Molecular and General Genetics MGG

, Volume 264, Issue 1, pp 89–97

Genetic analysis of the Saccharomyces cerevisiae Sgs1 helicase defines an essential function for the Sgs1-Top3 complex in the absence of SRS2 or TOP1

Authors

  • M. Dunø
    • Section for Molecular Genetics, Danish Institute of Agricultural Sciences, P.O. Box 50, DK-8830 Tjele
  • B. Thomsen
    • Section for Molecular Genetics, Danish Institute of Agricultural Sciences, P.O. Box 50, DK-8830 Tjele
  • O. Westergaard
    • Department of Molecular and Structural Biology, University of Aarhus, C. F. Møllers Allé, Bldg. 130, DK-8000 Aarhus C
  • L. Krejci
    • Section for Molecular Genetics, Danish Institute of Agricultural Sciences, P.O. Box 50, DK-8830 Tjele
  • C. Bendixen
    • Section for Molecular Genetics, Danish Institute of Agricultural Sciences, P.O. Box 50, DK-8830 Tjele
Original Paper

DOI: 10.1007/s004380000286

Cite this article as:
Dunø, M., Thomsen, B., Westergaard, O. et al. Mol Gen Genet (2000) 264: 89. doi:10.1007/s004380000286

Abstract

The Saccharomyces cerevisiae gene SGS1 encodes a DNA helicase that shows homology to the Escherichia coli protein RecQ and the products of the BLM and WRN genes in humans, which are defective in Bloom’s and Werner’s syndrome, respectively. Recently, it has been proposed that this helicase is involved in maintaining the integrity of the rDNA and that loss of Sgs1 function leads to accelerated aging. Sgs1 has been isolated on the basis of its genetic interaction with both topoisomerase I and topoisomerase III, as well as in a two-hybrid screen for proteins that interact with the C-terminal portion of topoisomerase II. We have defined the minimal structural elements of Sgs1 required for its interactions with the three topoisomerases, and demonstrate that the complex phenotypes associated with sgs1 mutants are a consequence of a dysfunctional Sgs1-Top3 complex. We also report that the synthetic relationship between mutations in SGS1 and SRS2, which encodes another helicase implicated in recombinational repair, likewise result from a dysfunctional Sgs1-Top3 interaction. Our findings indicate that Sgs1 may act on different DNA structures depending on the activity of topoisomerase I, Srs2 and topoisomerase III.

Helicase Two-hybrid system SGS1 Topoisomerase.
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© Springer-Verlag 2000