Extrachromosomal elements in a super-suppression system of yeast II. Relations with other extrachromosomal elements

Young, C. S. H.; Cox, Brian S.

doi:10.1038/hdy.1972.24

Cited by 32 publications

(12 citation statements)

References 17 publications

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“…GuHCl might plausibly elicit curing if it blocked the self-replication of a [PSI ϩ ]-encoding nucleic acid species. However, unlike curing of [PSI ϩ ], growth is not a prerequisite for petite induction in yeast (32) and despite the identification of many plasmids and viruses of yeast (33), no extrachromosomal nucleic acid has ever been linked to [PSI ϩ ] (34,35).…”

Section: Discussionmentioning

confidence: 99%

Guanidine hydrochloride blocks a critical step in the propagation of the prion-like determinant [ PSI ⁺ ] of Saccharomyces cerevisiae

Eaglestone

Ruddock

Cox

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

175

210

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The cytoplasmic heritable determinant [PSI ؉ ] of the yeast Saccharomyces cerevisiae reflects the prion-like properties of the chromosome-encoded protein Sup35p. This protein is known to be an essential eukaryote polypeptide release factor, namely eRF3. In a [PSI ؉ ] background, the prion conformer of Sup35p forms large oligomers, which results in the intracellular depletion of functional release factor and hence inefficient translation termination. We have investigated the process by which the [ curing ͉ Sup35p ͉ cytoplasmic determinant R ecent biochemical evidence (1-5) has supported the hypothesis that the [PSI ϩ ] phenotype of Saccharomyces cerevisiae reflects the prion-like properties of the SUP35 gene product (6, 7). The essential chromosome-encoded protein Sup35p is known to be one of two eukaryote polypeptide release factors, namely eRF3 (8, 9). Sup35p associates with Sup45p (eRF1) in vivo to mediate translation termination (8). In vitro, Sup35p forms highly ordered fibers, whose appearance resembles that of fibrils formed by other amyloidogenic polypeptides (3,4 , a second prion determinant of S. cerevisiae (7). Other reagents including methanol, ethylene glycol, and hypertonic conditions, have been reported to exhibit curing properties; however, none of these cure with the neartotal efficiency of GuHCl (13,14).Two hypotheses have been proposed to account for the curing properties of GuHCl. First, the elimination of the prion might arise directly from the ability of GuHCl to denature proteins. However, the concentrations of GuHCl effective in curing [PSI ϩ ] are in the millimolar range, rather than the molar range typically required for the denaturation of proteins in vitro (13). Alternatively, GuHCl may actually promote the expression of an ancillary factor, namely the stress protein Hsp104p, which indirectly results in the reactivation of Sup35p and consequently the loss of the prion (15). Unlike other heat shock proteins, Hsp104p does not act to protect proteins against stress (i.e., heat denaturation), rather Hsp104p actively promotes the recovery of stress-denatured aggregated proteins by facilitating their refolding back into functional, native conformations (16,17). Overexpression of Hsp104p might lead to the total refolding of Sup35p from the aberrant prion conformation to its native structure, thereby mediating prion loss. To test both hypotheses, we have examined the kinetics of prion elimination upon growth in the presence of GuHCl and assessed the influence of stress on the curing process. Materials and MethodsStrain. The genotype of the strain used in this study was BSC783͞4a: , MATa. Growth Media. BSC783͞4a was grown at 30°C on 1 ⁄4YEPD solid medium [4% (wt͞vol) glucose, 1% (wt͞vol) Bacto-peptone, 0.25% (wt͞vol) yeast extract, 2% (wt͞vol) agar]. Most liquid cultures also were grown at 30°C in YEPD complete medium [2% (wt͞vol) glucose, 1% (wt͞vol) Bacto-peptone, 1% (wt͞vol) yeast extract], with or without 3 mM GuHCl. For studies using ethanol-supplemented media, strains were grown in f...

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Section: Discussionmentioning

confidence: 99%

Guanidine hydrochloride blocks a critical step in the propagation of the prion-like determinant [ PSI ⁺ ] of Saccharomyces cerevisiae

Eaglestone

Ruddock

Cox

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

175

210

View full text Add to dashboard Cite

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“…Consistent with this non-Mendelian segregation, the [PSI ϩ ] factor appeared to be located in the cytoplasm because it was transmitted by cytoduction when the cytoplasm of a [PSI ϩ ] donor haploid was transferred to a [psi Ϫ ] recipient haploid without altering the recipient's nucleus (2). Thus it was possible that a cytoplasmic nucleic acid encoded [PSI ϩ ], although it was shown not to depend upon mitochondrial DNA, 2 DNA, killer viruses, or 20 S RNA (2,12,13).…”

Section: Discovery Of [Psi ؉ ]mentioning

confidence: 99%

The Yeast [PSI+] Prion: Making Sense of Nonsense

Liebman

Derkatch

1999

Journal of Biological Chemistry

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] was shown to be an "omnipotent" suppressor because it could cause readthrough of certain UAA, UAG, and UGA codons in the absence of other suppressors or drugs (11). Similar allosuppressor and omnipotent suppressor phenotypes were also associated with different sup35 and sup45 mutant alleles. However, whereas the sup35 and sup45 mutations were recessive and showed the 2:2 segregation pattern expected of Mendelian genes, the [PSI

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“…Tetrad and heterokaryon analyses have demonstrated that the t+ determinant resides outside the nucleus (1,7). Genetic analysis with other types of cytoplasmic mutants indicated that the 4 determinant is not associated with mitochondrial DNA (8) or with the double-stranded RNA that controls the "killer" phenotype (9). Although the molecular identity of 4 is unknown, it is believed to be a self-replicating cytoplasmic factor that either directly or indirectly affects the translational process.…”

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confidence: 99%

Mutation of the non-Mendelian suppressor, Ψ ⁺ , in yeast by hypertonic media

Singh

Helms

Sherman

1979

Proc. Natl. Acad. Sci. U.S.A.

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The 4+ extrachromosomal determinant in the yeast Saccharomyces cerevisiae suppresses certain UAA markers and increases the efficiency of suppression of UAA suppressors and certain frameshift suppressors. Although the exact nature of 4+ determinant is unknown, it is believed to be a self-replicating cytoplasmic factor affecting some component of the translational machinery. In this report we describe growth conditions for efficient mutation or elimination of the 4+ determinant. Incubation of 4+ cultures in hypertonic nutrient medium resulted in rapid conversion to a culture containing predominantly 4-cells during the growth cycle. The kinetics of + to 4-conversion established that the occurrence of 4-cells was due to induction and not to selection of pre-existing 4-cells. The results suggest that the replication of the A+ determinant is sensitive to hypertonic conditions. Media. The routine nutrient medium contained 1% Bactoyeast extract, 2% Bacto-peptone, and 2% dextrose. The hypertonic media were prepared by supplementing the nutrient medium with potassium chloride or ethylene glycol. Glycerol medium consisted of 1% Bacto-yeast extract, 2% Bacto-peptone, and 3% (vol/vol) glycerol. Either 1% or 2% Noble agar was added if solidification was desired.Population Analysis. Freshly grown cells were inoculated into hypertonic media to an initial titer of approximately 106 cells/ml. The cultures were incubated at 300C with vigorous shaking. At various times samples were withdrawn, sonicated to disperse the cell clusters, and plated on nutrient medium after appropriate dilutions. In some experiments the cells were also plated on a nutrient medium containing 10% dextrose, a medium that intensifies the red coloration conferred by the ade2-1 marker (11). The nutrient plates were incubated at 30'C and the number and types of the resulting colonies were scored after 3-5 days. At least 5000-8000 colonies were scored when the 41 cells were relatively rare at early incubation times. Cell densities allowing approximately 200 colonies per plate were used for most experiments, whereas higher densities, allowing colonies per plate, were used for examining the cell types during the first 4 hr of incubation of the cultures in ethylene glycol. The numbers of 0-red colonies could be accurately counted over the high background of white colonies.In some experiments the growth in liquid hypertonic media was monitored by measuring the turbidity with a Klett-Summerson photoelectric colorimeter equipped with a no. 62 light filter.Phenotypes. The degree of suppression in strains carrying various UAA markers can be conveniently estimated from the growth on omission media and from the degree of coloration conferred by the ade2-1 marker. Although these properties can vary with different strains, the patterns usually observed are presented in Table 2

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Extrachromosomal elements in a super-suppression system of yeast II. Relations with other extrachromosomal elements

Cited by 32 publications

References 17 publications

Guanidine hydrochloride blocks a critical step in the propagation of the prion-like determinant [ PSI ⁺ ] of Saccharomyces cerevisiae

Guanidine hydrochloride blocks a critical step in the propagation of the prion-like determinant [ PSI ⁺ ] of Saccharomyces cerevisiae

The Yeast [PSI+] Prion: Making Sense of Nonsense

Mutation of the non-Mendelian suppressor, Ψ ⁺ , in yeast by hypertonic media

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Extrachromosomal elements in a super-suppression system of yeast II. Relations with other extrachromosomal elements

Cited by 32 publications

References 17 publications

Guanidine hydrochloride blocks a critical step in the propagation of the prion-like determinant [ PSI + ] of Saccharomyces cerevisiae

Guanidine hydrochloride blocks a critical step in the propagation of the prion-like determinant [ PSI + ] of Saccharomyces cerevisiae

The Yeast [PSI+] Prion: Making Sense of Nonsense

Mutation of the non-Mendelian suppressor, Ψ + , in yeast by hypertonic media

Contact Info

Product

Resources

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Guanidine hydrochloride blocks a critical step in the propagation of the prion-like determinant [ PSI ⁺ ] of Saccharomyces cerevisiae

Guanidine hydrochloride blocks a critical step in the propagation of the prion-like determinant [ PSI ⁺ ] of Saccharomyces cerevisiae

Mutation of the non-Mendelian suppressor, Ψ ⁺ , in yeast by hypertonic media