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Genetic interactions between error-prone and error-free postreplication repair pathways in Saccharomyces cerevisiae
1Department of Microbiology and Immunology, University of Saskatchewan, Saskatoon, Canada. xiaow@sask.usask.ca
Abstract:
Evidence obtained from recent studies supports the existence of an error-free postreplication repair (PRR) and a mutagenesis pathway within the Saccharomyces cerevisiae RAD6 DNA repair group. The MMS2 gene is the only known yeast gene involved in error-free PRR that, when mutated, significantly increases the spontaneous mutation rate. In this study, the mutational spectrum of the mms2 mutator was determined and compared to the wild type strain. In addition, mutagenenic effects and genetic interactions of the mms2 mutator and rev3 anti-mutator were examined with respect to forward mutations, frameshift reversions as well as amber and ochre suppressions. It was concluded from these results that the mms2 mutator phenotype is largely dependent on the functional REV3 gene. The synergistic effects of mms2 and rev3 mutations towards killing by a variety of DNA-damaging agents ruled out the possibility that MMS2 simply acts to suppress REV3 activity and favored the hypothesis that MMS2 and REV3 form two alternative subpathways within the RAD6 DNA repair pathway. Taken together, we propose that two pathways represented by MMS2 and REV3 deal with a similar range of endogenous and environmental DNA damage but with different biological consequences, namely, error-free repair and mutagenesis, respectively.
Insights
The MMS2 gene in yeast plays a crucial role in error-free DNA repair. Mutations in MMS2, when interacting with REV3, suggest two distinct DNA repair pathways, error-free (MMS2) and mutagenic (REV3).
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The Saccharomyces cerevisiae RAD6 DNA repair group includes error-free postreplication repair (PRR) and mutagenesis pathways.
- The MMS2 gene is essential for error-free PRR; its mutation elevates spontaneous mutation rates.
Purpose of the Study:
- To investigate the mutational spectrum of the mms2 mutator.
- To examine the mutagenic effects and genetic interactions between mms2 and rev3 mutations.
- To elucidate the roles of MMS2 and REV3 in DNA repair pathways.
Main Methods:
- Comparative analysis of mutational spectra between mms2 mutator and wild-type yeast strains.
- Assessment of mutagenic effects and genetic interactions concerning forward mutations, frameshift reversions, and suppressions (amber, ochre).
- Evaluation of synergistic effects of mms2 and rev3 mutations on cell survival following DNA damage.
Main Results:
- The mms2 mutator phenotype is significantly influenced by the functional REV3 gene.
- Synergistic effects of mms2 and rev3 mutations on cell killing by DNA-damaging agents were observed.
- Evidence supports MMS2 and REV3 as components of alternative subpathways within the RAD6 DNA repair pathway.
Conclusions:
- MMS2 and REV3 function in two distinct subpathways of the RAD6 DNA repair pathway.
- These pathways, represented by MMS2 (error-free) and REV3 (mutagenesis), handle similar DNA damage but yield different outcomes.
- MMS2 does not merely suppress REV3 activity; they represent parallel repair mechanisms.