Vβ cluster sequences reduce the frequency of primary Vβ2 and Vβ14 rearrangements

T-cell receptor (TCR) beta variable region exons are assembled from numerous gene segments in a highly ordered and regulated manner. To elucidate mechanisms and identify cisacting elements that control V beta rearrangement, we generated an endogenous TCR-beta allele with only the V beta 2, V beta 4, and V beta 14 segments. We found that alpha beta T lineage cells containing this V beta(2-4-14) allele and a wild-type TCR-beta allele developed normally, but exhibited a significant increase in V beta 2(+) and V beta 14(+) cells. To quantify V beta rearrangements on the V beta(2-4-14) allele, we generated alpha beta T-cell hybridomas and analyzed TCR-beta rearrangements. Despite the deletion of almost all V beta segments and 234kb of V beta cluster sequences, the V beta(2-4-14) allele exhibited only a slight decrease in V beta rearrangement as compared with the wild-type TCR-beta allele. Thus, cis-acting control elements essential for directing V beta rearrangement across large chromosomal distances are not located within the V beta cluster. We also found a significant increase in the frequency of V beta rearrangements involving V beta 2 and V beta 14, but not V beta 4, on the V beta(2-4-14) allele. Collectively, our data suggest that V beta cluster sequences reduce the frequency of V beta 2 and V beta 14 rearrangements by competing with the productive coupling of accessible V beta 2 and V beta 14 segments with DJ beta 1 complexes.