Introduction to yeast and fungal prions

Abstract

Prions are infectious proteins, not requiring an accompanying nucleic acid for the transmission to a new individual. In 1994, we found that the long-known cytoplasmic genes [URE3] and [PSI+] were actually prions of Ure2p and Sup35p, respectively. These, and a variety of yeast and fungal prions found since then are based on self-propagating amyloids, but one prion based on a protease that self-activates shows that not all infectious proteins need be amyloids. The importance of chaperones in prion propagation, the involvement of many other cellular systems, and development of anti-prion measures-some potentially active against mammalian prions, have enriched the prion field. The in-register parallel architecture of yeast prion amyloids can explain how a single protein can faithfully propagate any of several structurally different prion variants/strains. Discovery of an array of new prions, and interesting new variants of old prions continues to expand our understanding of this phenomenon.