Competing Roles of DNA End Resection and Non-Homologous End Joining Functions in the Repair of Replication-Born Double-Strand Breaks by Sister-Chromatid Recombination

Nucleic Acids Res. 2013 Feb 1;41(3):1669-83. doi: 10.1093/nar/gks1274. Epub 2012 Dec 18.

Abstract

While regulating the choice between homologous recombination and non-homologous end joining (NHEJ) as mechanisms of double-strand break (DSB) repair is exerted at several steps, the key step is DNA end resection, which in Saccharomyces cerevisiae is controlled by the MRX complex and the Sgs1 DNA helicase or the Sae2 and Exo1 nucleases. To assay the role of DNA resection in sister-chromatid recombination (SCR) as the major repair mechanism of spontaneous DSBs, we used a circular minichromosome system for the repair of replication-born DSBs by SCR in yeast. We provide evidence that MRX, particularly its Mre11 nuclease activity, and Sae2 are required for SCR-mediated repair of DSBs. The phenotype of nuclease-deficient MRX mutants is suppressed by ablation of Yku70 or overexpression of Exo1, suggesting a competition between NHEJ and resection factors for DNA ends arising during replication. In addition, we observe partially redundant roles for Sgs1 and Exo1 in SCR, with a more prominent role for Sgs1. Using human U2OS cells, we also show that the competitive nature of these reactions is likely evolutionarily conserved. These results further our understanding of the role of DNA resection in repair of replication-born DSBs revealing unanticipated differences between these events and repair of enzymatically induced DSBs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carrier Proteins / antagonists & inhibitors
  • Cell Line, Tumor
  • Chromatids
  • DNA Breaks, Double-Stranded*
  • DNA End-Joining Repair*
  • DNA Replication*
  • DNA-Activated Protein Kinase / antagonists & inhibitors
  • DNA-Binding Proteins / genetics
  • Endodeoxyribonucleases / genetics
  • Endodeoxyribonucleases / metabolism
  • Endonucleases / metabolism
  • Exodeoxyribonucleases / genetics
  • Exodeoxyribonucleases / metabolism
  • Gene Deletion
  • Humans
  • Nuclear Proteins / antagonists & inhibitors
  • RecQ Helicases / metabolism
  • Recombination, Genetic*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism

Substances

  • Carrier Proteins
  • DNA-Binding Proteins
  • Nuclear Proteins
  • SAE2 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • YKU70 protein, S cerevisiae
  • DNA-Activated Protein Kinase
  • Endodeoxyribonucleases
  • Endonucleases
  • Exodeoxyribonucleases
  • MRE11 protein, S cerevisiae
  • RBBP8 protein, human
  • exodeoxyribonuclease I
  • SGS1 protein, S cerevisiae
  • RecQ Helicases