α alone. BCL6 does not bind directly or indirectly to OAT1 promoter but increases the protein expression of HNF-1α and thereby indirectly enhances OAT1 gene transcription. BCL6 constitutes a promising candidate gene for the regulation of human OAT1 transcription and other renal and/or hepatic drug transporters that have been already shown to be activated by HNF-1α.
authors.affiliation: Department of Systemic Physiology and Pathophysiology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Waja
authors.initials: W
authors.lastname: Wegner
authors.affiliation: Department of Systemic Physiology and Pathophysiology, University Medical Center Göttingen, Göttingen, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Burckhardt
authors.affiliation: Department of Systemic Physiology and Pathophysiology, University Medical Center Göttingen, Göttingen, Germany maja.henjakovic@med.uni-goettingen.de.
authors.forename: Maja
authors.initials: M
authors.lastname: Henjakovic
mesh_terms: D000818:Animals; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics*; D005786:Gene Expression Regulation / Q000235:genetics*; D051538:Hepatocyte Nuclear Factor 1-alpha / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics / Q000502:physiology; D009893:Opossums / Q000502:physiology*; D027362:Organic Anion Transport Protein 1 / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D051560:Proto-Oncogene Proteins c-bcl-6
chemical_list: C084103:BCL6 protein, human; D004268:DNA-Binding Proteins; D051538:Hepatocyte Nuclear Factor 1-alpha; D027362:Organic Anion Transport Protein 1; D051560:Proto-Oncogene Proteins c-bcl-6; D004247:DNA
keywords: B-cell CLL/lymphoma 6; hepatocyte nuclear factor-1; organic anion transporter 1; renal drug transporter; transcriptional regulation