Article

Aneuploidy causes proteotoxic stress in yeast

Koch Institute for Integrative Cancer Research, Department of Biology, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02138, USA
Genes & development (Impact Factor: 12.64). 12/2012; 26(24). DOI: 10.1101/gad.207407.112
Source: PubMed

ABSTRACT Gains or losses of entire chromosomes lead to aneuploidy, a condition tolerated poorly in all eukaryotes analyzed to date. How aneuploidy affects organismal and cellular physiology is poorly understood. We found that aneuploid budding yeast cells are under proteotoxic stress. Aneuploid strains are prone to aggregation of endogenous proteins as well as of ectopically expressed hard-to-fold proteins such as those containing polyglutamine (polyQ) stretches. Protein aggregate formation in aneuploid yeast strains is likely due to limiting protein quality-control systems, since the proteasome and at least one chaperone family, Hsp90, are compromised in many aneuploid strains. The link between aneuploidy and the formation and persistence of protein aggregates could have important implications for diseases such as cancer and neurodegeneration.

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    • "Thus, proteome composition and the relative stoichiometries of proteins change dramatically during aging, presumably impeding overall proteostasis. A similar mechanism of proteostasis impairment has been suggested to occur as a result of aneuploidy (Oromendia et al., 2012; Stingele et al., 2012). Changes in transcript levels previously observed during aging (Budovskaya et al., 2008; Golden and Melov, 2004) contribute to the changes in protein abundance observed here, but the overall correlation is only moderate (R = 0.3) (Figure S1C). "
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    • "Finally, aneuploid cells exhibit phenotypes characteristic of the disruption of protein homeostasis. Aneuploid yeast and mammalian cells harbor higher levels of protein aggregates and exhibit sensitivity to compounds that interfere with protein folding and turnover (Torres et al., 2007, 2010; Tang et al., 2011; Oromendia et al., 2012; Stingele et al., 2012; Donnelly et al., 2014). Here we investigate the molecular basis of one consequence of aneuploidy—genome instability. "
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    ABSTRACT: Genetic instability is a hallmark of aneuploidy in budding and fission yeast. All aneuploid yeast strains analyzed to date harbor elevated levels of Rad52-GFP foci, a sign of DNA damage. Here we investigate how continuously elevated levels of DNA damage impact aneuploid cells. We show that Rad52-GFP foci form during S phase, consistent with the observation that DNA replication initiation and elongation are impaired in some aneuploid yeast strains. We furthermore find that although DNA damage is low in aneuploid cells, it nevertheless has dramatic consequences. Many aneuploid yeast strains adapt to DNA damage and undergo mitosis despite the presence of unrepaired DNA leading to cell death. Wild-type cells exposed to low levels of DNA damage exhibit a similar phenotype indicating that adaptation to low levels of unrepaired DNA is a general property of the cell's response to DNA damage. Our results indicate that by causing low levels of DNA damage, whole chromosome aneuploidies lead to DNA breaks that persist into mitosis. Such breaks are the substrate for translocations and deletions that are a hallmark of cancer. © 2015 by The American Society for Cell Biology.
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    • "Previously, it was shown that a loss-of-function mutation in the gene encoding the deubiquitinating enzyme Ubp6 also markedly alleviated the negative effects of aneuploidy including impaired proliferation and accumulation of cytoplasmic protein deposits in budding yeast (Torres et al, 2010; Oromendia et al, 2012). Here, we have identified the first aneuploidy-tolerating genetic modification in human cells. "
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    ABSTRACT: Aneuploidy is a hallmark of cancer and is associated with malignancy and poor prognosis. Recent studies have revealed that aneuploidy inhibits proliferation, causes distinct alterations in the transcriptome and proteome and disturbs cellular proteostasis. However, the molecular mechanisms underlying the changes in gene expression and the impairment of proteostasis are not understood. Here, we report that human aneuploid cells are impaired in HSP90-mediated protein folding. We show that aneuploidy impairs induction of the heat shock response suggesting that the activity of the transcription factor heat shock factor 1 (HSF1) is compromised. Indeed, increased levels of HSF1 counteract the effects of aneuploidy on HSP90 expression and protein folding, identifying HSF1 overexpression as the first aneuploidy-tolerating mutation in human cells. Thus, impaired HSF1 activity emerges as a critical factor underlying the phenotypes linked to aneuploidy. Finally, we demonstrate that deficient protein folding capacity directly shapes gene expression in aneuploid cells. Our study provides mechanistic insight into the causes of the disturbed proteostasis in aneuploids and deepens our understanding of the role of HSF1 in cytoprotection and carcinogenesis.
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