title: Saccharomyces cerevisiae: a sexy yeast with a prion problem.
abstract: Yeast prions are infectious proteins that spread exclusively by mating. The frequency of prions in the wild therefore largely reflects the rate of spread by mating counterbalanced by prion growth slowing effects in the host. We recently showed that the frequency of outcross mating is about 1% of mitotic doublings with 23-46% of total matings being outcrosses. These findings imply that even the mildest forms of the [PSI+], [URE3] and [PIN+] prions impart > 1% growth/survival detriment on their hosts. Our estimate of outcrossing suggests that Saccharomyces cerevisiae is far more sexual than previously thought and would therefore be more responsive to the adaptive effects of natural selection compared with a strictly asexual yeast. Further, given its large effective population size, a growth/survival detriment of > 1% for yeast prions should strongly select against prion-infected strains in wild populations of Saccharomyces cerevisiae.
authors.affiliation: Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Kelly
authors.forename: Reed B
authors.initials: RB
authors.lastname: Wickner
mesh_terms: D000818:Animals; D006801:Humans; D011328:Prions / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000166:cytology* / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*; D012641:Selection, Genetic
chemical_list: D011328:Prions; D029701:Saccharomyces cerevisiae Proteins
keywords: effective population size; evolutionary constraint; fitness; outcross