Mu insertions are repaired by the double-strand break repair pathway of Escherichia coli
Related Experiment Video
Updated: May 23, 2026
Assessment of DNA Double Strand Break Repair Activity Using High-throughput and Quantitative Luminescence-Based Reporter Assays
Published on: June 14, 2024
Sooin Jang1, Steven J Sandler, Rasika M Harshey
1Institute of Cellular and Molecular Biology, University of Texas at Austin, Austin, Texas, United States of America.
Abstract:
Mu is both a transposable element and a temperate bacteriophage. During lytic growth, it amplifies its genome by replicative transposition. During infection, it integrates into the Escherichia coli chromosome through a mechanism not requiring extensive DNA replication. In the latter pathway, the transposition intermediate is repaired by transposase-mediated resecting of the 5' flaps attached to the ends of the incoming Mu genome, followed by filling the remaining 5 bp gaps at each end of the Mu insertion. It is widely assumed that the gaps are repaired by a gap-filling host polymerase. Using the E. coli Keio Collection to screen for mutants defective in recovery of stable Mu insertions, we show in this study that the gaps are repaired by the machinery responsible for the repair of double-strand breaks in E. coli-the replication restart proteins PriA-DnaT and homologous recombination proteins RecABC. We discuss alternate models for recombinational repair of the Mu gaps.
Insights
The bacteriophage Mu integrates into E. coli DNA by repairing insertion gaps using replication restart and homologous recombination proteins, not a host polymerase. This reveals a novel DNA repair pathway for Mu transposition.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Bacteriophage Mu is a versatile genetic element, functioning as both a transposable element and a temperate bacteriophage.
- Mu DNA integrates into the Escherichia coli chromosome via a non-replicative pathway involving gap repair.
Purpose of the Study:
- To identify the specific host machinery responsible for repairing the gaps generated during Mu DNA integration.
- To challenge the prevailing assumption that host polymerases handle Mu integration gap repair.
Main Methods:
- Utilized the Escherichia coli Keio Collection to screen for mutants exhibiting defects in stable Mu insertion recovery.
- Conducted genetic screens to pinpoint host factors involved in the Mu transposition and integration process.
Main Results:
- Demonstrated that the replication restart proteins (PriA-DnaT) and homologous recombination proteins (RecABC) are essential for repairing the 5 bp gaps at Mu insertion sites.
- Ruled out the involvement of canonical gap-filling host polymerases in this specific repair pathway.
Conclusions:
- The repair of gaps during Mu integration relies on the double-strand break repair machinery in E. coli.
- This finding elucidates a novel recombinational repair mechanism for bacteriophage Mu integration.
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