Prions: infectious proteins with genetic properties.

The data on prions--proteinaceous infectious agents--are briefly summarized. Prions cause several incurable neurodegenerative diseases in mammals, while in lower eukaryotes the prion properties of proteins may be responsible for the inheritance of some phenotypic traits. The novel experimental models for finding and studying proteins with prion properties based on the yeast Saccharomyces cerevisiae and the fungus Podospora anserina are described. The significance of the prion phenomenon for biology and medicine is discussed.