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Updated: Jul 13, 2026
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Published on: September 17, 2020
Inactivation of NMD increases viability of sup45 nonsense mutants in Saccharomyces cerevisiae
Svetlana Chabelskaya1, Valentina Gryzina, Svetlana Moskalenko
1Department of Genetics and Breeding, St Petersburg State University, Universitetskaya emb, 7/9, 199034, St Petersburg, Russia. shabels@mail.ru
Background:
The nonsense-mediated mRNA decay (NMD) pathway promotes the rapid degradation of mRNAs containing premature termination codons (PTCs). In yeast Saccharomyces cerevisiae, the activity of the NMD pathway depends on the recognition of the PTC by the translational machinery. Translation termination factors eRF1 (Sup45) and eRF3 (Sup35) participate not only in the last step of protein synthesis but also in mRNA degradation and translation initiation via interaction with such proteins as Pab1, Upf1, Upf2 and Upf3.
Results:
In this work we have used previously isolated sup45 mutants of S. cerevisiae to characterize degradation of aberrant mRNA in conditions when translation termination is impaired. We have sequenced his7-1, lys9-A21 and trp1-289 alleles which are frequently used for analysis of nonsense suppression. We have established that sup45 nonsense and missense mutations lead to accumulation of his7-1 mRNA and CYH2 pre-mRNA. Remarkably, deletion of the UPF1 gene suppresses some sup45 phenotypes. In particular, sup45-n upf1Delta double mutants were less temperature sensitive, and more resistant to paromomycin than sup45 single mutants. In addition, deletion of either UPF2 or UPF3 restored viability of sup45-n double mutants.
Conclusion:
This is the first demonstration that sup45 mutations do not only change translation fidelity but also acts by causing a change in mRNA stability.
Insights
Mutations in the translation termination factor Sup45 in yeast impact mRNA stability. Deleting UPF genes partially rescues these sup45 defects, revealing a link between translation termination and mRNA decay.
Area of Science:
- Molecular Biology
- Yeast Genetics
Background:
- Nonsense-mediated mRNA decay (NMD) pathway degrades mRNAs with premature termination codons (PTCs).
- Translation termination factors eRF1 (Sup45) and eRF3 (Sup35) are involved in protein synthesis, mRNA degradation, and translation initiation.
Purpose of the Study:
- To investigate the role of translation termination factor Sup45 in mRNA degradation.
- To characterize the impact of sup45 mutations on mRNA stability in Saccharomyces cerevisiae.
Main Methods:
- Sequencing of specific yeast alleles (his7-1, lys9-A21, trp1-289).
- Analysis of mRNA accumulation in sup45 mutants.
- Genetic analysis of double mutants involving UPF genes (UPF1, UPF2, UPF3).
Main Results:
- Sup45 mutations lead to the accumulation of specific mRNAs (his7-1 and CYH2 pre-mRNA).
- Deletion of UPF1 suppressed some sup45 phenotypes, including temperature sensitivity and paromomycin resistance.
- Deletion of UPF2 or UPF3 restored viability in sup45-n double mutants.
Conclusions:
- Sup45 mutations affect not only translation fidelity but also mRNA stability.
- This study demonstrates a novel role for translation termination factors in regulating mRNA decay pathways.
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