Alternate pathways involving Sgs1/Top3, Mus81/ Mms4, and Srs2 prevent formation of toxic recombination intermediates from single-stranded gaps created by DNA replication.
Toxic recombination events are detected in vegetative Saccharomyces cerevisiae cells through negative growth interactions between certain combinations of mutations. For example, mutations affecting both the Srs2 and Sgs1 helicases result in extremely poor growth, a phenotype suppressed by mutations in genes that govern early stages of recombination. Here, we identify a similar interaction involving double mutations affecting Sgs1 or Top3 and Mus81 or Mms4. We also find that the primary DNA structures that initiate these toxic recombination events cannot be double-strand breaks and thus are likely to be single-stranded DNA. We interpret our results in the context of the idea that replication stalling leaves single-stranded DNA, which can then be processed by two competing mechanisms: recombination and nonrecombination gap-filling. Functions involved in preventing toxic recombination would either avoid replicative defects or act on recombination intermediates. Our results suggest that Srs2 channels recombination intermediates back into the gap-filling route, whereas Sgs1Top3 and Mus81Mms4 are involved in recombination andor in replication to allow replication restart.
Fabre
Francis
F
Unité Mixte de Recherche 217, Centre National de la Recherche Scientifique-Commissariat à l'Energie Atomique. Département de Radiobiologie et Radiopathologie BP6, 92265 Fontenay-aux-Roses, France. fracis.fabre@cea.fr
Chan
Allan
A
Heyer
Wolf-Dietrich
WD
Gangloff
Serge
S
D004265:DNA Helicases / Q000502:physiology*; D004261:DNA Replication; D004264:DNA Topoisomerases, Type I / Q000502:physiology*; D004271:DNA, Fungal / Q000737:chemistry*; D004268:DNA-Binding Proteins / Q000502:physiology*; D004720:Endonucleases; D045585:Flap Endonucleases; D008938:Mitosis; D053484:RecQ Helicases; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology*; D015534:Trans-Activators / Q000502:physiology*
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; C061376:SRS2 protein, S cerevisiae; D004720:Endonucleases; D045585:Flap Endonucleases; C411624:MUS81 protein, S cerevisiae; C112337:MMS4 protein, S cerevisiae; C090472:SGS1 protein, S cerevisiae; D004265:DNA Helicases; D053484:RecQ Helicases; D004264:DNA Topoisomerases, Type I