Meiotic chromosome synapsis-promoting proteins antagonize the anti-crossover activity of sgs1

PLoS Genet. 2006 Sep 22;2(9):e155. doi: 10.1371/journal.pgen.0020155. Epub 2006 Aug 2.


Sgs1, the budding yeast homolog of the mammalian BLM helicase, has been implicated in preventing excess recombination during both vegetative growth and meiosis. Most meiotic crossover (CO) recombination requires full function of a set of yeast proteins (Zip1, Zip2, Zip3, Zip4/Spo22, Mer3, Msh4, and Msh5, termed the SIC or ZMM proteins) that are also required for homologous chromosome synapsis. We report here genetic and molecular assays showing that sgs1 single mutants display relatively modest increases in CO recombination (less than 1.6-fold relative to wild-type). In contrast, a much greater CO increase is seen when an sgs1 mutation is introduced into the CO- and synapsis-deficient zip1, zip2, zip3, mer3, or msh4 mutants (2- to 8-fold increase). Furthermore, close juxtaposition of the axes of homologous chromosomes is restored. CO restoration in the mutants is not accompanied by significant changes in noncrossover (NCO) recombinant frequencies. These findings show that Sgs1 has potent meiotic anti-CO activity, which is normally antagonized by SIC/ZMM proteins. Our data reinforce previous proposals for an early separation of meiotic processes that form CO and NCO recombinants.

Publication types

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

MeSH terms

  • Chromosome Pairing / physiology*
  • Chromosomes, Fungal / genetics
  • Chromosomes, Fungal / metabolism*
  • Crossing Over, Genetic*
  • DNA Helicases / deficiency
  • DNA Helicases / metabolism*
  • Molecular Sequence Data
  • Mutation / genetics
  • RecQ Helicases
  • Saccharomyces cerevisiae / cytology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Spores, Fungal / metabolism


  • Saccharomyces cerevisiae Proteins
  • SGS1 protein, S cerevisiae
  • DNA Helicases
  • RecQ Helicases

Associated data

  • SWISSPROT/P02557
  • SWISSPROT/P14291
  • SWISSPROT/P23179
  • SWISSPROT/P31111
  • SWISSPROT/P32562
  • SWISSPROT/P35187
  • SWISSPROT/P38830
  • SWISSPROT/P40511
  • SWISSPROT/P40965
  • SWISSPROT/P51979
  • SWISSPROT/P53061
  • SWISSPROT/P54132
  • SWISSPROT/Q06032
  • SWISSPROT/Q12175
  • SWISSPROT/Q13472