Dependence and independence of [PSI(+)] and [PIN(+)]: a two-prion system in yeast?
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.
Derkatch
I L
IL
Laboratory for Molecular Biology, Department of Biological Sciences, University of Illinois at Chicago, 900 South Ashland Avenue, Chicago, IL 60607, USA.
Bradley
M E
ME
Masse
S V
SV
Zadorsky
S P
SP
Polozkov
G V
GV
Inge-Vechtomov
S G
SG
Liebman
S W
SW
D000595:Amino Acid Sequence; D001685:Biological Factors / Q000235:genetics / Q000502:physiology*; D003080:Cold Temperature; D003433:Crosses, Genetic; D005656:Fungal Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D019791:Guanidine / Q000494:pharmacology; D008938:Mitosis; D008954:Models, Biological; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010454:Peptide Termination Factors; D010641:Phenotype; D010957:Plasmids / Q000235:genetics; D011328:Prions / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary / Q000187:drug effects; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins; D017384:Sequence Deletion / Q000235:genetics; D013997:Time Factors
D001685:Biological Factors; D005656:Fungal Proteins; D010446:Peptide Fragments; D010454:Peptide Termination Factors; D011328:Prions; C068068:SUP35 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D019791:Guanidine