Transposed human immunoglobulin V kappa gene regions carry clusters of conserved sequence elements

The V kappa I gene regions which have been transposed in evolution from the site of the kappa locus on chromosome 2 to chromosomes 1, 22, and other chromosomes, are very similar and may have been derived from one ancestor gene. Upstream from the transposed genes (called orphons) two types of conserved sequence elements were found using a mouse cell assay system. One type is homologous to the murine sequences which were previously thought to be ARS elements; the other one is related to the binding site of the replication/transcription factor NFIII. Such a combination of elements was seen neither in hybridization experiments with the 1 Mb of the kappa locus available on cosmid clones nor in a computer-aided search of sequence data libraries. We speculate that in the evolutionary past, the clustered elements played a role in the transposition of the V kappa genes, perhaps by causing an over-replication and/or by facilitating the integration of the genes.