Involved in regulation of DNA replication. Stimulates the helicase activity of MCM via stimulation of its ATPase activity. Binding to MCM may result in conformational changes in MCM, leading to catalytic ATP hydrolysis by the helicase. Directly stimulates MCM movement along single-stranded and double-stranded DNA. Does not bind DNA. Interacts with MCM. The N-terminal AAA+ ATPase domain and the C-terminal winged-helix (WH) domain are both required for stimulation of MCM activity. Belongs to the CDC6/cdc18 family.