Figure 6.

Collaboration of cyclin E/cdk2 with E2F in the induction of S phase. The figure depicts the interaction of the multisubunit complex known as ORC with a DNA replication origin. In addition to the Orc1 protein, the accumulation of additional components of the initiation complex, including each of the Mcms and Cdc6, depends on E2F activity. It is proposed that either the assembly of these components into a functional complex or the activation of an assembled complex is facilitated by cyclin E/cdk2-mediated phosphorylation, thereby triggering origin firing and the initiation of DNA replication.