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[Identification of new genes that affect [PSI^(+)] prion toxicity in Saccharomyces cerevisiae yeast]
A G Matveenko1,2, M V Belousov1, S A Bondarev1,3
1Department of Genetics and Biotechnology, St. Petersburg State University, St. Petersburg, 199034 Russia.
Abstract:
Translation termination is an important step in gene expression. Its correct processing is governed by eRF1 (Sup45) and eRF3 (Sup35) proteins. In Saccharomyces cerevisiae, mutations in the corresponding genes, as well as Sup35 aggregation in [PSI^(+)] cells that propagate the prion form of Sup35 lead to inaccurate stop codon recognition and, consequently, nonsense suppression. The presence of stronger prion variants results in the more efficient suppression of nonsense mutations. Previously, we proposed a synthetic lethality test that enables the identification of genes that may influence either translation termination factors or [PSI^(+)] manifestation. This is based on the fact that the combination of sup45 mutations with the strong [PSI^(+)] prion variant in diploids is lethal. In this work, a set of genes that were previously shown to enhance nonsense suppression was analyzed. It was found that ABF1, FKH2, and REB1 overexpression decreased the growth of strains in a prion-dependent manner and, thus, might influence [PSI^(+)] prion toxicity. It was also shown that the synthetic lethality of [PSI^(+)] and sup45 mutations increased with the overexpression of GLN3 and MOT3 that encode Q/N-rich transcription factors. An analysis of the effects of their expression on the transcription of the release factors genes revealed an increase in SUP35 transcription in both cases. Since SUP35 overexpression is known to be toxic in [PSI^(+)] strains, these genes apparently enhance [PSI^(+)] toxicity via the regulation of SUP35 transcription.
Insights
Gene expression relies on accurate translation termination. This study identifies genes affecting prion toxicity and nonsense suppression, revealing that GLN3 and MOT3 overexpression enhances prion toxicity by increasing SUP35 transcription.
Area of Science:
- Molecular Biology
- Genetics
- Prion Biology
Background:
- Translation termination is crucial for gene expression, regulated by eRF1 (Sup45) and eRF3 (Sup35).
- Prion forms of Sup35 ([PSI^(+)]) and mutations in termination factors cause nonsense suppression, with stronger prions leading to more efficient suppression.
- A synthetic lethality test was developed to identify genes influencing translation termination factors or [PSI^(+)] prion manifestation.
Purpose of the Study:
- To analyze genes previously shown to enhance nonsense suppression.
- To investigate the influence of specific gene overexpression on [PSI^(+)] prion toxicity and synthetic lethality with sup45 mutations.
- To elucidate the mechanisms by which these genes affect prion toxicity, particularly concerning SUP35 transcription.
Main Methods:
- Utilized a synthetic lethality test combining sup45 mutations with strong [PSI^(+)] prion variants in Saccharomyces cerevisiae.
- Analyzed the effects of overexpressing genes (ABF1, FKH2, REB1, GLN3, MOT3) on strain growth in a prion-dependent manner.
- Examined the impact of GLN3 and MOT3 overexpression on the transcription of release factor genes, specifically SUP35.
Main Results:
- Overexpression of ABF1, FKH2, and REB1 decreased strain growth in a prion-dependent manner, suggesting influence on [PSI^(+)] prion toxicity.
- Overexpression of GLN3 and MOT3, encoding Q/N-rich transcription factors, increased the synthetic lethality of [PSI^(+)] and sup45 mutations.
- Both GLN3 and MOT3 overexpression led to increased SUP35 transcription.
Conclusions:
- ABF1, FKH2, and REB1 may influence [PSI^(+)] prion toxicity.
- GLN3 and MOT3 enhance [PSI^(+)] toxicity by upregulating SUP35 transcription, which is known to be toxic in [PSI^(+)] strains.
- These findings highlight the intricate relationship between transcription factors, prion biology, and the fidelity of translation termination.
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