Related Experiment Video
Updated: Oct 2, 2026
Using Next Generation Sequencing to Identify Mutations Associated with Repair of a CAS9-induced Double Strand Break Near the CD4 Promoter
Published on: March 31, 2022
Suppression of genetic defects within the RAD6 pathway by srs2 is specific for error-free post-replication repair but
1Department of Microbiology and Immunology, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK S7N 5E5, Canada.
Abstract:
srs2 was isolated during a screen for mutants that could suppress the UV-sensitive phenotype of rad6 and rad18 cells. Genetic analyses led to a proposal that Srs2 acts to prevent the channeling of DNA replication-blocking lesions into homologous recombination. The phenotypes associated with srs2 indicate that the Srs2 protein acts to process lesions through RAD6-mediated post-replication repair (PRR) rather than recombination repair. The RAD6 pathway has been divided into three rather independent subpathways: two error-free (represented by RAD5 and POL30) and one error-prone (represented by REV3). In order to determine on which subpathways Srs2 acts, we performed comprehensive epistasis analyses; the experimental results indicate that the srs2 mutation completely suppresses both error-free PRR branches. Combined with UV-induced mutagenesis assays, we conclude that the Polzeta-mediated error-prone pathway is functional in the absence of Srs2; hence, Srs2 is not required for mutagenesis. Furthermore, we demonstrate that the helicase activity of Srs2 is probably required for the phenotypic suppression of error-free PRR defects. Taken together, our observations link error-free PRR to homologous recombination through the helicase activity of Srs2.
Insights
SRS2 protein prevents DNA damage from triggering homologous recombination. It processes lesions via RAD6-mediated post-replication repair (PRR), particularly error-free pathways, and its helicase activity links PRR to recombination.
Area of Science:
- Molecular biology
- DNA repair mechanisms
- Genetics
Background:
- The SRS2 gene was identified in a screen for suppressors of UV sensitivity in rad6 and rad18 mutants.
- Genetic analysis suggests SRS2's role in preventing DNA replication-blocking lesions from entering homologous recombination pathways.
- Phenotypic data indicate SRS2 processes lesions through RAD6-mediated post-replication repair (PRR) rather than recombination repair.
Purpose of the Study:
- To elucidate the specific subpathways of RAD6-mediated PRR on which SRS2 acts.
- To investigate the role of SRS2 in DNA repair and mutagenesis.
- To determine the functional requirement of SRS2's helicase activity in suppressing PRR defects.
Main Methods:
- Comprehensive epistasis analyses were performed to determine SRS2's interaction with different PRR subpathways.
- UV-induced mutagenesis assays were conducted to assess the impact of SRS2 on mutagenesis.
- Phenotypic analysis of srs2 mutants was used to evaluate its role in DNA repair.
Main Results:
- The srs2 mutation was found to completely suppress both error-free branches of PRR.
- The Polzeta-mediated error-prone pathway remains functional in the absence of SRS2, indicating SRS2 is not required for mutagenesis.
- The helicase activity of SRS2 appears essential for the phenotypic suppression of error-free PRR defects.
Conclusions:
- SRS2 acts on error-free PRR pathways, linking them to homologous recombination via its helicase activity.
- SRS2 is not essential for DNA mutagenesis, as the error-prone pathway is functional without it.
- These findings provide a mechanistic link between error-free post-replication repair and homologous recombination pathways.
Related Concept Videos
01:38Nucleotide Excision Repair
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...
01:46Nucleotide Excision Repair
01:46Nucleotide Excision Repair
01:20Mismatch Repair
The Mutator Protein Family Plays a Key Role in DNA Mismatch Repair
The human genome has more than 3 billion base pairs of DNA per cell. Prior to cell division, that vast amount of genetic...
01:48Mismatch Repair
01:48Mismatch Repair