Involved in regulation of DNA replication. May play essential roles in origin recognition and cell cycle control of replication. Binds both single-stranded and double-stranded DNA, with a preference for molecules that contain a bubble, a fork, or a tail. Has a weak ATPase activity. Stimulates the binding of the MCM helicase to the origin DNA, but strongly inhibits ATPase and DNA helicase activities of MCM. Also regulates the DNA polymerase and the nuclease activities of PolB1. Monomer. Interacts with Cdc6-3, MCM and PolB1. The C-terminal WH domain is essential for its stimulating effect on the MCM-loading activity. Autophosphorylated in vitro. Belongs to the CDC6/cdc18 family.