title: Regulation of zebrafish CYP3A65 transcription by AHR2.
abstract: CYP3A proteins are the most abundant CYPs in the liver and intestines, and they play a pivotal role in drug metabolism. In mammals, CYP3A genes are induced by various xenobiotics through processes mediated by PXR. We previously identified zebrafish CYP3A65 as a CYP3A ortholog that is constitutively expressed in gastrointestinal tissues, and is upregulated by treatment with dexamethasone, rifampicin or tetrachlorodibenzo-p-dioxin (TCDD). However, the underlying mechanism of TCDD-mediated CYP3A65 transcription is unclear. Here we generated two transgenic zebrafish, Tg(CYP3A65S:EGFP) and Tg(CYP3A65L:EGFP), which contain 2.1 and 5.4 kb 5' flanking sequences, respectively, of the CYP3A65 gene upstream of EGFP. Both transgenic lines express EGFP in larval gastrointestinal tissues in a pattern similar to that of the endogenous CYP3A65 gene. Moreover, EGFP expression can be significantly induced by TCDD exposure during the larval stage. In addition, EGFP expression can be stimulated by kynurenine, a putative AHR ligand produced during tryptophan metabolism. AHRE elements in the upstream regulatory region of the CYP3A65 gene are indispensible for basal and TCDD-induced transcription. Furthermore, the AHR2 DNA and ligand-binding domains are required to mediate effective CYP3A65 transcription. AHRE sequences are present in the promoters of many teleost CYP3 genes, but not of mammalian CYP3 genes, suggesting that AHR/AHR2-mediated transcription is likely a common regulatory mechanism for teleost CYP3 genes. It may also reflect the different environments that terrestrial and aquatic organisms encounter.
authors.affiliation: Institute of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan.
authors.forename: Chin-Teng
authors.initials: CT
authors.lastname: Chang
authors.forename: Hsin-Yu
authors.initials: HY
authors.lastname: Chung
authors.forename: Hsiao-Ting
authors.initials: HT
authors.lastname: Su
authors.forename: Hua-Pin
authors.initials: HP
authors.lastname: Tseng
authors.forename: Wen-Shyong
authors.initials: WS
authors.lastname: Tzou
authors.forename: Chin-Hwa
authors.initials: CH
authors.lastname: Hu
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D049452:Green Fluorescent Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D017404:In Situ Hybridization, Fluorescence; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism / Q000502:physiology; D010089:Oxidoreductases, N-Demethylating / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D018336:Receptors, Aryl Hydrocarbon / Q000235:genetics* / Q000378:metabolism; D015027:Zebrafish / Q000235:genetics* / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000096:biosynthesis* / Q000235:genetics* / Q000378:metabolism
chemical_list: C474372:AHR2 protein, zebrafish; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D029961:Zebrafish Proteins; D049452:Green Fluorescent Proteins; D001189:Aryl Hydrocarbon Hydroxylases; C502466:cytochrome P-450 CYP3A65, zebrafish; D010089:Oxidoreductases, N-Demethylating