S-CDK-regulated bipartite interaction of Mcm10 with MCM is essential for DNA replication

Mcm10 plays an essential role in the activation of replicative helicase CMG through the cell cycle-regulated interaction with the prototype MCM double hexamer in <i>Saccharomyces cerevisiae</i>. In this study, we reported that Mcm10 is phosphorylated by S-phase cyclin-dependent kinases (S-CDKs) at S66, which enhances Mcm10--MCM association during the S phase. S66A single mutation or even deletion of whole N-terminus (a.a. 1-128) only causes mild growth defects. Nevertheless, S66 becomes indispensable in the absence of the Mcm10 C-terminus ((a.a. 463-571), the major MCM-binding domain. Using a two-degron strategy to efficiently deplete Mcm10, we show that <i>mcm10</i>-S66AΔC has a severe defect in proceeding into the S phase. Notably, both lethality and S-phase deficiency can be rescued by artificially tethering <i>mcm10</i>-S66AΔC to MCM. These findings illustrate how the Mcm10-MCM association is regulated as a crucial event in DNA replication initiation.