Isolation and characterisation of the retinoic acid receptor-alpha gene inthe Japanese pufferfish, F-rubripes

Nuclear hormone receptors (NRs) are ligand-inducible transcription factors that mediate critical functions in many species. The majority of novel NRs have hitherto been cloned from cDNA libraries by virtue of their homology t o previously identified receptors. In this study, we validate a genomic DNA -based approach to isolating NRs by cloning the retinoic acid receptor-alph a (RAR alpha) gene from the genome of the Japanese pufferfish, Fugu rubripe s. The: fRAR alpha gene is more compact than its human and murine counterpa rts and demonstrates a highly conserved genomic organisation and amino acid sequence, generating two isoforms (fRAR alpha 1 and fRAR alpha 2) with div ergent aminoterminal domains. In addition, a conserved regulatory element c ontaining a retinoic acid response element was identified upstream of the f RAR alpha 2-specific exon, implying that retinoid induction of this isoform is evolutionarily conserved and critical to its function in vivo. We propo se two uses for the Fugu genome in the study of NRs: the isolation of novel NRs that exhibit restricted spatio-temporal expression from genomic DNA an d the identification of evolutionarily conserved promoter or intragenic reg ulatory DNA elements. (C) 1999 Elsevier Science B.V. All rights reserved.