Cell cycle regulation of DNA double-strand break end resection by Cdk1 -dependent Dna2 phosphorylation

Resection of DNA 5′ ends is the initial step for repair of double-strand breaks via homologous recombination. DNA resection is controlled in a cell-cycle dependent manner, with yeast Cdk1 known to control Sae2, a nuclease that initiates resection. Now recruitment to DNA damage sites of Dna2, a nuclease responsible for extensive resection, is also shown to be controlled by Cdk1. DNA recombination pathways are regulated by the cell cycle to coordinate with replication. Cyclin-dependent kinase (Cdk1) promotes efficient 5′ strand resection at DNA double-strand breaks (DSBs), the initial step of homologous recombination and damage checkpoint activation. The Mre11–Rad50–Xrs2 complex with Sae2 initiates resection, whereas two nucleases, Exo1 and Dna2, and the DNA helicase–topoisomerase complex Sgs1–Top3–Rmi1 generate longer ssDNA at DSBs. Using Saccharomyces cerevisiae , we provide evidence for Cdk1-dependent phosphorylation of the resection nuclease Dna2 at Thr4, Ser17 and Ser237 that stimulates its recruitment to DSBs, resection and subsequent Mec1-dependent phosphorylation. Poorly recruited dna2 T4A S17A S237A and dna2ΔN248 mutant proteins promote resection only in the presence of Exo1, suggesting cross-talk between Dna2- and Exo1-dependent resection pathways.