Structure and rearrangement of the T cell receptor J alpha locus in T cells and leukemic T cell lines

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Abstract
The vast majority of T cells express an antigen receptor (TcR) composed of an α/β heterodimer. The α and β chains are encoded for by a set of variable (V), joining (J) and constant (C) region genes. Unlike the J genes of the β chain which are limited in number and are clustered close to the constant region, the Jα, genes are spread over an 85‐kilobase DNA region, upstream of the C, gene. We have isolated the complete J, locus, bounded on the 5' side by the C sequence of the 6 gene and on the 3' side by the C sequence of the a gene. The experiments described here demonstrate that the J gene segments extend 75 kb 5' of Cα, and participate equally in generating the diversity of the a chain in peripheral T cells. Similarly, in leukemic T cell lines, rearrangements occurred over the entire locus and involved both alleles. Densitometry data suggest that in most peripheral T cells both alleles also are rearranged; thus, allelic exclusion in the α locus does not occur at the level of rearrangement. In three cell lines, an rearrangement has occurred on one allele in a region located 10 kb from the 5' end of the locus.