14-3-3 proteins function in the initiation and elongation steps of DNA replication in Saccharomyces cerevisiae.

14-3-3s are highly conserved abundant eukaryotic proteins essential for viability, at least in lower eukaryotes. We previously showed that they associate with mammalian and yeast replication origins in a cell-cycle-dependent manner, and are involved in the initiation of DNA replication. Here, we present evidence that 14-3-3 proteins are novel regulators of the initiation and elongation steps of DNA replication in Saccharomyces cerevisiae. The results show that the Bmh2 protein, one of the two 14-3-3 homologues in S. cerevisiae, interacts with Mcm2 and Orc2 proteins, binds to ARS1 maximally at the G1 phase, is essential for plasmid stability, and is required for normal S-phase entry and progression. Furthermore, during G1 phase, the Bmh2 protein is required for the association of MCM proteins with chromatin and their maintenance at replication origins. The results reveal that 14-3-3 proteins function as essential factors for the assembly and maintenance of the pre-replication complex during G1 phase.