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.
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Molecular Cell Biology Laboratory, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi, Japan.
Satoh
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Onoda
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F
Miyajima
A
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Seki
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Enomoto
T
T
D000595:Amino Acid Sequence; D018906:Antineoplastic Agents, Alkylating / Q000494:pharmacology; D001816:Bloom Syndrome / Q000235:genetics; D004265:DNA Helicases / Q000235:genetics*; D004264:DNA Topoisomerases, Type I / Q000235:genetics*; D004351:Drug Resistance / Q000235:genetics; D006801:Humans; D008741:Methyl Methanesulfonate / Q000494:pharmacology; D008969:Molecular Sequence Data; D053484:RecQ Helicases; D011995:Recombination, Genetic; D011038:Rothmund-Thomson Syndrome / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014898:Werner Syndrome / Q000235:genetics
D018906:Antineoplastic Agents, Alkylating; D029701:Saccharomyces cerevisiae Proteins; D008741:Methyl Methanesulfonate; C090472:SGS1 protein, S cerevisiae; D004265:DNA Helicases; D053484:RecQ Helicases; D004264:DNA Topoisomerases, Type I