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The yeast non-Mendelian factor [psi+] has been suggested to be a self-modified protein analogous to mammalian prions. Here it is reported that an intermediate amount of the chaperone protein Hsp104 was required for the propagation of the [psi+] factor. Over-production or inactivation of Hsp104 caused the loss of [psi+]. These results suggest that chaperone(More)
Prions are self-propagating protein conformations. Recent research brought insight into prion propagation, but how they first appear is unknown. We previously established that the yeast non-Mendelian trait [PIN(+)] is required for the de novo appearance of the [PSI(+)] prion. Here, we show that the presence of prions formed by Rnq1 or Ure2 is sufficient to(More)
Overproduced fusions of Sup35 or its prion domain with green fluorescent protein (GFP) have previously been shown to form frequent dots in [PSI(+)] cells. Rare foci seen in [psi(-)] cells were hypothesized to indicate the de novo induction of [PSI(+)] caused by the overproduced prion domain. Here, we describe novel ring-type aggregates that also appear in(More)
We have previously shown that multicopy plasmids containing the complete SUP35 gene are able to induce the appearance of the non-Mendelian factor [PSI]. This result was later interpreted by others as a crucial piece of evidence for a model postulating that [PSI] is a self-modified, prion-like conformational derivative of the Sup35 protein. Here we support(More)
The [PSI(+)] prion is the aggregated self-propagating form of the Sup35 protein from the yeast Saccharomyces cerevisiae. Aggregates of Sup35 in [PSI(+)] cells exist in different heritable conformations, called "variants," and they are composed of detergent-resistant Sup35 polymers, which may be closely associated with themselves, other proteins, or both.(More)
Although many proteins can misfold into a self-seeding amyloid-like conformation, only six are known to be infectious, that is prions. The prions [PSI(+)], [PIN(+)], [URE3], [SWI(+)] and [HET-s] cause distinct heritable physiological changes in fungi, whereas PrP(Sc) causes infectious encephalopathies in mammals. It is unknown whether 'protein-only'(More)
The concept of a prion as an infectious self-propagating protein isoform was initially proposed to explain certain mammalian diseases. It is now clear that yeast also has heritable elements transmitted via protein. Indeed, the "protein only" model of prion transmission was first proven using a yeast prion. Typically, known prions are ordered cross-β(More)
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(More)
It has previously been shown that yeast prion [PSI+] is cured by GuHCl, although reports on reversibility of curing were contradictory. Here we show that GuHCl treatment of both [PSI+] and [psi-] yeast strains results in two classes of [psi-] derivatives: Pin+, in which [PSI+] can be reinduced by Sup35p overproduction, and Pin-, in which overexpression of(More)
Prions are self-propagating, infectious protein conformations. The mammalian prion, PrP(Sc), responsible for neurodegenerative diseases like bovine spongiform encephalopathy (BSE; "mad cow" disease) and Creutzfeldt-Jakob's disease, appears to be a beta-sheet-rich amyloid conformation of PrP(c) that converts PrP(c) into PrP(Sc). However, an unequivocal(More)