MCM5 isa protein involved in the initiation of DNA replication. The encoded protein is a member of the MCM family of chromatin-binding proteins and can interact with at least two other members of this family. The encoded protein is upregulated in the transition from the G0 to G1/S phase of the cell cycle and may actively participate in cell cycle regulation.Depletion of ASF1 by RNA interference impeded DNA unwinding at replication sites, and similar defects arose from overproduction of new histone H3-H4 that compromised ASF1 function.ASF1, as a histone acceptor and donor, handles parental and new histones at the replication fork via an ASF1-(H3-H4)-MCM2-7 intermediate and thus provides a means to fine-tune replication fork progression and histone supply and demand.