Propagation of the yeast prion-like [psi+] determinant is mediated by oligomerization of the SUP35-encoded polypeptide chain release factor.
The Sup35p protein of yeast Saccharomyces cerevisiae is a homologue of the polypeptide chain release factor 3 (eRF3) of higher eukaryotes. It has been suggested that this protein may adopt a specific self-propagating conformation, similar to mammalian prions, giving rise to the [psi+] nonsense suppressor determinant, inherited in a non-Mendelian fashion. Here we present data confirming the prion-like nature of [psi+]. We show that Sup35p molecules interact with each other through their N-terminal domains in [psi+], but not [psi-] cells. This interaction is critical for [psi+] propagation, since its disruption leads to a loss of [psi+]. Similarly to mammalian prions, in [psi+] cells Sup35p forms high molecular weight aggregates, accumulating most of this protein. The aggregation inhibits Sup35p activity leading to a [psi+] nonsense-suppressor phenotype. N-terminally altered Sup35p molecules are unable to interact with the [psi+] Sup35p isoform, remain soluble and improve the translation termination in [psi+] strains, thus causing an antisuppressor phenotype. The overexpression of Hsp104p chaperone protein partially solubilizes Sup35P aggregates in the [psi+] strain, also causing an antisuppressor phenotype. We propose that Hsp104p plays a role in establishing stable [psi+] inheritance by splitting up Sup35p aggregates and thus ensuring equidistribution of the prion-like Sup35p isoform to daughter cells at cell divisions.
Paushkin
S V
SV
Institute of Experimental Cardiology, Cardiology Research Center, Moscow, Russia.
Kushnirov
V V
VV
Smirnov
V N
VN
Ter-Avanesyan
M D
MD
D000483:Alleles; D001483:Base Sequence; D001704:Biopolymers; D010450:Endopeptidases / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides; D010454:Peptide Termination Factors; D011328:Prions / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins
D001704:Biopolymers; D005656:Fungal Proteins; D009838:Oligodeoxyribonucleotides; D010454:Peptide Termination Factors; D011328:Prions; C068068:SUP35 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D010450:Endopeptidases