Dependence and independence of [PSI(+)] and [PIN(+)]: a two-prion system in yeast?

EMBO J. 2000 May 2;19(9):1942-52. doi: 10.1093/emboj/19.9.1942.


The [PSI(+)] prion can be induced by overproduction of the complete Sup35 protein, but only in strains carrying the non-Mendelian [PIN(+)] determinant. Here we demonstrate that just as [psi (-)] strains can exist as [PIN(+)] and [pin(-)] variants, [PSI(+)] can also exist in the presence or absence of [PIN(+)]. [PSI(+)] and [PIN(+)] tend to be cured together, but can be lost separately. [PSI(+)]-related phenotypes are not affected by [PIN(+)]. Thus, [PIN(+)] is required for the de novo formation of [PSI(+)], not for [PSI(+)] propagation. Although [PSI(+)] induction is shown to require [PIN(+)] even when the only overexpressed region of Sup35p is the prion domain, two altered prion domain fragments circumventing the [PIN(+)] requirement are characterized. Finally, in strains cured of [PIN(+)], prolonged incubation facilitates the reappearance of [PIN(+)]. Newly appearing [PIN(+)] elements are often unstable but become stable in some mitotic progeny. Such reversibility of curing, together with our previous demonstration that the inheritance of [PIN(+)] is non-Mendelian, supports the hypothesis that [PIN(+)] is a prion. Models for [PIN(+)] action, which explain these findings, are discussed.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Biological Factors / genetics
  • Biological Factors / physiology*
  • Cold Temperature
  • Crosses, Genetic
  • Fungal Proteins / chemistry*
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Expression
  • Guanidine / pharmacology
  • Mitosis
  • Models, Biological
  • Molecular Sequence Data
  • Peptide Fragments / chemistry
  • Peptide Fragments / genetics
  • Peptide Fragments / metabolism
  • Peptide Termination Factors
  • Phenotype
  • Plasmids / genetics
  • Prions / chemistry*
  • Prions / genetics
  • Prions / metabolism*
  • Protein Structure, Tertiary / drug effects
  • Saccharomyces cerevisiae Proteins*
  • Saccharomyces cerevisiae* / chemistry
  • Saccharomyces cerevisiae* / drug effects
  • Saccharomyces cerevisiae* / genetics
  • Saccharomyces cerevisiae* / growth & development
  • Sequence Deletion / genetics
  • Time Factors


  • Biological Factors
  • Fungal Proteins
  • Peptide Fragments
  • Peptide Termination Factors
  • Prions
  • SUP35 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Guanidine