Rabbit RAG-2 UTRs: characterization of an unusually large 3' untranslated region

We previously characterized the rabbit recombination activating gene-2 (RAG-2) coding region and a portion of the cDNA. Rabbit RAG-2 mRNA, however, was shown to be approximately twice as large as the predominant form expressed in other vertebrate species, suggesting that it contained additional coding and/or untranslated regions (UTR). In this report, we map and sequence the complete 5' and 3' UTRs of the rabbit RAG-2 transcript and identify and sequence the genomic regions from which they are transcribed. The data show that, with the exception of a 300 nucleotide 5' UTR, almost all of the additional sequence belongs to the 3' UTR and that the 3' UTR sequence is transcribed from a single large exon that encodes most of the coding region and all of the 3' UTR. The 3' UTR contains four poly A signal sites, the last of which is closely followed by a GU-rich region. The rabbit 3' UTR has a high level of identity with the homologous region downstream of the human RAG-2 gene but not with the mouse RAG-2 gene. The region of identity extends several hundred nucleotides beyond the transcribed region and terminates in a series of dinucleotide (TG) repeats. The data are discussed in terms of RAG gene and 3' UTR function, regulation, and evolution.