Allotypes of the constant region of the rabbit T cell receptor beta-2 chain.

Our laboratory previously reported that there was restriction fragment length polymorphism of TCR C beta genes in rabbits. EcoRI digests of DNA from different rabbits gave fragments of 9 and 6 kb (C beta a) or 14 and 6 kb (C beta b) that hybridized to a C beta cDNA probe. We also reported that the 9- and 14-kb types segregated as Mendelian traits and that there were allotypic differences in the first exon of the C beta 1 genes of C beta a and C beta b animals. Here we report the DNA sequence of the C beta 2 gene present in the 6-kb EcoRI fragment from a C beta b animal and compare the exon sequences with that of a cDNA from a C beta a animal. We find replacement changes in the first and third exons that probably represent allotypic forms of the rabbit C beta 2 gene. The genomic DNA 59 of exon 1 of both beta 1 and beta 2 contain alternating purine/pyrimidine repeat sequences. The genomic C beta 2 has an open reading frame of 69 amino acids in frame with exon 1 similar to a longer one previously found 59 of exon 1 of C beta 1. Further 59 of this region, rabbit C beta 1 and C beta 2 DNA sequences are only about 66% similar. Both the C beta 1 and C beta 2 sequences have two chi sequences; one in exon 1 with a perfect match and one in the intron downstream of exon 1 with one mismatch. Alternating purine/pyrimidine repeats and chi sequences found in rabbit C beta 1 and C beta 2 genes may have contributed to process(es) of gene duplication and/or conversion.