Self-seeded fibers formed by Sup35, the protein determinant of [PSI+], a heritable prion-like factor of S. cerevisiae

Cell. 1997 May 30;89(5):811-9. doi: 10.1016/s0092-8674(00)80264-0.


The [PSI+] factor of S. cerevisiae represents a new form of inheritance: cytosolic transmission of an altered phenotype is apparently based upon inheritance of an altered protein structure rather than an altered nucleic acid. The molecular basis of its propagation is unknown. We report that purified Sup35 and subdomains that induce [PSI+] elements in vivo form highly ordered fibers in vitro. Fibers bind Congo red and are rich in beta sheet, characteristics of amyloids found in certain human diseases, including the prion diseases. Some fibers have distinct structures and these, once initiated, are self-perpetuating. Preformed fibers greatly accelerate fiber formation by unpolymerized protein. These data support a "protein-only" seeded polymerization model for the inheritance of [PSI+].

Publication types

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

MeSH terms

  • Fungal Proteins / chemistry*
  • Fungal Proteins / ultrastructure
  • Humans
  • Microscopy, Electron
  • Peptide Termination Factors
  • Prions / chemistry*
  • Prions / ultrastructure
  • Protein Conformation
  • Saccharomyces cerevisiae Proteins*
  • Saccharomyces cerevisiae*


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