Transcriptional regulation of human organic anion transporter 1 by B-cell CLL/lymphoma 6

Am J Physiol Renal Physiol. 2014 Dec 1;307(11):F1283-91. doi: 10.1152/ajprenal.00426.2014. Epub 2014 Sep 18.

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.

Keywords: B-cell CLL/lymphoma 6; hepatocyte nuclear factor-1; organic anion transporter 1; renal drug transporter; transcriptional regulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • DNA / metabolism
  • DNA-Binding Proteins / genetics*
  • Gene Expression Regulation / genetics*
  • Hepatocyte Nuclear Factor 1-alpha / biosynthesis
  • Hepatocyte Nuclear Factor 1-alpha / genetics
  • Hepatocyte Nuclear Factor 1-alpha / metabolism
  • Humans
  • Kidney / metabolism
  • Mutagenesis, Site-Directed
  • Mutation / genetics
  • Mutation / physiology
  • Opossums / physiology*
  • Organic Anion Transport Protein 1 / biosynthesis*
  • Organic Anion Transport Protein 1 / genetics
  • Promoter Regions, Genetic / genetics
  • Proto-Oncogene Proteins c-bcl-6

Substances

  • BCL6 protein, human
  • DNA-Binding Proteins
  • Hepatocyte Nuclear Factor 1-alpha
  • Organic Anion Transport Protein 1
  • Proto-Oncogene Proteins c-bcl-6
  • DNA