Involved in regulation of DNA replication. May play essential roles in origin recognition and cell cycle control of replication. Binds to DNA, with a preference for molecules that contain a bubble, a fork, or a tail. Inhibits the binding of the MCM helicase to the origin DNA and inhibits its DNA helicase activity. Also regulates the DNA polymerase and the nuclease activities of PolB1. Inhibits the DNA-binding activity of Cdc6-1 and Cdc6-2. Monomer. Interacts with Cdc6-1, Cdc6-2, MCM and PolB1. (Microbial infection) At least 4-fold induced following infection by Sulfolobus turreted icosahedral virus 1 (STIV-1) in strain 2-2-12. Strain 2-2-12 is a substrain of P2 that is highly susceptible to infection by Sulfolobus turreted icosahedral virus 1 (STIV-1). Belongs to the CDC6/cdc18 family.