OLLIKAINEN, N.*; CHANDSAWANGBHUWANA, C.; Univ. of California, San Diego: Evolution of Ecdysone and Thyroid Hormone Receptors

Ecdysone and thyroid hormone are two ligands that have important roles in regulating metamorphosis in animals. Ecdysone is a steroid, that regulates molting in insects. Thyroid hormone is a non-steroidal ligand, that regulates differentiation and development in fish and amphibia. Although ecdysone and thyroid hormone have different chemical structures, both hormones act by binding to receptors, which are transcription factors that belong to the nuclear receptor family. We analyzed the evolution of structure and function in the ecdysone receptor (EcdR) and thyroid hormone receptor (TR) using their sequences from invertebrates and vertebrates that are stored in GenBank and other orthologous sequences of EcdR and TR that we extracted from searches of recently sequenced genomes of amphioxus, anemone, Ciona, hydra and sea urchin. We used bioinformatics programs to construct an ancestral EcdR and TR. The known and ancestral EcdR and TR sequences were mapped onto 3D structures of EcdR and TR in the Protein Data Bank to elucidate the evolution of specific functional sites on these transcription factors.