Tissue specific differences in the regulation of the UDP glucuronosyltransferase 2B17 gene promoter

Abstract

The human UDP glucuronosyltransferase UGT2B17, glucuronidates androgens and is expressed in the liver and the prostate. Although evidence suggests that variations in UGT2B17 expression between tissues may be a critical determinant of androgen response, the factors that regulate UGT2B17 expression in the liver and prostate are unknown. In this study, we have isolated a 596 bp promoter of the UGT2B17 gene and studied its regulation in the liver cell line, HepG2 and the prostate cell line, LNCaP. The transcription start site of UGT2B17 was mapped and proteins that bound to the proximal promoter were detected by DNase1 footprint analysis. A region (-40 to -52 bp) which resembled a hepatocyte nuclear factor 1 (HNF1) binding site bound proteins in nuclear extracts from HepG2 cells, but did not bind proteins from LNCaP nuclear extracts. In HepG2 cells, HNF1alpha bound to this region and activated the UGT2B17 promoter, as assessed by functional and gel shift assays. HNF1alpha activation of the promoter was prevented by mutation or deletion of the putative HNF1 site. The related transcription factor HNF1beta, which is present in HepG2 cells, did not activate the promoter. The UGT2B17 promoter could also be activated by exogenous HNF1alpha in LNCaP cells. However, because these cells do not contain HNF1alpha, other transcription factors must regulate the UGT2B17 promoter. Cotransfection experiments showed that HNF1beta, elevates promoter activity in LNCaP cells. This activation did not involve the putative HNF1 region (-40 to -52 bp) since mutation of this region did not affect promoter activation by HNF1beta. These results suggest that the UGT2B17 promoter is regulated by different factors in liver-derived HepG2 and prostate-derived LNCaP cells.

Hepatocyte Nuclear Factor-1α Is a Causal Factor Responsible for Interindividual Differences in the Expression of UDP-Glucuronosyltransferase 2B7 mRNA in Human Livers

“…HNF-1␣ has been reported to be a member of the nuclear receptor superfamily that regulates the mouse and human UGT1A1 gene (Bernard et al, 1999), the mouse UGT1A6 gene (Vasiliou et al, 1997), the rat UGT1A7 gene (Metz et al, 2000), the rat UGT2B1 gene (Hansen et al, 1997), and the human UGT2B17 gene (Gregory et al, 2000). Since the reported 5Ј-flanking sequence of the UGT2B15 gene does not contain a putative HNF-1␣ binding site , it is reasonable that the amount of HNF-1␣ mRNA does not affect the dmd.aspetjournals.org expression levels of UGT2B15 mRNA.…”

A Novel Polymorphism in a Forkhead Box A1 (FOXA1) Binding Site of the Human UDP Glucuronosyltransferase 2B17 Gene Modulates Promoter Activity and Is Associated with Altered Levels of Circulating Androstane-3α,17β-diol Glucuronide

“…The UGT2B17Ϫ694/Ϫ2 promoter construct containing Ϫ155G was generated as described previously (Gregory et al, 2000) and designated 2B17Ϫ694/Ϫ2 "G" (Luc) in the present study. In this article, nucleotides are numbered with ϩ1 as the A of the initiation codon, as recommended by the Gene Nomenclature Committee.…”

“…Studies with gene reporter constructs indicate that basal UGT2B17 gene expression is controlled by interactions between the transcription factors HNF1␣ and Pbx2 in liverderived HepG2 cells but not in prostate-derived LNCaP cells (Gregory et al, 2000;Gregory and Mackenzie, 2002). In the prostate, UGT2B17 is present in basal cells, whereas UGT2B15 is present in luminal cells (Bélanger et al, 2003).…”

Glucuronidation and the Udp-Glucuronosyltransferases in Health and Disease

“…1). The binding of HNF1␣ to this sequence has been confirmed for the UGT1A1 and UGT2B17 genes (Bernard et al, 1999;Gregory et al, 2000). It is interesting to note that this putative HNF1 binding site is present in a similar position in the proximal promoters of those UGT genes that are expressed in the liver, but it is not present in the same position in those genes expressed exclusively in extrahepatic tissues.…”

“…However, unlike HepG2 cells, LNCaP cells do not contain endogenous HNF1␣ but do contain the related transcription factor HNF1␤. The latter appears to be a positive regulator of UGT2B17 expression in these cells and exerts its effects through a site that is distal to the HNF1␣ binding site utilized in HepG2 cells (Gregory et al, 2000). Factors specifying the expression of UGTs in other tissues remain to be identified.…”