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Novel yeast killer toxins provoke S-phase arrest and DNA damage checkpoint activation

Roland Klassen1, Sabine Teichert, Friedhelm Meinhardt

  • 1Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Corrensstr. 3, D-48149 Münster, Germany.

Molecular Microbiology
|July 1, 2004
PubMed

Insights

Novel killer toxins from Pichia acaciae and Wingea robertsiae, distinct from Kluyveromyces lactis zymocin, arrest the cell cycle in S phase. DNA damage checkpoint activation aids in coping with these yeast toxins.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Yeast Genetics

Background:

  • Extranuclear genetic elements in Pichia acaciae and Wingea robertsiae confer a killer phenotype.
  • Killer plasmids (pPac1-2 and pWR1A) are related to each other but only partly similar to the zymocin plasmid (pGKL1) of Kluyveromyces lactis.
  • Yeast killer toxins target chitin synthase (Chs3) and possess functions for toxin binding and uptake.

Purpose of the Study:

  • To sequence and compare killer plasmids from P. acaciae and W. robertsiae with K. lactis pGKL1.
  • To characterize the mode of action and cell cycle effects of P. acaciae and W. robertsiae toxins.
  • To investigate the role of the DNA damage checkpoint in response to these novel yeast toxins.

Main Methods:

  • Plasmid sequencing and comparative analysis.
  • Heterologous expression of toxin genes and functional analysis.
  • Fluorescence-activated cell sorting (FACS) and budding index determination.
  • Analysis of DNA damage checkpoint activation (Rad53 phosphorylation) and mutant phenotypes.

Main Results:

  • P. acaciae and W. robertsiae killer plasmids encode toxins structurally different from K. lactis zymocin.
  • These novel toxins induce cell cycle arrest post-G1, specifically during the S phase, independent of RNA polymerase II Elongator.
  • Toxin action triggers Rad53 phosphorylation, indicating DNA damage checkpoint activation, which contributes to stress response rather than direct toxicity.

Conclusions:

  • Pichia acaciae and Wingea robertsiae toxins exhibit a distinct mode of action compared to Kluyveromyces lactis zymocin.
  • The identified toxins mediate S-phase cell cycle arrest, highlighting a novel mechanism of yeast toxicity.
  • DNA damage checkpoint activation plays a role in the cellular response to these specific yeast toxins.

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