Cloning, expression and mapping of the full-length cDNA of human CCTβ subunit

Chaperonins assist the proper folding of target proteins without being a part of the substrates. The eukaryotic cytosolic chaperonin, CCT-Chaperonin Containing TCP-1 (tailless complex polypeptide-1), is mainly involved in the formation of cytoskeletal proteins and is essential for cell viability. Mammalian CCT is commonly a protein complex composed of 7–9 subunit species. We have isolated a novel full-length cDNA from human testis cDNA library. This cDNA of 1935 bp contains a 1605 bp open reading frame (ORF) encoding 535 amino acids (aa). The deduced protein of the cDNA is highly homologous to the CCTβ subunit ofsaccharomyces cerevisiae,schizosaccharomyces pombe, caenorhabditis elegans and mouse, etc. Especially high homology (97%) is found between the deduced protein and mouse CCTβ. On the basis of such high homology, the protein encoded by the new gene was proposed to be a human CCTβ subunit. Northern hybridization showed that humanCCTβ gene is expressed as a transcript of about 2.0 kb in various tissues. Overexpression was seen in testis with the expression level 3–24 times of those in other tissues. TheCCTβ gene was mapped to human chromosome 12q14 by Radiation Hybrid Mapping. Through homologous search, the 5′-end of the cDNA sequence was found to share intermittent regional homology with the 3′-end of human genomic sequence (U91327).The genomic structure of the 5′-end ofCCTβ was also described in detail through comparative analysis.