Cloning of a thyroid hormone-responsive Rana catesbeiana c-erbA-beta gene.

Two types of thyroid hormone receptor (c-erbA) gene have been identified in mammals and in lower species including chickens and the amphibian Xenopus laevis. The two genes are located on different chromosomes and have been named TR alpha and TR beta. We have described previously the cloning of a TR alpha cDNA from Rana catesbeiana (RC) tissues (RC15) and we now report the cloning of a TR beta cDNA from this species. The cloning strategy employed utilized the polymerase chain reaction (PCR), with primers based on the sequences of the X. laevis TR beta cDNA (XenTR beta) and an RCTR beta genomic clone, which, by analogy with XenTR beta, contains some of the 3' end of the open reading frame together with 3'-untranslated sequences. At the nucleotide and amino acid levels, respectively, the cloned RCTR beta cDNA is 90% and 98% homologous with XenTR beta, and 72% and 76% homologous with RC15. Following in vitro transcription and translation, the cDNA was shown to encode a 48 kilodalton protein which binds 3,5,3'-triiodothyronine (T3) with high affinity (mean Kd: 0.032 nM). Samples of total or poly(A) +RNA from tadpoles at different stages of metamorphosis and from adult frogs were analyzed for the presence of TR beta-specific transcripts by slot blot analysis using as probe a 258 bp section of the RCTR beta cDNA. This section of the cDNA does not hybridize to the corresponding section of RC15. In confirmation of previous findings, beta-specific transcripts were not detected in RNA from tadpole red blood cells (RBCs) and none was found in RBCs from adult frogs.(ABSTRACT TRUNCATED AT 250 WORDS)