The utility of prions.

Infectious, self-propagating protein aggregates (prions) as well as structurally related amyloid fibrils have traditionally been associated with neurodegenerative diseases in mammals. However, recent work in fungi indicates that prions are not simply aberrations of protein folding, but are in fact widespread, conserved, and in certain cases, apparently beneficial. Analysis of prion behavior in yeast has led to insights into the mechanisms of prion appearance and propagation as well as the effect of prions on cellular physiology and perhaps evolution. The prion-forming proteins of Saccharomyces cerevisiae are members of a larger class of Gln/Asn-rich proteins that is abundantly represented in the genomes of higher eukaryotes, raising the prospect of genetically programmed prion-like behavior in other organisms.