Isolation and characterization of a genomic fosmid clone containing hspb1 (hsp27) from the Pacific bluefin tuna Thunnus orientalis

We constructed a fosmid library of genomic DNA from the Pacific bluefin tuna Thunnus orientalis and isolated a clone containing the complete gene hspb1 (hsp27) from the library. To screen the library, we first obtained a full-length hspb1 cDNA by RACE-PCR. This cDNA encodes a putative protein of 202 amino acids. Phylogenetic analysis indicated that the protein belongs to the Hsp27 family. Northern blot analysis demonstrated that the gene transcript was expressed in tuna muscle tissues. Using a combination of PCR screening and colony hybridization, we isolated a 39,422-bp fosmid clone containing hspb1 from an arrayed library. Sequence alignment showed that hspb1 contains three exons and two introns. Comparative genomic analysis revealed that hspb1 lies in a region of conserved synteny in the genomes of fish and human. Our finding of conserved regions within and around hspb1 in fish species will help to identify functional elements such as promoter regions.