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Lethal effect of lambda DNA terminase in recombination deficient Escherichia coli
1Department of Medical Genetics, University of Toronto, Ontario, Canada.
Summary
Bacteriophage lambda DNA terminase cleaves DNA at specific sites. Host factors RecA and RecB, involved in DNA repair, prevent terminase-induced cell death by repairing broken chromosomes.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Lambda DNA terminase enzyme is crucial for phage DNA maturation.
- DNA cleavage occurs at the cos site.
- Host factors Integration Host Factor (IHF) and Terminase Host Factor (THF) are involved in vitro.
Purpose of the Study:
- To investigate the in vivo role of host proteins in lambda DNA maturation.
- To identify host mutants unable to support cos cleavage.
Main Methods:
- Developed a selection strategy for host mutants resistant to terminase-induced killing.
- Utilized chromosomally located cos sites for selection.
- Assessed susceptibility to terminase killing in recA, recB, and recD mutant strains.
Main Results:
- Lambda DNA terminase kills cells with chromosomal cos sites if they are defective in recA or recB genes.
- RecA and RecB proteins are essential for repairing terminase-induced DNA breaks.
- recD mutants, despite encoding a subunit of Exonuclease V, did not show increased susceptibility.
Conclusions:
- RecA and RecB proteins play a critical role in preventing terminase-mediated cell death in vivo.
- These host factors likely function by repairing chromosome breaks induced by terminase activity.
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