Abnormal recombination products result from aberrant DNA rearrangement of the human T-cell antigen receptor beta-chain gene.

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Abstract
Two unusual rearrangements of the T-cell antigen receptor .beta.-chain gene have occurred in the human T-cell tumor line CEM. The .beta. chain of the T-cell antigen receptor is encoded in germ-line DNA by immunoglobulin-like gene segments that rearrange during the somatic development of T cells to form active genes. Structural analysis of rearranged immunoglobulin genes has already revealed a great deal about the mechanisms by which these genes rearrange. To further characterize the mechanism by which .alpha.-chain genes rearrange, we have determined the organization of the rearranged .beta.-chain gene segments in the human T-cell tumor line CEM. Three rearranged joining (J) or diversity (D) segments of the .beta.-chain gene are found in CEM. One of these segments rearranged during the formation of a normal rearranged .beta.-chain gene that comprises a variable (V.beta.), D.beta., and J.beta. gene segment associated with a constant region gene segment. Two abnormal recombination products are found at the other rearranged .beta.-chain locus. One product has the structure, J.beta.-D.beta.-J.beta., with the K.beta. gene segments joined in a head-to-head fashion, while the other one consists of a V.beta.-D.beta. recombined segment not associated with a J.beta. gene segment. We propose that the J.beta.-D.beta.-J.beta. structure was formed by an inversion of 6 kilobases of DNA and subsequently, a V.beta.-D.beta. rearrangement occurred. The presence of these products in CEM has important implications for our understanding of the mechanism by which somatic rearrangements of .beta.-chain gene segments occur.