Caenorhabditis elegans contains structural homologs of human prk and plk

We and others have recently reported cloning and characterization of human prk and plk, members of the polo family of protein serine/threonine kinases that includes the budding yeast cdc5 and Drosophila melanoganster polo. The cdc5 gene is essential for cell cycle progression through mitosis and controls adaptation to the yeast DNA damage checkpoint. Here we report the identification of two new cdc5 homologs from Ceanorhabditis elegans, named plc1 and plc2. The deduced amino acid sequences of Plc1 and Plc2 share strong homology with both human Prk and Plk. plc1 and plc2 genes are closely linked on chromosome III and share 40% residue identity, suggesting that gene duplication followed by independent evolution gives rise to multiple polo homologous genes within a species. Similar to polo family members in other species, two distinct domains are present in Plc1 and Plc2 with the N-terminal half being the putative kinase domain. Interestingly, Plc2, unlike Plc1, contains a less conserved polo box within the C-terminal half of the protein, suggesting a functional division between these two kinases.