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Updated: Aug 2, 2026
Rapid Identification of Chemical Genetic Interactions in Saccharomyces cerevisiae
Published on: April 5, 2015
Interactions of Exo1p with components of MutLalpha in Saccharomyces cerevisiae
P T Tran1, J A Simon, R M Liskay
1Department of Molecular and Medical Genetics, Oregon Health Sciences University, Portland 97201, USA.
Abstract:
Previously, we reported evidence suggesting that Saccharomyces cerevisiae MutLalpha, composed of Mlh1p and Pms1p, was a functional member of the gyrase b/Hsp90/MutL (GHL) dimeric ATPase superfamily characterized by highly conserved ATPase domains. Similar to other GHL ATPases, these putative ATPase domains of MutLalpha may be important for the recruitment and/or activation of downstream effectors. One downstream effector candidate is Exo1p, a 5'-3' double stranded DNA exonuclease that has previously been implicated in DNA mismatch repair (MMR). Here we report yeast two-hybrid results suggesting that Exo1p can interact physically with MutLalpha through the Mlh1p subunit. We also report epistasis analysis involving MutLalpha ATPase mutations combined with exo1Delta. One interpretation of our genetic results is that MutLalpha ATPase domains function to direct Exo1p and other functionally redundant exonucleases during MMR. Finally, our results show that much of the increase in spontaneous mutation observed in an exo1Delta strain is REV3-dependent, in turn suggesting that Exo1p is also involved in one or more MMR-independent mutation avoidance pathways.
Insights
Saccharomyces cerevisiae MutLalpha interacts with Exo1p, a DNA exonuclease, suggesting a role in DNA mismatch repair (MMR). Exo1p also participates in MMR-independent pathways, impacting spontaneous mutation rates.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Saccharomyces cerevisiae MutLalpha (Mlh1p and Pms1p) is part of the GHL ATPase superfamily.
- MutLalpha's ATPase domains may recruit or activate downstream effectors in DNA repair.
- Exo1p, a 5'-3' double-stranded DNA exonuclease, is a candidate effector involved in DNA mismatch repair (MMR).
Purpose of the Study:
- To investigate the physical interaction between Exo1p and MutLalpha.
- To elucidate the functional relationship between MutLalpha ATPase domains and Exo1p in MMR.
- To explore the role of Exo1p in MMR-independent mutation avoidance pathways.
Main Methods:
- Yeast two-hybrid assays to detect protein-protein interactions.
- Epistasis analysis combining MutLalpha ATPase mutations with exo1 deletion.
- Analysis of spontaneous mutation rates in mutant strains.
Main Results:
- Yeast two-hybrid results indicate Exo1p physically interacts with MutLalpha via the Mlh1p subunit.
- Epistasis analysis suggests MutLalpha ATPase domains direct Exo1p and other exonucleases during MMR.
- Increased spontaneous mutations in exo1 deletion strains are REV3-dependent, implicating Exo1p in MMR-independent pathways.
Conclusions:
- Exo1p directly interacts with MutLalpha, supporting its role as a downstream effector in DNA mismatch repair.
- MutLalpha's ATPase domains are crucial for guiding Exo1p and redundant exonucleases in MMR.
- Exo1p is involved in both MMR-dependent and MMR-independent pathways for avoiding mutations.
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