A lymphocyte-specific enhancer in the mouse immunoglobulin kappa gene.

During differentiation of lymphocytes into antibody-producing cells, an immunoglobulin kappa variable-region gene is transcriptionally activated by rearrangement linking it to a kappa constant (C kappa) region gene which is already transcribed prior to somatic rearrangement. The presence of a transcriptional enhancer element within the large intron of the kappa light-chain gene has been postulated to explain this mode of activation, supported by evidence of a chromatin region which is preferentially accessible to DNase I and restriction enzymes. This DNA region contains a segment of about 130 base pairs (bp) which is strongly conserved between mouse, rabbit and man. Moreover, no transcripts are detectable from a kappa gene, which is truncated within the large intron. Recently, a lymphocyte-specific enhancer has been identified downstream of the joining region in immunoglobulin heavy-chain genes. We now show direct evidence for a functionally similar enhancer within the large kappa gene intron of the mouse. It is, however, less active than the heavy-chain gene enhancer. In contrast, no enhancer was found to be associated with a cloned lambda I light-chain gene.