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Published on: July 16, 2008
Yeast and Fungal Prions: Amyloid-Handling Systems, Amyloid Structure, and Prion Biology
R B Wickner1, H K Edskes1, A Gorkovskiy1
1National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, United States.
Abstract:
Yeast prions (infectious proteins) were discovered by their outré genetic properties and have become important models for an array of human prion and amyloid diseases. A single prion protein can become any of many distinct amyloid forms (called prion variants or strains), each of which is self-propagating, but with different biological properties (eg, lethal vs mild). The folded in-register parallel β sheet architecture of the yeast prion amyloids naturally suggests a mechanism by which prion variant information can be faithfully transmitted for many generations. The yeast prions rely on cellular chaperones for their propagation, but can be cured by various chaperone imbalances. The Btn2/Cur1 system normally cures most variants of the [URE3] prion that arise. Although most variants of the [PSI+] and [URE3] prions are toxic or lethal, some are mild in their effects. Even the most mild forms of these prions are rare in the wild, indicating that they too are detrimental to yeast. The beneficial [Het-s] prion of Podospora anserina poses an important contrast in its structure, biology, and evolution to the yeast prions characterized thus far.
Insights
Yeast prions, infectious proteins, can adopt diverse self-propagating forms with varying effects. While often detrimental, their propagation mechanisms and potential cures are key research areas.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Yeast prions are infectious proteins studied as models for human prion and amyloid diseases.
- A single prion protein can form multiple self-propagating variants (strains) with distinct biological properties.
- Yeast prions exhibit a folded in-register parallel β sheet architecture, suggesting a transmission mechanism.
Purpose of the Study:
- To investigate the mechanisms of yeast prion propagation and variant information transmission.
- To explore the role of cellular chaperones in prion propagation and curing.
- To understand the detrimental and beneficial aspects of different prion variants.
Main Methods:
- Analysis of yeast prion variants and their biological properties.
- Investigation of cellular chaperone systems, including the Btn2/Cur1 system.
- Comparative study of yeast prions with the beneficial [Het-s] prion.
Main Results:
- Yeast prions can exist as multiple variants, each with unique, self-propagating characteristics.
- Cellular chaperones are essential for prion propagation, and imbalances can lead to curing.
- Most yeast prion variants ([PSI+], [URE3]) are toxic or lethal, even mild forms are rare and detrimental.
Conclusions:
- The structure of yeast prions supports a mechanism for faithful transmission of variant information.
- The Btn2/Cur1 system plays a role in curing the [URE3] prion.
- The detrimental nature of most yeast prions contrasts with the beneficial [Het-s] prion, highlighting diverse prion roles.
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