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

DNA recombination pathways are cell cycle regulated 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 crosstalk between Dna2- and Exo1-dependent resection pathways.