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Nucleic Acids Research Advance Access published online on January 7, 2009
Nucleic Acids Research, doi:10.1093/nar/gkn1047
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© 2009 The Author(s)
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Molecular Biology

Identification of pregnane-X receptor target genes and coactivator and corepressor binding to promoter elements in human hepatocytes

Niresh Hariparsad1,*, Xiaoyan Chu1, Jocelyn Yabut1, Paul Labhart2, Dylan P. Hartley1, Xudong Dai2 and Raymond Evers

1Department of Drug Metabolism and Pharmacokinetics, Merck & Co, Rahway, NJ 07065, 2Genpathway, Inc., San Diego, CA 92121 and 3Rosetta Inpharmatics LLC, a wholly owned subsidiary of Merck & Co., Inc., WA 98109, USA

*To whom correspondence should be addressed. Tel: +1 732 594 6284; Fax: +1 732 594 2382; Email: niresh_hariparsad{at}merck.com

Received August 9, 2008. Revised December 11, 2008. Accepted December 15, 2008.

Chromatin immunoprecipitation (ChIP) studies were conducted in human hepatocytes treated with rifampicin in order to identify new pregnane-X receptor (PXR) target genes. Genes, both previously known to be involved and not known to be involved in drug disposition, with PXR response elements (PXREs) located upstream, within or downstream from their potentially associated genes, were identified. Validation experiments identified several new drug disposition genes with PXR binding sites. Of these, only CYP4F12 demonstrated increased binding in the presence of rifampicin. The role of PXR in the basal and inductive response of CYP4F12 was confirmed in hepatocytes in which PXR was silenced. We also assessed the association of PXR-coactivators and -corepressors with known and newly identified PXREs. Both PXR and the steroid receptor coactivator (SRC-1) were found to bind to PXREs in the absence of rifampicin, although binding was stronger after rifampicin treatment. We observed promoter-dependent patterns with respect to the binding of various coactivators and corepressors involved in the regulation of CYP4F12, CYP3A4, CYP2B6, UGT1A1 and P-glycoprotein. In conclusion, our findings indicate that PXR is involved in the regulation of CYP4F12 and that PXR along with SRC1 binds to a broad range of promoters but that many of these are not inducible by rifampicin.


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