neurodegenerative disease, yeast protein
Prions, responsible for such neurodegenerative diseases as mad-cow disease and scrapie, are proteins that transmit a trait without the use of conventional genetic material (DNA or RNA). Prions’ infectivity arises from their tendency to adopt an altered conformation that induces the normally folded prion protein to change its shape as well. My lab started out studying yeast protein chaperones, which help proteins fold properly or, in the event of environmental stress, refold properly. One chaperone, Hsp104, has the unique role of breaking up protein aggregates. The discovery that Hsp104 mediates a yeast phenotype, called [PSI+], that shows a prion-like pattern of inheritance altered the course of my work dramatically. My lab has since found that [PSI+] arises from the altered conformation of a translation termination factor, Sup35, resulting in insoluble aggregates. Paradoxically, either deletion or overexpression of Hsp104 abolishes [PSI+]. One of our more astounding findings was that whereas mammalian prions are harmful, yeast prions can be beneficial. In one fungus, prions are even essential for survival during part of its life cycle. Thus, in addition to providing a simple system in which to study prion genetics, yeast has broadened our view of prion function overall.
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