Cloning and Sequencing of the Gilthead Sea Bream Estrogen Receptor cDNA

We report here the complete nucleotide sequence of a cDNA clone containing the full-coding sequence of the Sparus aurata estrogen receptor (ER) isolated from an expression library prepared from gilthead sea bream liver poly A+ RNA. The library was screened using a single strand rainbow trout ER cDNA probe, corresponding to the C-D domain. The cDNA sequence containing an insert of 2369 nucleotides was found to encode a protein of 579 amino acids. The 5'- and 3'-untranslated regions of the message are 186 and 392 nucleotides long, respectively. The gilthead sea bream ER shows the higher homology with the ER of another perciform, Chrysophrys major (93%), moderate to high homology with Oreocromis aureus (78%) medaka (77%) and rainbow trout (70.7%) ERs and lower homology with japanese eel (45%), amphibian (47%), avian (48.5%) and mammalian (47-47.5%) ERs. The sequence homologies and phylogenetic analysis of the various ERs suggest that gilthead sea bream ER should be considered as a ER alpha-like.