Schematic illustration of the structure of MCM2 and its functions in the cytoplasm and nucleus.

<p>(<b>A</b>) The various functional domains of the MCM2 protein are shown, and the domains and regions required for the activities are indicated. (<b>B</b>) Schematic of the novel role of MCM2 in apoptosis enhancement. Normally, MCM2 is recruited into the nucleus for participation in DNA replication. As a result, cellular proliferation is upregulated (proliferation signal). However, when gp70 is present in the cytoplasm, it binds to MCM2 and inhibits its nuclear entry. Furthermore, cytoplasmic gp70-MCM2-complex interacts with PP2A and inhibits its interaction with DNA-PK. Consequently, hyperphosphorylated DNA-PK enhances DNA-damage-induced apoptosis via a P53-related pathway (apoptosis signal).