Involved in the initiation of DNA replication. Also participates in checkpoint controls that ensure DNA replication is completed before mitosis is initiated. Interacts with PCNA, ORC1, cyclin-CDK (By similarity). Interacts with HUWE1 (By similarity). Interacts with ANKRD17 (By similarity). Interacts with GRWD1; origin binding of GRWD1 is dependent on CDC6 (By similarity). Interacts with CDT1; are mutually dependent on one another for loading MCM complexes onto chromatin (By similarity). Interacts with TTC4 (By similarity). Interacts (via Cy motif) with CCNF; the interaction takes place during G2 and M phase (By similarity). Interacts with CDH1 (By similarity). The protein is nuclear in G1 and cytoplasmic in S-phase cells. Ubiquitinated by the SCF(CCNF) E3 ubiquitin-protein ligase complex. Belongs to the CDC6/cdc18 family. Extended N-terminus. Extended N-terminus.