Immunoglobulin JH rearrangement in a T-cell line reflects fusion to the DH locus at a sequence lacking the nonamer recognition signal

Rearrangements of the immunoglobulin heavy chain joining region (J_H) genes occur in some T lymphocytes, probably because the mechanism for assembly of T-cell receptor encoded genes is very similar to that for immunoglobulins. Two such rearrangements described previously represented proper fusion of a D_H and J_H gene. We have cloned and analyzed the J_H rearrangements found on both alleles in the T lymphoma ST4. One represents conventional recombination between a member of the SP2 D_H family and J_H3. On the other allele, J_H4 has recombined with a sequence within the D_H locus but not at a D_H gene. This recombination involved the heptamer but not the nonamer of the bipartite recognition signal required for D_H-J_H joining. This result suggests that the heptamer may be the primary determinant of the specificity in V-gene assembly and that the D_H locus as a whole may be a preferred target for recombination.