1. The Wellcome Trust and Cancer Research UK Gurdon Institute, and Department of Zoology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK
2. Centro Andaluz de Biología Molecular y Medicina Regenerativa CABIMER, Universidad de Sevilla-CSIC, Avenida Américo Vespucio s/n, 41092 Sevilla, Spain
3. Present address: Institute of Molecular Cancer Research, University of Zurich-Irchel, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.

Correspondence to: Stephen P. Jackson¹ Correspondence and requests for materials should be addressed to S.P.J. (Email: s.jackson@gurdon.cam.ac.uk).

Abstract

DNA double-strand breaks (DSBs) are repaired by two principal mechanisms: non-homologous end-joining (NHEJ) and homologous recombination (HR)¹. HR is the most accurate DSB repair mechanism but is generally restricted to the S and G2 phases of the cell cycle, when DNA has been replicated and a sister chromatid is available as a repair template^{2, 3, 4, 5}. By contrast, NHEJ operates throughout the cell cycle but assumes most importance in G1 (refs 4, 6). The choice between repair pathways is governed by cyclin-dependent protein kinases (CDKs)^{2, 3, 5, 7}, with a major site of control being at the level of DSB resection, an event that is necessary for HR but not NHEJ, and which takes place most effectively in S and G2 (refs 2, 5). Here we establish that cell-cycle control of DSB resection in Saccharomyces cerevisiae results from the phosphorylation by CDK of an evolutionarily conserved motif in the Sae2 protein. We show that mutating Ser 267 of Sae2 to a non-phosphorylatable residue causes phenotypes comparable to those of a sae2 null mutant, including hypersensitivity to camptothecin, defective sporulation, reduced hairpin-induced recombination, severely impaired DNA-end processing and faulty assembly and disassembly of HR factors. Furthermore, a Sae2 mutation that mimics constitutive Ser 267 phosphorylation complements these phenotypes and overcomes the necessity of CDK activity for DSB resection. The Sae2 mutations also cause cell-cycle-stage specific hypersensitivity to DNA damage and affect the balance between HR and NHEJ. These findings therefore provide a mechanistic basis for cell-cycle control of DSB repair and highlight the importance of regulating DSB resection.

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.