Genomic organization of the chicken T-cell receptor beta chain D-J-C region

We examined overlapping genomic clones containing the chicken T cell receptor (TCR) Dbeta-Jbeta-Cbeta complex, which contains a single diversity segment, four joining segments and four exons that encode the constant region. This sequence comprised 18.3 kb. All four Jbeta sequences possessed typical recombination signal sequences (RSS) with intervening 12-bp spacers at their 5'-ends and splice sites at their 3'-ends. No Jbeta-pseudogenes were identified. TGTG sequences in the RSS heptamer sequences were well conserved, as is the case in mammals. A chicken repeat 1-like sequence was found in the intron region between Jbeta-1336 and Cbeta, and several small repeat sequences were identified in intron regions throughout this cloned genome. As germline sequences revealed complete Jbeta sequences, the CDR3 (complementarity-determining region) sequences of TCRbeta from non-immunized splenocytes were analyzed. Non-coding (N) and palindromic (P) nucleotides were frequently observed at the Dbeta-Jbeta recombination sites. There were differences in length of deletion at the 5'-end of each Jbeta. Deletion of the 5'-end of Jbeta-1280 was particularly short when compared with that of Jbeta-1336, but there were no changes in the length of the CDR3 using any of the four Jbeta sequences.