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S. cerevisiae has three pathways for DNA interstrand crosslink repair
K F Grossmann1, A M Ward, M E Matkovic
1Department of Molecular and Medical Genetics, Oregon Health Sciences University, Mail Code L103, 3181 SW Sam Jackson Park Road, Portland, OR 97201, USA.
Mutation Research
|December 12, 2001
Summary
Yeast mutants reveal three distinct DNA repair pathways for interstrand crosslinks (ICLs). Disrupting these pathways, SNM1, REV3, and RAD51, individually or combined, leads to increased sensitivity, with a triple mutant being lethal.
Area of Science:
- * Molecular Biology
- * Genetics
- * DNA Repair Mechanisms
Background:
- * Interstrand crosslinks (ICLs) are severe DNA lesions requiring efficient repair.
- * Previous studies identified yeast mutants sensitive to ICLs, including snm1, rev3, and rad51.
- * The specific roles and interactions of these genes in ICL repair pathways were not fully elucidated.
Purpose of the Study:
- * To investigate the genetic interactions and epistasis relationships of SNM1, REV3, and RAD51 in ICL repair.
- * To determine the number of independent ICL repair pathways in Saccharomyces cerevisiae.
- * To explore the role of S-phase delay in response to ICL damage and its relation to repair mechanisms.
Main Methods:
- * Construction and analysis of single, double, and triple yeast mutants (snm1, rev3, rad51).
- * Assessment of mutant sensitivity to ICL-inducing agents like cisplatin (CDDP) and 8-methoxypsoralen (8-MOP).
- * Observation of S-phase progression in response to DNA damage using flow cytometry.
Main Results:
- * Double and triple mutants exhibited significantly higher sensitivity to ICLs than single mutants, indicating separate epistasis groups.
- * A triple mutant (snm1 Delta rev3 Delta rad51 Delta) was lethal with one ICL per genome, suggesting three essential ICL repair pathways.
- * No S-phase delay was observed in response to ICLs in G1-phase, even in mutants deficient in nucleotide excision repair (rad14 Delta), suggesting repair is not solely dependent on rapid excision.
Conclusions:
- * Saccharomyces cerevisiae possesses three distinct and essential pathways for repairing interstrand crosslinks.
- * The study identifies SNM1, REV3, and RAD51 as key components of these separate ICL repair pathways.
- * Normal S-phase progression in the presence of ICLs is not mediated by rapid excision repair, and Pol eta is not critical for ICL resistance.