Functional Study Of Novel Human Centrosomal Protein Oncogene-cepo

Cepo (centrosomal protein oncogene) is a novel human gene isolated from the cDNA library of fetal liver, highly conserved in evolution, and there is no idea about the function of its homologeous genes among species.The human cepo gene was mapped on 10q24.2 and spanned about 14 kb. The two cDNA isoforms-cepo-A and cepo-B were produced by alternative splicing on the 5'-terminus of cepo gene, the size of two cDNA isoforms of cepo was same and was about 1.5kb. The human cepo-A and cepo-B are composed of 4 and 5 exons respectively, the sequences of the intron/exon junctions were all exactly consistent with the typical GT/AG consensus motif of the splice donor and acceptor sites.Cepo is widely expressed and with a feature of housekeeping gene. The two cDNA isoforms-cepo-A and cepo-B code 99 and 142 animo acid polypeptides respectively, a leucine zipper sequence pattern existed in the C-terminus of these two protein isoforms.CEPO was located mainly at cytoplasm and centrosome of cultured cells in the manner of independence of cell cycle.The ectopic overexpression of this gene in NIH3T3 cells could induce centrosome amplification. Subsequently, the ectopic overexpression of CEPO could induce cell transformation malignantly was confirmed by soft agar growth assay and tumofigenesis in nude mice assays. The protein level of CEPO in some malignant tumors is significantly higher than corresponding normal tissues. Taken together, we reveiled that cepo is an oncogene and named it as cepo.We used the full length CEPO-A and CEPO-B as "bait" in a yeast two-hybrid system to screen a human testis cDNA library, and identified several types of clones. The protein-protein interaction between CEPO and KIF3A (kinesin family member 3A), CEPO and JAB1 (c-Jun activating domain-binding protein 1) were confirmed by in vitro and in vivo interaction binding assays. It was further demonstrated that CEPO enhanced AP-1 activity through signal transduction mediated by JAB1.