Processing of homologous recombination repair intermediates by the Sgs1-Top3-Rmi1 and Mus81-Mms4 complexes

Cell Cycle. 2011 Sep 15;10(18):3078-85. doi: 10.4161/cc.10.18.16919. Epub 2011 Sep 15.


Homologous recombination repair (HRR) is an evolutionarily conserved cellular process that is important for the maintenance of genome stability during S phase. Inactivation of the Saccharomyces cerevisiae Sgs1-Top3-Rmi1 complex leads to the accumulation of unprocessed, X-shaped HRR intermediates (X structures) following replicative stress. Further characterization of these X structures may reveal why loss of BLM (the human Sgs1 ortholog) leads to the human cancer predisposition disorder, Bloom syndrome. In two recent complementary studies, we examined the nature of the X structures arising in yeast strains lacking Sgs1, Top3 or Rmi1 by identifying which proteins could process these structures in vivo. We revealed that the unprocessed X structures that accumulate in these strains could be resolved by the ectopic overexpression of two different Holliday junction (HJ) resolvases, and that the endogenous Mus81-Mms4 endonuclease could also remove them, albeit slowly. In this review, we discuss the implications of these results and review the putative roles for the Sgs1-Top3-Rmi1 and Mus81-Mms4 complexes in the processing of various types of HRR intermediates during S phase.

Publication types

  • Review

MeSH terms

  • DNA Breaks, Single-Stranded
  • DNA Replication
  • DNA, Cruciform / genetics
  • DNA, Cruciform / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Endonucleases / genetics
  • Endonucleases / metabolism
  • Holliday Junction Resolvases / genetics
  • Holliday Junction Resolvases / metabolism
  • Humans
  • RecQ Helicases / genetics
  • RecQ Helicases / metabolism
  • Recombinational DNA Repair*
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism


  • DNA, Cruciform
  • DNA-Binding Proteins
  • Rmi1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • TOP3 protein, S cerevisiae
  • Endonucleases
  • MUS81 protein, S cerevisiae
  • MUS81 protein, human
  • Holliday Junction Resolvases
  • Bloom syndrome protein
  • SGS1 protein, S cerevisiae
  • RecQ Helicases