The Zebrafish (Danio rerio) Aryl Hydrocarbon Receptor Type 1 Is a Novel Vertebrate Receptor
- Eric A. Andreasen1,
- Mark E. Hahn3,
- Warren Heideman1,2,
- Richard E. Peterson1,2 and
- Robert L. Tanguay4
- 1Environmental Toxicology Center (E.A.A., W.H., R.E.P.) and 2School of Pharmacy (W.H., R.E.P.), University of Wisconsin, Madison, Wisconsin; 3Biology Department (M.E.H.), Woods Hole Oceanographic Institution, Woods Hole, Massachusetts; and 4Department of Pharmaceutical Sciences (R.L.T.), School of Pharmacy, University of Colorado Health Sciences Center, Denver, Colorado
- Dr. Robert L. Tanguay, Assistant Professor of Molecular Toxicology, University of Colorado Health Sciences Center (UCHSC), Department of Pharmaceutical Sciences, C-238, 4200 East Ninth Avenue, Denver, CO 80262. E-mail:robert.tanguay{at}uchsc.edu
Abstract
Fish are known to have two distinct classes of aryl hydrocarbon receptors, and their roles in mediating xenobiotic toxicity remain unclear. In this study, we have identified and characterized a cDNA tentatively named zebrafish AHR1 (zfAHR1). Analysis of the deduced amino acid sequence reveals that the protein is distinct from zfAHR2 and is more closely related to the mammalian aryl hydrocarbon receptor (AHR). zfAHR1 and zfAHR2 share 40% amino acid identity overall and 58% in the N-terminal half. The zfAHR1 gene maps to linkage group 16 in a region that shares conserved synteny with human chromosome 7 containing the humanAHR, suggesting that the zfAHR1 is the ortholog of the human AHR. zfAHR2 maps to a separate linkage group (LG22). Both zfAHR mRNAs are expressed in early development, but they are differentially expressed in adult tissues. zfAHR2 can dimerize with zfARNT2b and binds with specificity to dioxin-responsive elements (DREs). Under identical conditions, zfAHR1/zfARNT2b/DRE complexes are formed; however, the interactions are considerably weaker. In COS-7 cells expressing zfARNT2b and zfAHR2, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure leads to a significant induction of dioxin-responsive reporter genes. In identical experiments, TCDD exposure fails to induce the reporter gene in zfAHR1-expressing cells. Ligand-binding experiments suggested that the differential zfAHR activities are attributable to differences in TCDD binding because only zfAHR2 exhibits high-affinity binding to [3H]TCDD or β-naphthoflavone. Finally, using chimeric zfAHR1/zfAHR2 constructs, the lack of TCDD-mediated transcriptional activity was localized to the ligand-binding and C-terminal domains of zfAHR1.
Footnotes
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This work was supported in part by National Institute of Environmental Health Sciences grants ES10820 (to R.L.T.) and ES06272 (to M.E.H.), by National Institute of Environmental Health Sciences Developmental and Molecular Toxicology Center grant P30-ES09090 (to W.H. and R.E.P.), and by the University of Wisconsin Sea Grant Institute under grants from the National Sea Grant College Program, National Oceanic and Atmospheric Administration, United States Department of Commerce, Sea Grant Projects R/BT12 and R/BT 14 (to W.H. and R.E.P.). This is contribution 340 of the University of Wisconsin Environmental Toxicology Center and contribution 10,571 from the Woods Hole Oceanographic Institution.
- Abbreviations:
- AHR
- aryl hydrocarbon receptor
- PAS
- PER/ARNT/SIM (period/aryl hydrocarbon receptor nuclear translocator/single-minded)
- ARNT
- aryl hydrocarbon nuclear translocator
- HSP90
- 90-kDa heat shock protein
- AIP
- aryl hydrocarbon interacting protein
- TCDD
- 2,3,7,8-tetrachlorodibenzo-p-dioxin
- DRE
- dioxin-responsive element
- bHLH
- basic helix loop helix
- LBD
- ligand-binding domain
- NLS
- nuclear localization
- NES
- nuclear export
- TBDD
- 2,3,7,8-tetrabromodibenzo-p-dioxin
- PCB126
- 3,3′,4,4′,5-pentachlorobiphenyl
- TCDF
- 2,3,7,8-tetrachlorodibenzofuran
- PeCDF
- 2,3,4,7,8-pentachlorodibenzofuran
- BaP
- benzo[a]pyrene
- I3C
- indole-3-carbinol
- 3MC
- 3-methylcholanthrene
- I3AA
- indole-3-acetic acid
- DMBA
- 7,12-dimethylbenz[a]anthracene
- BNF
- β-naphthoflavone
- PC
- phosphatidylcholine
- PCR
- polymerase chain reaction
- hpf
- hours postfertilization
- TNT
- transcription and translation
- MOPS
- 4-morpholinepropanesulfonic acid
- PAGE
- polyacrylamide gel electrophoresis
- DTT
- dithiothreitol
- TBS-T
- Tris-buffered saline-Tween 20
- DMSO
- dimethyl sulfoxide
- ANOVA
- analysis of variance
- zf
- zebrafish
- AHRR
- aryl hydrocarbon receptor repressor
- RACE
- rapid amplification of cDNA ends
- CMV
- cytomegalovirus
- kb
- kilobase(s)
- Fh
- F. heteroclitus.
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- Received January 16, 2002.
- Accepted April 12, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
