CLONING, STRUCTURE AND MESSENGER-RNA EXPRESSION OF HUMAN CCTG, WHICH ENCODES THE CHAPERONIN SUBUNIT CCT-GAMMA

We describe the cloning, DNA sequence analysis and mRNA expression ana lysis of human Cctg (HsCctg), a gene that encodes the gamma-subunit of the eukaryotic cytosolic 'chaperonin-containing TCP-1' (CCT). Partial clones representing the 3' region of HsCctg cDNA were isolated from a human kidney cDNA library, and the missing 5' region was amplified di rectly from human kidney cDNA. The Cctg mRNA transcript is expressed i n numerous human and mouse tissues and, like Tcp-1/Ccta, Cctg mRNA is expressed at higher levels in mouse testis when compared with kidney a nd brain. Southern-blot analysis has also revealed the Cctg gene to be highly conserved in mouse, rat, sheep and frog. The 1901 bp HsCctg cD NA has a coding region of 1635 bp and encodes a predicted 60 kDa prote in (544 amino acids). The predicted HsCCT gamma amino acid sequence sh ares a high degree of sequence similarity with gamma-subunits from the mouse Mus musculus (98% similarity), the yeast Saccharomyces cerevisi ae (75% similarity) and the protozoan Tetrahymena pyriformis (76% simi larity) as well as with other members of the TF55/TCP-1 family, such a s human TCP-1/CCT alpha (55% similarity) and TCP-20/CCT zeta (54% simi larity). HsCCT gamma also shares conserved domains previously identifi ed in the TF55/TCP-1 family of chaperonins and more distantly related chaperonins such as GroEL and Hsp60.