Mph1 and Mus81-Mms4 prevent aberrant processing of mitotic recombination intermediates

Mol Cell. 2013 Oct 10;52(1):63-74. doi: 10.1016/j.molcel.2013.09.007.


Homology-dependent repair of double-strand breaks (DSBs) from nonsister templates has the potential to generate loss of heterozygosity or genome rearrangements. Here we show that the Saccharomyces cerevisiae Mph1 helicase prevents crossovers between ectopic sequences by removing substrates for Mus81-Mms4 or Rad1-Rad10 cleavage. A role for Yen1 is only apparent in the absence of Mus81. Cells lacking Mph1 and the three nucleases are highly defective in the repair of a single DSB, suggesting that the recombination intermediates that accumulate cannot be processed by the Sgs1-Top3-Rmi1 complex (STR). Consistent with this hypothesis, ectopic joint molecules (JMs) accumulate transiently in the mph1Δ mutant and persistently when Mus81 is eliminated. Furthermore, the ectopic JMs formed in the mus81Δ mutant contain a single Holliday junction (HJ) explaining why STR is unable to process them. We suggest that Mph1 and Mus81-Mms4 recognize an early strand exchange intermediate and direct repair to noncrossover or crossover outcomes, respectively.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • DEAD-box RNA Helicases / genetics
  • DEAD-box RNA Helicases / metabolism*
  • DNA Breaks, Double-Stranded
  • DNA Repair
  • DNA Repair Enzymes / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Endonucleases / genetics
  • Endonucleases / metabolism*
  • Flap Endonucleases / genetics
  • Flap Endonucleases / metabolism*
  • Gene Expression Regulation, Fungal
  • Holliday Junction Resolvases / metabolism
  • Mitosis*
  • Mutation
  • RecQ Helicases / metabolism
  • Recombination, Genetic*
  • Saccharomyces cerevisiae / enzymology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Single-Strand Specific DNA and RNA Endonucleases / metabolism
  • Time Factors


  • DNA-Binding Proteins
  • Saccharomyces cerevisiae Proteins
  • Endonucleases
  • Flap Endonucleases
  • MUS81 protein, S cerevisiae
  • RAD1 protein, S cerevisiae
  • Holliday Junction Resolvases
  • Yen1 protein, S cerevisiae
  • MMS4 protein, S cerevisiae
  • RAD10 protein, S cerevisiae
  • Single-Strand Specific DNA and RNA Endonucleases
  • MPH1 protein, S cerevisiae
  • SGS1 protein, S cerevisiae
  • RecQ Helicases
  • DEAD-box RNA Helicases
  • DNA Repair Enzymes