DNA replication licensing factor, required for pre-replication complex assembly. Faithful duplication of the genetic material requires 'once per cell cycle' DNA replication initiation and elongation. Central to this control is the tightly regulated formation of prereplicative complexes (preRCs) at future origins of DNA replication. Required for the recruitment of the MCM helicase complex to the replication origins. Interacts with cdc18. Present in the nucleus after mitosis when DNA licensing takes place. Ubiquitinated by the DCX(DTL) complex, also named CRL4(CDT2) complex, leading to its degradation. Belongs to the Cdt1 family.