Intronic DNA elements regulate Nrf2 chemical responsiveness of the human microsomal epoxide hydrolase gene (EPHX1) through a far upstream alternative promoter.
In humans, microsomal epoxide hydrolase (mEH) contributes important biological functions that underlie both detoxification and bioactivation fates arising from exposures to foreign chemicals. Previously, we discovered that human mEH gene transcription is initiated from alternative promoters. The respective transcripts are programmed with tissue specificity and the upstream E1b promoter contributes predominantly to mEH expression. The results presented demonstrate that exposures to the Nrf2 activators, sulforaphane (SFN) and tert-butylhydroquinone (tBHQ), markedly activate E1b transcription in human lung and liver cells. Genomic analyses identified two major DNase I hypersensitive regions (HS-1 and HS-2) within the ~15 kb intervening sequence separating E1b from the downstream E1 promoter. In BEAS-2B cells, the Nrf2 effectors, SFN and tBHQ, selectively activated the more distal HS-2 through an antioxidant response element (ARE). An activator protein 1/12-O-tetradecanoylphorbol-13-acetate interaction was further identified within the HS-2 enhancer that functioned to additionally contribute to ARE-mediated induction responsiveness of the E1b promoter. The results demonstrate that ARE modulation, integrated with additional transcriptional complexes, regulates the tissue-specific expression of mEH and that these processes likely coordinate both the protective and bioactivation functions contributed by mEH activities in human tissues.
Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA.
Shengzhong
S
Su
Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA.
Xi
X
Yang
Center for Molecular Toxicology & Carcinogenesis, The Pennsylvania State University, 101 Life Sciences Bldg, University Park, PA 16802, USA. Electronic address: cjo10@psu.edu.
Curtis J
CJ
Omiecinski
D016588:Anticarcinogenic Agents / Q000494:pharmacology; D000975:Antioxidants / Q000494:pharmacology; D015153:Blotting, Western; D001980:Bronchi / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D024202:Electrophoretic Mobility Shift Assay; D004851:Epoxide Hydrolases / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D006873:Hydroquinones / Q000494:pharmacology*; D007438:Introns / Q000235:genetics*; D017879:Isothiocyanates / Q000494:pharmacology*; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism; D051267:NF-E2-Related Factor 2 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013454:Sulfoxides; D014158:Transcription, Genetic / Q000187:drug effects
D016588:Anticarcinogenic Agents; D000975:Antioxidants; D006873:Hydroquinones; D017879:Isothiocyanates; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D013454:Sulfoxides; C018855:2-tert-butylhydroquinone; D004851:Epoxide Hydrolases; C522330:EPHX1 protein, human; C016766:sulforaphane
Alternative gene promoter; Gene regulation; Human; Microsomal epoxide hydrolase; Nrf2