PW05 Genomics and Proteomics
Exhibit Hall
8:00 AM - Wednesday, 12 November 2003
(PW100) Is it ARNT? Identification of the Aryl Hydrocarbon Receptor Nuclear Translocator from the Clam, Mya arenaria.
Butler, R.1, Tonneson, J.1, Hahn, M.2, Van Beneden, R.1, 1 University of Maine, Orono, ME, USA2 Woods Hole Oceanographic Institution, Woods Hole, MA
ABSTRACT- ARNT (aryl hydrocarbon receptor nuclear translocator) is the dimerization partner for various members of the bHLH/PAS family of transcription factors. These dimers activate diverse pathways involved in neurogenesis, cardiovascular development, angiogenesis, response to hypoxia and regulation of biotransformation enzymes. It is this last function, resulting from the ligand-activated heterodimerization of ARNT with the aryl hydrocarbon receptor (AHR), which has been most extensively studied. Recent work with invertebrate AHRs (M. arenaria, D. melanogaster and C. elegans; Butler et al., 2001, Gene 278:223) demonstrated lack of binding to prototypical ligands, suggesting differences between the vertebrate and invertebrate AHR signaling pathways. To further investigate these differences, the putative clam ARNT was cloned. Currently, four forms of M. arenaria ARNT have been sequenced: 3 of these are complete coding sequences and the last is a partial, missing the 3' end. These sequences code for proteins with estimated sizes of ∼50-73 kDa, with the partial coding ∼43kDa thus far. Phylogenetic analysis clearly supports designation of these sequences as ARNT homologs. We speculate that these forms arose from alternative splicing, as insertions and deletions appear at or near the known mammalian ARNT splice junctions. In clam gonad, one form of ARNT (mRNA) is expressed predominantly. Protein/protein interactions between the various ARNTs and the AHR will be characterized using a yeast two-hybrid system. Although the functional significance of these ARNT variants is not known, the presence of multiple forms may suggest an even more complex regulation by ARNT in the clam than initially anticipated.
Key words: yeast two-hybrid, ARNT, bHLH/PAS, bivalve