DNA segment containing C beta 1, a gene for the constant region of the beta chain of the T-cell antigen receptor, was inserted into chromosome 6 in cells from one patient with human T-cell leukemia.

DNA rearrangements that occurred in the vicinity of T-cell antigen receptor beta-chain gene clusters residing on chromosome 7 were examined in human T-cell acute lymphoblastic leukemia cells. In one patient, it was observed that, for the T-cell receptor beta-chain genes, a D beta 1-J beta 2.3 (where D is diversity and J is joining) junction was found on one chromosome, while the other chromosome kept the germ-line configuration. If this D beta-J beta junction was formed by the customary deletion mechanism, the C beta 1 gene (where C is constant) located between the D beta 1 and J beta 2.3 loci should have disappeared from this chromosome. The C beta 1 gene indeed was absent from the rearranged chromosome 7, but it was found on chromosome 6 as an inserted segment. The implications of the observations are discussed.