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Replication fork uncoupling causes nascent strand degradation and fork reversal

Tamar Kavlashvili1, Wenpeng Liu1, Taha M Mohamed1

  • 1Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA.

Nature Structural & Molecular Biology
|January 2, 2023
PubMed

Insights

Genotoxins trigger nascent strand degradation (NSD) and replication fork reversal by causing uncoupling. The replicative helicase remains bound during these genome stability events.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • Genotoxins induce nascent strand degradation (NSD) and replication fork reversal, processes vital for genome stability.
  • These mechanisms are targeted by chemotherapy, but their triggers and the behavior of the replicative helicase remain unclear.

Purpose of the Study:

  • To investigate the triggers and mechanisms of NSD and replication fork reversal.
  • To determine the fate of the replicative helicase during these DNA replication stress responses.

Main Methods:

  • Developed a biochemical approach using Xenopus egg extracts for synchronous, localized NSD and fork reversal studies.
  • Validated findings with experiments in human cells.

Main Results:

  • Replication fork uncoupling was shown to stimulate NSD of nascent strands and promote fork reversal.
  • The replicative helicase was observed to remain bound throughout NSD and fork reversal.
  • NSD was found to occur both before and after fork reversal, suggesting multiple degradation steps.

Conclusions:

  • Replication fork uncoupling is a key trigger for both NSD and fork reversal.
  • Elucidated critical events preceding fork reversal, including multiple NSD steps.
  • Demonstrated the persistent binding of the replicative helicase during these DNA damage responses.

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