Physical map of the human immunoglobulin K locus and its implication for the mechanisms of V sub(K)-J sub(K) rearrangement

Genomic regions containing numerous cloned V sub(K) genes were investigated by pulsed-field gel electrophoresis. 31 and 32 genes were linked within 1.0 and 1.3 Mb NotI fragments, respectively; the latter fragment includes also the J sub(K)C sub(K) gene segment. A 0.25 Mb NotI fragment comprises further 10 V sub(K) genes. Since the transcriptional polarities of the V sub(K) genes within the genomic regions are known the linking of the regions allows the authors now to answer unequivocally some longstanding questions concerning the mechanism of V sub(K)-J sub(k) rearrangement. The V sub(K) genes of the 1.3 Mb NoTI fragment except for the two J sub(K) proximal ones are arranged in the same transcriptional polarity as J sub(K)C sub(K) and therefore must rearrange by a deletion mechanism.