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The N-terminal region of Sgs1, which interacts with Top3, is required for complementation of MMS sensitivity and suppression of hyper-recombination in sgs1 disruptants.

The SGS1 gene of Saccharomyces (cerevisiae is a homologue of the genes affected in Bloom's syndrome, Werner's syndrome, and Rothmund-Thomson's syndrome. Disruption of the SGS1 gene is associated with high sensitivity to methyl methanesulfonate (MMS) and hydroxyurea (HU), and with hyper-recombination phenotypes, including interchromosomal recombination between heteroalleles. SGS1 encodes a protein which has a helicase domain similar to that of Escherichia coli RecQ. A comparison of amino acid sequences among helicases of the RecQ family reveals that Sgs1,WRN, and BLM share a conserved region adjacent to the C-terminal part of the helicase domain (C-terminal conserved region). In addition, Sgs1 contains two highly charged acidic regions in its N-terminal region and the HRDC (helicase and RNaseD C-terminal) domain at its C-terminal end. These regions were also found in BLM and WRN, and in Rqh1 from Schizosaccharomyces pombe. In this study, we demonstrate that the C-terminal conserved region, as well as the helicase motifs, of Sgs1 are essential for complementation of MMS sensitivity and suppression of hyper-recombination in sgs1 mutants. In contrast, the highly charged acidic regions, the HRDC domain, and the C-terminal 252 amino acids were dispensable for the complementation of these phenotypes. Surprisingly, the N-terminal 45 amino acids of Sgs1 were absolutely required for the suppression of the above phenotypes. Introduction of missense mutations into the region encoding amino acids 4-13 abolished the ability of Sgsl to complement MMS sensitivity and suppress hyper-recombination in sgs1 mutants, and also prevented its interaction with Top3, indicating that interaction with Top3 via the N-terminal region of Sgs1 is involved in the complementation of MMS sensitivity and the suppression of hyper-recombination.

Pubmed ID: 11523801


  • Ui A
  • Satoh Y
  • Onoda F
  • Miyajima A
  • Seki M
  • Enomoto T


Molecular genetics and genomics : MGG

Publication Data

July 28, 2001

Associated Grants


Mesh Terms

  • Amino Acid Sequence
  • Antineoplastic Agents, Alkylating
  • Bloom Syndrome
  • DNA Helicases
  • DNA Topoisomerases, Type I
  • Drug Resistance
  • Humans
  • Methyl Methanesulfonate
  • Molecular Sequence Data
  • RecQ Helicases
  • Recombination, Genetic
  • Rothmund-Thomson Syndrome
  • Saccharomyces cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Sequence Alignment
  • Sequence Homology, Nucleic Acid
  • Werner Syndrome