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S-phase checkpoint protects from aberrant replication fork processing and degradation
Iván Núñez-Martín1,2, Lucy S Drury3, María I Martínez-Jiménez4
1Andalusian Center of Molecular Biology and Regenerative Medicine, Universidad de Sevilla-CSIC-Universidad Pablo de Olavide, Seville 41092, Spain.
Nucleic Acids Research
|July 30, 2025
Summary
Replication stress in cancer cells is managed by checkpoints. Our study shows DNA processing factors cause cell death by degrading nascent DNA at stalled forks, a process preventable by human PrimPol.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Replication stress is a common feature in cancer cells, necessitating robust checkpoint mechanisms to maintain genomic stability.
- The integrity of replication forks during DNA damage is critical for cell survival, yet the precise mechanisms leading to cell death in checkpoint mutants remain elusive.
Purpose of the Study:
- To elucidate the molecular mechanisms underlying replication fork instability and cell death in budding yeast checkpoint mutants exposed to DNA damage.
- To identify the specific DNA processing factors involved in the aberrant processing of stalled replication forks.
Main Methods:
- Utilized budding yeast (Saccharomyces cerevisiae) as a model organism.
- Employed genetic analysis of checkpoint mutants and DNA processing factors (Rad51, Rad5, Mus81, Exo1).
- Assessed replication fork integrity and nascent DNA degradation through molecular assays, including the impact of human PrimPol expression.
Main Results:
- Identified Rad51, Rad5 (HIRAN and helicase domains), and Mus81 catalytic activity as contributors to cell death in checkpoint mutants.
- Demonstrated that Exo1, along with the aforementioned factors, drives the degradation of nascent DNA at stalled replication forks upon DNA damage.
- Showed that expressing human PrimPol in yeast mitigates this nascent DNA degradation.
Conclusions:
- S-phase checkpoints are essential for preventing the detrimental processing of stalled replication forks during DNA damage.
- Aberrant processing by DNA processing factors leads to nascent DNA degradation and cell death in the absence of functional checkpoints.
- Safeguarding nascent DNA integrity at stalled replication forks is a critical function of S-phase checkpoints.
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