Protein-based inheritance in Saccharomyces cerevisiae: [URE3] as a prion form of the nitrogen regulatory protein Ure2

How Big Is the Yeast Prion Universe?

The number of yeast prions and prion-like proteins described since 1994 has grown from two to nearly twenty. If in the early years most scientists working with the classic mammalian prion, PrP^Sc, were skeptical about the possibility of using the term prion to refer to yeast cytoplasmic elements with unusual properties, it is now clear that prion-like phenomena are widespread and that yeast can serve as a convenient model for studying them. Here we give a brief overview of the yeast prions discovered so far and focus our attention to the various approaches used to identify them. The prospects for the discovery of new yeast prions are also discussed.

Newly identified prions in budding yeast, and their possible functions

Yeast prions are atypical genetic elements that are transmitted as heritable protein conformations. [PSI+], [URE3], and [PIN+] are three well-studied prions in the budding yeast, Saccharomyces cerevisiae. In the last three years, several additional prions have been reported in yeast, including [SWI+], [OCT+], [MCA], [GAR+], [MOT3+], [ISP+], and [NSI+]. The growing number of yeast prions suggests that protein-based inheritance might be a widespread biological phenomenon. In this review, we summarize the characteristics of each prion element, and discuss their potential functional roles in yeast biology.

Development of a Novel Yeast Cell-Based System for Studying the Aggregation of Alzheimer’s Disease-Associated Aβ Peptides in vivo

Alzheimer's disease is the most common neurodegenerative disease, affecting approximately 50% of humans by age 85. The disease process is associated with aggregation of the Abeta peptides, short 39-43 residue peptides generated through endoproteolytic cleavage of the Alzheimer's precursor protein. While the process of aggregation of purified Abeta peptides in vitro is beginning to be well understood, little is known about this process in vivo. In the present study, we use the yeast Saccharomyces cerevisiae as a model system for studying Abeta-mediated aggregation in an organism in vivo. One of this yeast's endogenous prions, Sup35/[PSI+], loses the ability to aggregate when the prion-forming domain of this protein is deleted. We show that insertion of Abeta peptide sequences in place of the original prion domain of this protein restores its ability to aggregate. However, the aggregates are qualitatively different from [PSI+] prions in their sensitivity to detergents and in their requirements on trans-acting factors that are normally needed for [PSI+] propagation. We conclude that we have established a useful new tool for studying the aggregation of Abeta peptides in an organism in vivo.

Current awareness on yeast

In order to keep subscribers up-to-date with the latest developments in their field, this current awareness service is provided by John Wiley & Sons and contains newly-published material on yeasts. Each bibliography is divided into 10 sections. 1 Books, Reviews & Symposia; 2 General; 3 Biochemistry; 4 Biotechnology; 5 Cell Biology; 6 Gene Expression; 7 Genetics; 8 Physiology; 9 Medical Mycology; 10 Recombinant DNA Technology. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. (3 weeks journals - search completed 5th. Dec. 2001)