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Replication restart in gyrB Escherichia coli mutants
Gianfranco Grompone1, S Dusko Ehrlich, Bénédicte Michel
1Laboratoire de Génétique Microbienne, Institut National de la Recherche Agronomique, 78352 Jouy en Josas, France.
Molecular Microbiology
|April 16, 2003
Summary
Bacterial DNA gyrase mutants require the preprimosomal protein PriA for viability. Replication restart in these gyrase-affected strains depends on PriA-dependent primosome assembly, not homologous recombination.
Area of Science:
- Bacteriology
- Molecular Biology
- Genetics
Background:
- DNA gyrase is a crucial bacterial topoisomerase that manages DNA supercoiling.
- Altered gyrase activity can impede DNA replication, necessitating mechanisms for restart.
Purpose of the Study:
- To investigate the role of replication restart pathways in bacterial viability under conditions of impaired DNA gyrase activity.
- To determine the specific requirements for replication restart in gyrase mutants.
Main Methods:
- Utilized two partial loss-of-function gyrase (gyrB) mutants.
- Examined the essentiality of the preprimosomal protein PriA and its helicase function.
- Investigated the impact of dnaC809 and DeltatopA mutations on gyrB priA double mutants.
- Assessed the role of homologous recombination in gyrase mutant viability.
Main Results:
- PriA is essential for the viability of gyrB mutants; its helicase function is not required.
- Lethality in gyrB priA double mutants is suppressed by dnaC809, indicating a need for primosome assembly.
- The co-lethality of gyrB and priA mutations is independent of DNA supercoiling levels.
- Inactivation of homologous recombination does not affect gyrB mutant viability.
Conclusions:
- Replication restart in gyrase mutants is independent of homologous recombination.
- Replication forks disassemble when blocked by positive supercoils in gyrase mutants.
- Restart occurs via PriA-dependent primosome assembly directly on inactivated replication forks.