Human CDT1 Associates with CDC7 and Recruits CDC45 to Chromatin during S Phase

The initiation of DNA replication is a tightly controlled process that involves the formation of distinct complexes at origins of DNA replication at specific periods of the cell cycle. Pre-replicative complexes are formed during telophase and early G(1). They rearrange at the start of S phase to form pre-initiation complexes, which are a prerequisite for DNA replication. The CDT1 protein is required for the formation of the pre-replicative complexes. Here we show that human CDT1 associates with the CDC7 kinase and recruits CDC45 to chromatin. Moreover, we show that the amount of CDT1 bound to chromatin is regulated by CDC7. We propose a model in which chromatin-bound CDT1 is first stabilized and subsequently displaced by CDC7 activity, thereby ensuring the timely execution of DNA replication.