Session: S13-Evolution of Nuclear Receptors
Room 256 (Moscone Center)
We are focused on understanding the diversity and function of nuclear receptors in non-bilaterian animals both to gain insight into the origins of nuclear receptor signaling and to understand how nuclear receptors have diverged within these animal lineages. Arguably the most ancient nuclear receptor, HNF4 is present in all non-bilaterian animal phyla. Two HNF4 genes are the only nuclear receptors present in comb jellies (ctenophores), but surprisingly these genes lack a DNA-binding domain. In sea anemones (cnidarians), HNF4 can activate a DR1-driven reporter in the presence of the co-activator PGC-1. A second ancient nuclear receptor, RXR, is present in placozoans and some cnidarians, and RXR isolated from these organisms bind 9-cis-retinoic acid in vitro, as do the vertebrate homologs. While the functions of nuclear receptors in non-bilaterian animals are not known, studies with protein-binding microarrays indicate that some receptors share remarkably similar DNA-binding specificity with their mammalian homologs.