 It is an essential regulator of DNA replication and plays important roles in the activation and maintenance of the checkpoint mechanisms in the cell cycle that coordinate S phase and mitosis.It is part of the pre-replicative complex (pre-RC) and is required for loading minichromosome maintenance (MCM) proteins onto the DNA, an essential step in the initiation of DNA synthesis.In addition, it is a member of the family of AAA+ ATPases and highly related to ORC1.