Dioxin activation of CYP1A5 promoter/enhancer regions from two avian species, common cormorant (Phalacrocorax carbo) and chicken (Gallus gallus): Association with aryl hydrocarbon receptor 1 and 2 isoforms

Journal Article · Thu Jan 01 04:00:00 EST 2009 · Toxicology and Applied Pharmacology

DOI:https://doi.org/10.1016/j.taap.2008.09.007· OSTI ID:21182686

Lee, Jin-Seon ^[1]; Kim, Eun-Young ^[1]; Iwata, Hisato ^[1]

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1. Center for Marine Environmental Studies (CMES), Ehime University, Bunkyo-cho 2-5, Matsuyama 790-8577 (Japan)

The present study focuses on the molecular mechanism and interspecies differences in susceptibility of avian aryl hydrocarbon receptor (AHR)-cytochrome P4501A (CYP1A) signaling pathway. By the cloning of 5'-flanking regions of CYP1A5 gene from common cormorant (Phalacrocorax carbo) and chicken (Gallus gallus), seven putative xenobiotic response elements (XREs) were identified within 2.7 kb upstream region of common cormorant CYP1A5 (ccCYP1A5), and six XREs were found within 0.9 kb of chicken CYP1A5 (ckCYP1A5). Analysis of sequential deletion and mutagenesis of the binding sites in avian CYP1A5 genes by in vitro reporter gene assays revealed that two XREs at -613 bp and -1585 bp in ccCYP1A5, and one XRE at -262 bp in ckCYP1A5 conferred TCDD-responsiveness. The binding of AHR1 with AHR nuclear translocator 1 (ARNT1) to the functional XRE in a TCDD-dependent manner was verified with gel shift assays, suggesting that avian CYP1A5 is induced by TCDD through AHR1/ARNT1 signaling pathway as well as mammalian CYP1A1 but through a distinct pathway from mammalian CYP1A2, an ortholog of the CYP1A5. TCDD-EC{sub 50} for the transcriptional activity in both cormorant AHR1- and AHR2-ccCYP1A5 reporter construct was 10-fold higher than that in chicken AHR1-ckCYP1A5 reporter construct. In contrast, chicken AHR2 showed no TCDD-dependent response. The TCDD-EC{sub 50} for CYP1A5 transactivation was altered by switching AHR1 between the two avian species, irrespective of the species from which the regulatory region of CYP1A5 gene originates. Therefore, the structural difference in AHR, not the CYP1A5 regulatory region may be a major factor to account for the dioxin susceptibility in avian species.

• OSTI ID: 21182686
• Journal Information: Toxicology and Applied Pharmacology, Journal Name: Toxicology and Applied Pharmacology Journal Issue: 1 Vol. 234; ISSN TXAPA9; ISSN 0041-008X
• Country of Publication: United States
• Language: English

Related Subjects

60 APPLIED LIFE SCIENCES
CHICKENS
CLONING
DIOXIN
GELS
GENES
HYDROCARBONS
IN VITRO
MUTAGENESIS
PROMOTERS
RECEPTORS