Sgs1 function in the repair of DNA replication intermediates is separable from its role in homologous recombinational repair

EMBO J. 2009 Apr 8;28(7):915-25. doi: 10.1038/emboj.2009.28. Epub 2009 Feb 12.


Mutations in human homologues of the bacterial RecQ helicase cause diseases leading to cancer predisposition and/or shortened lifespan (Werner, Bloom, and Rothmund-Thomson syndromes). The budding yeast Saccharomyces cerevisiae has one RecQ helicase, Sgs1, which functions with Top3 and Rmi1 in DNA repair. Here, we report separation-of-function alleles of SGS1 that suppress the slow growth of top3Delta and rmi1Delta cells similar to an SGS1 deletion, but are resistant to DNA damage similar to wild-type SGS1. In one allele, the second acidic region is deleted, and in the other, only a single aspartic acid residue 664 is deleted. sgs1-D664Delta, unlike sgs1Delta, neither disrupts DNA recombination nor has synthetic growth defects when combined with DNA repair mutants. However, during S phase, it accumulates replication-associated X-shaped structures at damaged replication forks. Furthermore, fluorescent microscopy reveals that the sgs1-D664Delta allele exhibits increased spontaneous RPA foci, suggesting that the persistent X-structures may contain single-stranded DNA. Taken together, these results suggest that the Sgs1 function in repair of DNA replication intermediates can be uncoupled from its role in homologous recombinational repair.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • DNA Repair / physiology*
  • DNA Replication / physiology*
  • DNA, Fungal / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • Microscopy, Fluorescence
  • Mutation
  • Phenotype
  • RecQ Helicases / genetics
  • RecQ Helicases / physiology*
  • Recombination, Genetic*
  • Replication Protein A
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism
  • Saccharomyces cerevisiae Proteins / physiology*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism


  • DNA, Fungal
  • DNA-Binding Proteins
  • RFA1 protein, S cerevisiae
  • Replication Protein A
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • SGS1 protein, S cerevisiae
  • RecQ Helicases