Short-range linkage relationships, genomic organisation and sequence comparisons of a cluster of five HSP70 genes in Fugu rubripes

Twelve cosmids containing sequences resembling genes encoding members of th e 70-kDa heat-shock protein family, HSP70, have been isolated from Fugu rub ripes. They can be broadly divided into three groups Of overlapping cosmids . Restriction analysis and sequencing of one set of five cosmids have revea led five intronless Fugu HSP70 genes spanning 42 kb, arranged in a combined head-to-head, tail-to-tail and head-to-tail orientation. The levels of DNA and amino acid identity are very high with respect to one another, and are most similar to HSP70 sequences linked to the major histocompatibility com plex (MHC) region in other species. Putative heat-shock consensus elements are identified. Non-HSP70 sequences with homology to known genes have been found physically linked to this Fugu HSP70 cluster: the Drosophila melanoga ster SOL gene, the Drosophila melanogaster nemo gene, the Caenorhabditis el egans T17E9.1 gene and the sequence encoding the serine protease domain. Th e linkage relationships described here so far bear no resemblance to those of HSP70 in other organisms. Convergence of mammalian HSP70 and MHC class I and II loci probably occurred after fish had diverged.