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Updated: Aug 30, 2025
07:27
Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase
Published on: April 29, 2010
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Multiple mechanisms for overcoming lethal over-initiation of DNA replication.
Mary E Anderson1, Janet L Smith1, Alan D Grossman1
1Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
Molecular Microbiology
|September 2, 2022
Summary
Cellular DNA replication initiation is tightly controlled. Compensatory mechanisms, like altered elongation or initiation rates, prevent lethal over-initiation, revealing key regulatory pathways.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- DNA replication initiation is a critical regulatory step in bacterial cell division.
- The initiator protein DnaA and origin of replication (oriC) are key targets for controlling replication.
- Disruptions in replication initiation can negatively impact cell fitness.
Purpose of the Study:
- To investigate compensatory mechanisms that counteract lethal DNA replication over-initiation.
- To identify genetic suppressors of synthetic lethality in Bacillus subtilis resulting from combined replication initiation defects.
- To elucidate the role of the replicative helicase in regulating DNA replication.
Main Methods:
- Genetic analysis of Bacillus subtilis mutants.
- Characterization of suppressors restoring viability to dnaA1 ∆yabA double mutants.
- Assessing the impact of altered replication elongation and initiation rates on cell fitness.
Main Results:
- Loss of yabA (a negative regulator of initiation) combined with dnaA1 mutation caused synthetic lethality.
- Suppression of lethality was achieved by mutations stimulating replication elongation (relA, nrdR) or decreasing initiation (dnaC, cshA).
- Decreased levels of the replicative helicase (DnaC) were found to limit replication initiation, even in wild-type cells during rapid growth.
Conclusions:
- Multiple cellular mechanisms, including adjustments in replication elongation and initiation, can compensate for replication over-initiation.
- The replicative helicase (DnaC) plays a limiting role in DNA replication initiation.
- Understanding these regulatory pathways is crucial for comprehending bacterial cell cycle control.
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