title: Estrogen receptor alpha, fos-related antigen-2, and c-Jun coordinately regulate human UDP glucuronosyltransferase 2B15 and 2B17 expression in response to 17beta-estradiol in MCF-7 cells.
abstract: UDP-glucuronosyltransferase 2B15 and 2B17 expression is up-regulated by 17beta-estradiol in MCF-7 breast cancer cells, as assessed by quantitative real-time polymerase chain reaction. Using 5'-deletion mapping and site-directed mutagenesis, we demonstrate that 17beta-estradiol activation of UGT2B15 gene transcription is mediated by a 282-base pair fragment positioned -454 to -172 nucleotides from the translation start site. This region contains two putative activator protein-1 (AP-1) elements, one imperfect estrogen response element (ERE), and two consensus ERE half-sites. We propose that these five sites act as an estrogen response unit (ERU), because mutation in any site reduces activation of the UGT2B15 promoter by 17beta-estradiol. Despite the presence of two AP-1 elements, the UGT2B15 promoter is not responsive to the AP-1 activator phorbol 12-myristate 13-acetate. Although electrophoretic mobility shift assays (EMSA) indicate that the AP-1 proteins c-Jun and Fos-related antigen 2 (Fra-2) bound to the distal AP-1 site, binding of Jun or Fos family members to the proximal AP-1 site was not detected by EMSA. Chromatin immunoprecipitation assays showed a 17beta-estradiol-induced recruitment of estrogen receptor (ER) alpha, c-Jun, and Fra-2 to the 282-bp ERU. The involvement of these three transcription factors in the stimulation of UGT2B15 gene expression by 17beta-estradiol was confirmed by siRNA silencing experiments. Mutagenesis and siRNA experiments indicate that UGT2B17 expression is also regulated by 17beta-estradiol via the ERU, which is fully conserved in both promoters. Because UGT2B15 and UGT2B17 inactivate steroid hormones by glucuronidation, the regulation of their genes by 17beta-estradiol may maintain steroid hormone homeostasis and prevent excessive estrogen signaling activity.
authors.affiliation: Department of Clinical Pharmacology, Flinders Medical Centre, Bedford Park, SA, Australia.
authors.forename: Dong Gui
authors.initials: DG
authors.lastname: Hu
authors.forename: Peter I
authors.initials: PI
authors.lastname: Mackenzie
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism; D045744:Cell Line, Tumor; D004958:Estradiol / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D005260:Female; D051921:Fos-Related Antigen-2 / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D014453:Glucuronosyltransferase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism*
chemical_list: D047628:Estrogen Receptor alpha; D051921:Fos-Related Antigen-2; D016755:Proto-Oncogene Proteins c-jun; D004958:Estradiol; D014453:Glucuronosyltransferase; C472000:UDP-glucuronosyltransferase 2B15, human