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Biochem Pharmacol. 2014 Feb 15;87(4):660-7. doi: 10.1016/j.bcp.2013.11.001. Epub 2013 Nov 14.

Epigenetic regulation of the tissue-specific expression of human UDP-glucuronosyltransferase (UGT) 1A10.

Author information

1
Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
2
Drug Metabolism and Toxicology, Faculty of Pharmaceutical Sciences, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan. Electronic address: nmiki@p.kanazawa-u.ac.jp.

Abstract

Human UDP-glucuronosyltransferase (UGT) 1A10 is not expressed in the liver; however, UGT1A10 is highly expressed in the intestine, contributing to presystemic first-pass metabolism. Earlier studies revealed that hepatocyte nuclear factor (HNF) 1α and Sp1, as well as an intestine-specific transcription factor, caudal type homeobox (Cdx) 2, are involved in the constitutive expression of UGT1A10. However, why UGT1A10 is not expressed in the liver, where HNF1α and Sp1 are abundantly expressed, is unknown. In this study, we sought to elucidate the mechanism, focusing on epigenetic regulation. Bisulfite sequence analysis revealed that the CpG-rich region (-264 to +117) around the UGT1A10 promoter was hypermethylated (89%) in hepatocytes, whereas the UGT1A10 promoter was hypomethylated (11%) in the epithelium of the small intestine. A luciferase assay revealed that the methylation of the UGT1A10 promoter by SssI methylase abrogated transactivity even with overexpressed Cdx2 and HNF1α. The UGT1A10 promoter was highly methylated (86%) in liver-derived HuH-7 cells, where UGT1A10 is not expressed. In contrast, the UGT1A10 promoter was hardly methylated (19%) in colon-derived LS180 cells, where UGT1A10 is expressed. Treatment with 5-aza-2'-deoxycitidine (5-Aza-dC), an inhibitor of DNA methylation, resulted in an increase in UGT1A10 expression only in HuH-7 cells. Moreover, overexpression of HNF1α and Cdx2 further increased UGT1A10 expression only in the presence of 5-Aza-dC. Collectively, we found that DNA hypermethylation would interfere with the binding of HNF1α and Cdx2, resulting in the defective expression of UGT1A10 in human liver. Thus, epigenetic regulation is one of the mechanisms that determine the tissue-specific expression of UGT1A10.

KEYWORDS:

DNA methylation; Epigenetics; Tissue-specific regulation; UDP-glucuronosyltransferase

PMID:
24239897
DOI:
10.1016/j.bcp.2013.11.001
[Indexed for MEDLINE]

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