ZFIN ID: ZDB-PUB-050727-18
AHR1B, a new functional aryl hydrocarbon receptor in zebrafish: tandem arrangement of ahr1b and ahr2 genes
Karchner, S.I., Franks, D.G., and Hahn, M.E.
Date: 2005
Source: The Biochemical journal   392: 153-161 (Journal)
Registered Authors: Hahn, Mark E.
Keywords: none
MeSH Terms:
  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Chlorocebus aethiops
  • Conserved Sequence
  • Gene Expression Regulation, Developmental
  • Gene Order/genetics*
  • Molecular Sequence Data
  • Phylogeny
  • Protein Binding
  • Receptors, Aryl Hydrocarbon/chemistry
  • Receptors, Aryl Hydrocarbon/genetics*
  • Receptors, Aryl Hydrocarbon/metabolism*
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Transcription, Genetic
  • Zebrafish*
  • Zebrafish Proteins/chemistry
  • Zebrafish Proteins/genetics*
  • Zebrafish Proteins/metabolism*
PubMed: 16042621 Full text @ Biochem. J.
The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that regulates gene expression following activation by TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) or a variety of other synthetic and natural compounds. Previous studies have identified two AHR genes, AHR1 and AHR2, in zebrafish (Danio rerio), a widely used model species for studying vertebrate development and an emerging model in developmental toxicology. Zebrafish AHR2 binds TCDD with high affinity, is transcriptionally active, and has a major role in mediating the developmental toxicity of TCDD. Zebrafish AHR1 lacks the ability to bind TCDD and activate transcription, and has no known function. Here we report a new zebrafish AHR, designated AHR1B, which shares 34% amino acid sequence identity with AHR1 (AHR1A). The ahr1b gene resides on chromosome 22, adjacent to ahr2, whereas the ahr1a gene is located on chromosome 16. AHR1B is expressed in embryos as early as 24 hours post fertilization and increases through the next two days, but expression is not inducible by TCDD. In contrast to the previously identified AHR1A, in vitro-expressed AHR1B protein exhibits specific, high-affinity binding of [ 3H]TCDD. Furthermore, AHR1B is able to activate transcription of a reporter gene under the control of AHR response elements with an efficacy comparable to that of AHR2, but with a higher EC 50. We speculate that AHR1B may have a physiological role, such as in embryonic development, whereas AHR2 mediates the response to xenobiotics.