Yeast Prions Compared to Functional Prions and Amyloids

Saccharomyces cerevisiae is an occasional host to an array of prions, most based on self-propagating, self-templating amyloid filaments of a normally soluble protein. URE3] is a prion of Ure2p, a regulator of nitrogen catabolism, while PSI +] is a prion of Sup35p, a subunit of the translation termination factor Sup35p. In contrast to the functional prions, Het-s] of Podospora anserina and BETA] of yeast, the amyloid-based yeast prions are rare in wild strains, arise sporadically, have an array of prion variants for a single prion protein sequence, have a folded in-register parallel β-sheet amyloid architecture, are detrimental to their hosts, arouse a stress response in the host, and are subject to curing by various host anti-prion systems. These characteristics allow a logical basis for distinction between functional amyloids/prions and prion diseases. These infectious yeast amyloidoses are outstanding models for the many common human amyloid-based diseases that are increasingly found to have some infectious characteristics.