A yeast prion provides a mechanism for genetic variation and phenotypic diversity

Nature. 2000 Sep 28;407(6803):477-83. doi: 10.1038/35035005.


A major enigma in evolutionary biology is that new forms or functions often require the concerted effects of several independent genetic changes. It is unclear how such changes might accumulate when they are likely to be deleterious individually and be lost by selective pressure. The Saccharomyces cerevisiae prion [PSI+] is an epigenetic modifier of the fidelity of translation termination, but its impact on yeast biology has been unclear. Here we show that [PSI+] provides the means to uncover hidden genetic variation and produce new heritable phenotypes. Moreover, in each of the seven genetic backgrounds tested, the constellation of phenotypes produced was unique. We propose that the epigenetic and metastable nature of [PSI+] inheritance allows yeast cells to exploit pre-existing genetic variation to thrive in fluctuating environments. Further, the capacity of [PSI+] to convert previously neutral genetic variation to a non-neutral state may facilitate the evolution of new traits.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Binding Sites
  • Ethanol / pharmacology
  • Fungal Proteins / genetics*
  • Fungal Proteins / physiology
  • Genetic Variation*
  • Peptide Termination Factors
  • Phenotype
  • Prions / genetics*
  • Prions / physiology
  • Protein Biosynthesis / drug effects
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae Proteins*


  • Anti-Bacterial Agents
  • Fungal Proteins
  • Peptide Termination Factors
  • Prions
  • SUP35 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Ethanol