Characterization of Ceap-11 and Ceap-16, Two Novel Splicing–Variant–Proteins, Associated with Centrosome, Microtubule Aggregation and Cell Proliferation

A novel human gene, encoding two polypeptide-isoforms, has been identified from human fetal liver cDNA library. These two alternatively spliced polypeptide-variants are associated with centrosomes, and are designated Ceap-11 and Ceap-16, respectively, according to the acronym Ceap for centrosomal-associated protein and the approximate relative molecular mass. The high degree of sequence similarity between Ceap proteins of divergent species indicates that the Ceap homologous genes are significantly conserved in evolution and constitute a new gene family without any functional information until now. Human Ceap gene is mapped on 10q24.2. These two Ceap cDNA isoforms are generated by RNA alternative splicing on the 5′ terminus of the Ceap gene, and are composed of four and five exons, respectively. Ceap-11 and Ceap-16 are co-immunoprecipitated and co-located with γ-tubulin; ectopic overexpression of these two proteins in NIH3T3 cells induces microtubule aggregation and cell proliferation; the protein level of Ceap in certain tumors is significantly higher than that in corresponding normal tissues. Taken together, our data provide the first evidence for the function of Ceap-11 and Ceap-16, the two novel human proteins, namely, association with centrosome, microtubule aggregation and cell proliferation.