The MCM (Mini-Chromosome Maintenance) complex is a key component of the pre-replication complex involved in replication licensing which restricts DNA replication to only once per cell cycle. The MCM complex is a heterohexamer of MCM2, MCM3, MCM4, MCM5, MCM6, and MCM7. MCM4 is part of the core MCM complex that includes MCM4, MCM6, and MCM7. The core complex possesses DNA helicase activity. MCM4 is phosphorylated by CDC2 kinase resulting in a reduction of helicase activity and chromatin binding.