MP7 Toxicogenomics in Environmental Studies
Monday, 14 November 2005: 8:00 AM - 5:30 PM in Exhibit Hall
(BUT-1117-803863) Interaction trapping of novel aryl hydrocarbon receptor (AHR) interactors from a Mya arenaria cDNA library.
Butler, R1, Van Beneden, R1, 1 University of Maine, Orono, ME, USA
ABSTRACT- Increasing evidence suggests that the AHR has a role independent of dioxin binding. This is apparent given that invertebrate AHR homologues (M. arenaria, D. melanogaster and C. elegans) lack the ability to bind prototypical ligands ([3H]TCDD and [3H] 
-naphthoflavone). Additionally, AHR is the only member of the PAS superfamily of transcriptional regulators to be ligand activated. Taken together, one might speculate that the invertebrate AHRs may not have the same requirements as vertebrate AHRs for ligand activation. Investigation into the gonadal expression of M. arenaria AHR revealed a positive correlation between AHR protein levels and stage of ovogenesis. To better understand AHR function in the female clam reproductive tissue, a truncated AHR (amino acids 1-400) was used as the 'bait' protein to screen a yeast two-hybrid cDNA expression library prepared from the gonad of a female with mature gametes. Sequence homology analysis revealed an array of putative AHR-interacting proteins. A number of these proteins have been identified by others as essential for early zebrafish, yeast, worm and/or fly development (e.g., ribonucleoside reductase small subunit, ribosomal proteins L7 and L13, nacscent polypeptide-associated complex a subunit and zinc finger 183). Full-length sequences for proteins in this category were obtained by RACE PCR and re-evaluated by interaction trapping. Proteins found positive for interaction with AHR are currently being verified by an independent, in vitro method. We hypothesize that interaction with one or more of these critical developmental genes may indicate an endogenous function for the AHR.
Key words: aryl hydrocarbon receptor, protein-protein interaction, bivalve, TCDD