A NOVEL ROLE FOR CDC5P IN DNA-REPLICATION

DNA replication initiates from specific chromosomal sites called origi ns, and in the budding yeast Saccharomyces cerevisiae these sites are occupied by the origin recognition complex (ORC). Dbf4p is proposed to play a role in targeting the G(1)/S kinase Cdc7p to initiation comple xes late in G(1). We report that Dbf4p may also recruit Cdc5p to origi n complexes. Cdc5p is a member of the Polo family of kinases that is r equired for the completion of mitosis, Cdc5p and Cdc7p each interact w ith a distinct domain of Dbf4p. cdc5-1 mutants have a plasmid maintena nce defect that can be suppressed by the addition of multiple origins. cdc5-1 orc2-1 double mutants are synthetically lethal. Levels of Cdc5 p were found to be cell cycle regulated and peaked in G,IM. These resu lts suggest a role for Cdc5p and possibly Polo-like kinases at origin complexes.