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Structural definition is important for the propagation of the yeast [PSI+] prion.

ABSTRACT: Prions are propagated in Saccharomyces cerevisiae with remarkable efficiency, yet we know little about the structural basis of sequence variations in the prion protein that support or prohibit propagation of the prion conformation. We show that certain single-amino-acid substitutions in the prion protein Sup35 impact negatively on the maintenance of the associated prion-based [PSI(+)] trait by combining in vivo phenotypic analysis with solution NMR structural studies. A clear correlation is observed between mutationally induced conformational differences in one of the oligopeptide repeats (R2) in the N terminus of Sup35 and the relative ability to propagate [PSI(+)]. Strikingly, substitution of one of a Gly-Gly pair with highly charged residues that significantly increase structural definition of R2 lead to a severe [PSI(+)] propagation defect. These findings offer a molecular explanation for the dominant-negative effects of such psi-no-more (PNM) mutations and demonstrate directly the importance of localized structural definition in prion propagation.

SUBMITTER: Marchante R

PROVIDER: S-EPMC3679450 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

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Structural definition is important for the propagation of the yeast [PSI+] prion.

Marchante Ricardo R Rowe Michelle M Zenthon Jo J Howard Mark J MJ Tuite Mick F MF

Molecular cell 20130601 5

Prions are propagated in Saccharomyces cerevisiae with remarkable efficiency, yet we know little about the structural basis of sequence variations in the prion protein that support or prohibit propagation of the prion conformation. We show that certain single-amino-acid substitutions in the prion protein Sup35 impact negatively on the maintenance of the associated prion-based [PSI(+)] trait by combining in vivo phenotypic analysis with solution NMR structural studies. A clear correlation is obse ...[more]

PMID: 23746351

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Project description:Simple Summary DnaJB6 is a human cellular protein quality control factor that prevents diverse peptides from forming disease-associated amyloid, a highly ordered fibrous protein aggregate. DnaJB6 protects human cells, animals and yeast from toxicity caused by amyloids composed of Huntington’s-related polyglutamine, Parkinson’s-related α-synuclein, and ALS- associated TDP-43, and it cures yeast of endogenous prions (infectious amyloids). However, structurally different amyloids of one and the same prion protein, and prions composed of them, can be insensitive to anti-amyloid activity of DnaJB6. This limitation raises concerns about developing DnaJB6 as a therapeutic for amyloid diseases. Prions showing this insensitivity are highly toxic to yeast with reduced function of Sis1, a yeast protein related to DnaJB6. To begin assessing how DnaJB6 might act on amyloid in cells we tested if DnaJB6 could protect yeast from this toxicity. Although it does not eliminate the prion, it protects cells from prion toxicity, but differently than Sis1. Our work provides insight into how human DnaJB6 counteracts cellular toxicity caused by amyloid and establishes an in vivo genetic system useful for studying DnaJB6-amyloid interactions to decipher its mechanisms of action. Abstract Human J-domain protein (JDP) DnaJB6 has a broad and potent activity that prevents formation of amyloid by polypeptides such as polyglutamine, A-beta, and alpha-synuclein, related to Huntington’s, Alzheimer’s, and Parkinson’s diseases, respectively. In yeast, amyloid-based [PSI+] prions, which rely on the related JDP Sis1 for replication, have a latent toxicity that is exposed by reducing Sis1 function. Anti-amyloid activity of DnaJB6 is very effective against weak [PSI+] prions and the Sup35 amyloid that composes them, but ineffective against strong [PSI+] prions composed of structurally different amyloid of the same Sup35. This difference reveals limitations of DnaJB6 that have implications regarding its therapeutic use for amyloid disease. Here, we find that when Sis1 function is reduced, DnaJB6 represses toxicity of strong [PSI+] prions and inhibits their propagation. Both Sis1 and DnaJB6, which are regulators of protein chaperone Hsp70, counteract the toxicity by reducing excessive incorporation of the essential Sup35 into prion aggregates. However, while Sis1 apparently requires interaction with Hsp70 to detoxify [PSI+], DnaJB6 counteracts prion toxicity by a different, Hsp70-independent mechanism.

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Structural definition is important for the propagation of the yeast [PSI+] prion.

Publications

Structural definition is important for the propagation of the yeast [PSI+] prion.

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