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Sequestration of essential proteins causes prion associated toxicity in yeast

Namitha Vishveshwara1, Michael E Bradley, Susan W Liebman

  • 1Department of Biological Sciences, Laboratory for Molecular Biology, University of Illinois at Chicago, Chicago, IL 60607, USA.

Molecular Microbiology
|August 18, 2009
PubMed

Insights

Yeast prion toxicity from excess Sup35p protein is rescued by Sup35Cp, with rescue levels proportional to Sup35p overexpression. Sup45p binding partners also play a role in mitigating this prion toxicity.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Prion Biology

Background:

  • Prions are infectious protein aggregates causing mammalian diseases.
  • In yeast, the Sup35p protein can form the [PSI(+)] prion, which can inhibit cell growth.
  • The Sup35Cp domain of Sup35p can rescue this toxicity without affecting prion propagation.

Purpose of the Study:

  • Investigate the mechanism of Sup35p prion toxicity rescue in yeast.
  • Determine the role of Sup35Cp levels and Sup45p binding partners in mitigating toxicity.
  • Differentiate the toxicity mechanisms of excess Sup35p versus its prion domain (Sup35NMp).

Main Methods:

  • Yeast genetics and protein overexpression techniques.
  • Fluorescence microscopy to observe protein aggregate formation and colocalization (Sup35-RFPp and Sup45-GFPp).
  • Assessing cell growth inhibition and rescue phenotypes.

Main Results:

  • Toxicity rescue by Sup35Cp requires levels proportional to Sup35p overexpression.
  • Overexpression of Sup45p, a Sup35p binding partner, also rescues Sup35p toxicity.
  • Sup45p colocalizes with Sup35p aggregates during toxicity, suggesting sequestration.
  • Toxicity from excess Sup35NMp is rescued differently, not involving Sup45p.

Conclusions:

  • Yeast prion toxicity from excess Sup35p involves Sup45p sequestration.
  • Toxicity from excess Sup35NMp appears to directly involve Sup35p.
  • Differential mechanisms explain toxicity from full-length Sup35p versus its prion domain.

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