Expression and genomic organization of the zebrafish chaperonin gene complex

Chaperonin 10 and chaperonin 60 monomers exist within the multimeric mitochondrial chaperonin folding complex with a stoichiometry of 2:1. This complex is located in the mitochondrial matrix, where it aids in the folding and acquisition of the tertiary structure of proteins. We have previously isolated the cpn10 cDNA in zebrafish (Danio rerio), and demonstrated that it is ubiquitously expressed during embryonic development and transcriptionally upregulated after exposure to heat shock. In the present study, we have isolated a cDNA encoding chaperonin 60 (cpn60) from zebrafish, and have shown that it is similarly expressed uniformly and ubiquitously throughout early embryonic development of zebrafish. Upregulation of cpn60 expression was also observed after exposure of zebrafish embryos to a heat shock of 1 h at 37 degrees C compared with control embryos raised at 27 degrees C. The induction of the cpn60 heat shock response was greatest after 1 h of heat shock, whereas significant decreases of cpn60 mRNA were observed within 2 h following a return to 27 degrees C. We subsequently isolated genomic DNA sequences for both of these genes, and show that they are also arranged in a head-to-head organization and share a common bidirectional promoter that contains a single heat shock element (HSE). Our database analysis shows that this head-to-head organization is also found in human (Homo sapiens), rat (Rattus norvegicus), pufferfish (Fugu rubripes), and Caenorhabditis elegans, but not in Drosophila or yeast (Saccharomyces cerevisiae). The data suggest that the genomic organization of the cpn gene complex has been conserved across the vertebrates.