Human DNA replication factors:new interactions and functional significance

Abstract

The Mini-chromosome maintenance (Mcm) complex is a central component of the DNA unwinding reaction during eukaryotic DNA replication. DNA primase activity is required at the DNA replication fork to synthesize short RNA primers for DNA chain elongation on the lagging strand. Using purified Mcm and DNA polymerase α-primase complexes, we find that both Mcm4/6/7 and Mcm2~7 complex interact with the DNA polymerase α-primase oloenzyme and also with the hetero-dimeric DNA primase composed of the p48 and p58 subunits. Both the Mcm4/6/7 and Mcm2~7 complexes stimulate RNA primer synthesis by DNA primase in vitro. Our findingsindicate that a direct physical interaction between primase and Mcm may facilitate priming reaction. The eukaryotic DNA replication protein Mcm10 associates with chromatin in early S-phase and is required for assembly and function of the replication fork protein machinery. Another essential component of the eukaryotic replication fork is Cdc45, which is required for both initiation and elongation of DNA replication. Here we report for the first time physical and functional interactions of human Mcm10 and Cdc45. We first demonstrated that Mcm10 and Cdc45 interact in vivo and in vitro. We have detected a direct physical interaction between CTD (C-Terminal Domain of Mcm10) while Mcm10 ID (Internal Domain) with Cdc45 takes place only in the presence of DNA. Both ID and CTD show DNA binding capability. Our results demonstrate that human Mcm10 and Cdc45 directly interact and establish a mutual cooperation in DNA binding.