Molecular Biology Reports

, Volume 35, Issue 3, pp 361–367

Induction of human UGT1A1 by a complex of dexamethasone-GR dependent on proximal site and independent of PBREM

Authors

  • Takuya Kuno
    • Graduate School of Pharmaceutical SciencesNagoya City University
  • Hiroshi Togawa
    • Graduate School of Pharmaceutical SciencesNagoya City University
    • Graduate School of Pharmaceutical SciencesNagoya City University
Article

DOI: 10.1007/s11033-007-9094-2

Cite this article as:
Kuno, T., Togawa, H. & Mizutani, T. Mol Biol Rep (2008) 35: 361. doi:10.1007/s11033-007-9094-2

Abstract

UDP-glucuronosyltransferase 1A1 (UGT1A1) plays a key role to conjugate bilirubin and prevent jaundice. There are two major elements for the induction of UGT1A1, such as PBREM (−3483/−3194), far from the promoter site, and HNF1 (−75/−63), near to the promoter site. In a previous report, we showed that the proximal HNF1 site is essential for the induction of UGT1A1 by glucocorticoid receptor (GR). In this report, we investigated the influence of PBREM on the induction of the UGT1A1 reporter gene by GR and PXR with dexamethasone (DEX). We confirmed that GR was transferred from cytosol into the nucleus in 15–30 min by DEX stimulation, but HNF1 was not. We constructed a reporter gene containing PBREM to compare the induction of the reporter gene without PBREM by DEX-GR. The results show that induction of the reporter gene with PBREM by DEX at 100 μM is the same level as the induction of the reporter gene without PBREM, although PBREM contains GRE. Co-transfection of hGR with the reporter gene did not show any influence of the induction of the reporter gene between the vector with and without PBREM. Meanwhile, by co-transfection of hPXR, the induction of the reporter gene with PBREM was significantly more than the induction of the reporter gene without PBREM at 100 μM DEX. This supports that hPXR induced UGT1A1 through PBREM by DEX. These results showed that PBREM has no relation with the induction by DEX-GR but the proximal site of UGT1A1 may function in stimulation by DEX-GR.

Keywords

UDP-glucuronosyltransferaseUGT1A1GRDexamethasone

Abbreviations

UGT

UDP-glucuronosyltransferase

PBREM

Phenobarbital responsive enhancer module

GR

Glucocorticoid receptor

HNF

Hepatocyte nuclear factor

DEX

Dexamethasone

PXR

Pregnane-X receptor

NE

Nuclear extract

Copyright information

© Springer Science+Business Media B.V. 2007