Abstract
Infectious proteins (prions) in yeast or other microorganisms can be identified by genetic methods of rather general applicability. Infection in yeast means transfer by cytoplasmic mixing (cytoduction), a property of all non-chromosomal genetic elements whether plasmids, viruses, or prions. Prions can be diagnosed by reversible curability, increased occurrence when the corresponding protein is overproduced, a requirement for the gene for the corresponding protein for propagation, and, in some cases, similarity of phenotype of: (a) mutations in the gene for the protein and (b) the presence of the prion. This approach is illustrated with [URE3], an amyloid-based prion of the regulator of nitrogen catabolism, Ure2p and [PSI(+)] as a prion of the translation termination factor Sup35p. The prion concept is not limited to infectious amyloids, but includes proteins whose active form is necessary for the activation of the inactive precursor. We detail methods used in studies of [URE3] and [beta], a self-activating protease, some of which are of broad application.
MeSH terms
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Aspartic Acid / analogs & derivatives
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Aspartic Acid / metabolism
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Carboxypeptidases / chemistry
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Carboxypeptidases / metabolism
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Cathepsin A
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Gene Expression / genetics
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Glutathione Peroxidase
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Green Fluorescent Proteins / genetics
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Green Fluorescent Proteins / metabolism
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Guanidine / pharmacology
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Peptide Termination Factors
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Phenotype
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Prions / analysis*
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Prions / chemistry
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Prions / genetics
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Protein Conformation / drug effects
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / growth & development
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Saccharomyces cerevisiae / metabolism
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Saccharomyces cerevisiae Proteins / analysis*
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Saccharomyces cerevisiae Proteins / chemistry
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism
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Serine Endopeptidases / analysis*
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Serine Endopeptidases / chemistry
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Serine Endopeptidases / metabolism
Substances
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Peptide Termination Factors
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Prions
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Recombinant Fusion Proteins
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SUP35 protein, S cerevisiae
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Saccharomyces cerevisiae Proteins
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Green Fluorescent Proteins
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Aspartic Acid
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Glutathione Peroxidase
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URE2 protein, S cerevisiae
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Carboxypeptidases
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Cathepsin A
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PRC1 protein, S cerevisiae
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Serine Endopeptidases
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yeast proteinase B
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Guanidine
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ureidosuccinic acid