The human homolog of Saccharomyces cerevisiaeMcm10 interacts with replication factors and dissociates from nuclease-resistant nuclear structures in G<SUB>2</SUB> phase

Mcm10 (Dna43), first identified in Saccharomyces cerevisiae, is an essential protein which functions in the initiation of DNA synthesis. Mcm10 is a nuclear protein that is localized to replication origins and mediates the interaction of the Mcm2-7 complex with replication origins. We identified and cloned a human cDNA whose product was structurally homologous to the yeast Mcm10 protein. Human Mcm10 (HsMcm10) is a 98-kDa protein of 874 amino acids which shows 23 and 21% overall similarity to Schizosaccharomyces pombeCdc23 and S.cerevisiae Mcm10, respectively. The messenger RNA level of HsMcm10 increased at the G₁/S-boundary when quiescent human NB1-RGB cells were induced to proliferate as is the case of many replication factors. HsMcm10 associated with nuclease-resistant nuclear structures throughout S phase and dissociated from it in G₂ phase. HsMcm10 associated with human Orc2 protein when over­expressed in COS-1 cells. HsMcm10 also interacted with Orc2, Mcm2 and Mcm6 proteins in the yeast two-hybrid system. These results suggest that HsMcm10 may function in DNA replication through the inter­action with Orc and Mcm2-7 complexes.