The PNM2 mutation in the prion protein domain of SUP35 has distinct effects on different variants of the [PSI+] prion in yeast

Curr Genet. 1999 Mar;35(2):59-67. doi: 10.1007/s002940050433.


We have previously described different variants of the yeast prion [PSI+] that can be obtained and maintained in the same genetic background. These [PSI+] variants, which differ in the efficiency of nonsense suppression, mitotic stability and the efficiency of curing by GuHCl, may correspond to different [PSI+] prion conformations of Sup35p or to different types of prion aggregates. Here we investigate the effects of overexpressing a mutant allele of SUP35 and find different effects on weak and strong [PSI+] variants: the suppressor phenotype of weak [PSI+] factors is increased, whereas the suppressor effect of strong [PSI+] factors is reduced. The SUP35 mutation used was originally described as a "Psi no more" mutation (PNM2) because it caused loss of [PSI+]. However, none of the [PSI+] variants in the strains used in our study were cured by PNM2. Indeed, when overexpressed, PNM2 induced the de novo appearance of both weak and strong [PSI+] variants with approximately the same efficiency as the overexpressed wild-type SUP35 allele. Our data suggest that the change in the region of oligopeptide repeats in the Sup35p N-terminus due to the PNM2 mutation modifies, but does not impair, the function of the prion domain of Sup35p.

Publication types

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

MeSH terms

  • Alleles
  • Binding Sites
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics*
  • Fungal Proteins / metabolism
  • Gene Expression Regulation
  • Gene Expression Regulation, Fungal
  • Genetic Variation
  • Green Fluorescent Proteins
  • Luminescent Proteins / genetics
  • Mutation
  • Peptide Termination Factors
  • Prions / genetics*
  • Prions / metabolism
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins*


  • Fungal Proteins
  • Luminescent Proteins
  • Peptide Termination Factors
  • Prions
  • Recombinant Fusion Proteins
  • SUP35 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Green Fluorescent Proteins