A role for centrin 3 in centrosome reproduction

Centrosome reproduction by duplication is essential for the bipolarity of c ell division, but the molecular basis of this process is still unknown. Mut ations in Saccharomyces cerevisiae CDC31 gene prevent the duplication of th e spindle pole body (SPB). The product of this gene belongs to the calmodul in super-family and is concentrated at the half bridge of the SPB. We prese nt a functional analysis of HsCEN3, a human cen-trin gene closely related t o the CDC31 gene. Transient overexpression of wild-type or mutant forms of HsCen3p in human cells demonstrates that centriole localization depends on a functional fourth EF-hand, but does not produce mitotic phenotype. Howeve r, injection of recombinant HsCen3p or of RNA encoding HsCen3p in one blast omere of two-cell stage Xenopus laevis embryos resulted in undercleavage an d inhibition of centrosome duplication. Furthermore, HsCEN3 does not comple ment mutations or deletion of CDC31 in S. cerevisiae, but specifically bloc ks SPB duplication, indicating that the human protein acts as a dominant ne gative mutant of CDC31. Several lines of evidence indicate that HsCen3p act s by titrating Cdc31p-binding protein(s). Our results demonstrate that, in spite of the large differences in centroso me structure among widely divergent species, the centrosome pathway of repr oduction is conserved.