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Updated: May 17, 2026
07:27
Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase
Published on: April 29, 2010
Continued DNA synthesis in replication checkpoint mutants leads to fork collapse
Sarah A Sabatinos1, Marc D Green, Susan L Forsburg
1Molecular and Computational Biology, University of Southern California, Los Angeles, California, USA. sabatino@usc.edu
Molecular and Cellular Biology
|October 10, 2012
Summary
Checkpoint mutants cds1Δ and mrc1Δ show prolonged DNA synthesis and damage after hydroxyurea treatment. Replication fork collapse is a dynamic process continuing post-treatment, impacting genome replication.
Area of Science:
- Molecular Biology
- Cell Cycle Regulation
- DNA Replication and Repair
Background:
- Hydroxyurea (HU) treatment activates intra-S phase checkpoint proteins Cds1 and Mrc1 to prevent replication fork collapse.
- Understanding the dynamics of replication fork stability under genotoxic stress is crucial for cell cycle control.
Purpose of the Study:
- To investigate the consequences of impaired intra-S phase checkpoint function (cds1Δ and mrc1Δ mutants) during hydroxyurea-induced DNA replication stress.
- To characterize the process of replication fork collapse and its impact on genome replication post-HU treatment.
Main Methods:
- Utilized cds1Δ and mrc1Δ checkpoint mutants in yeast models.
- Applied hydroxyurea (HU) treatment to induce DNA replication stress.
- Measured DNA synthesis, DNA damage (phosphorylated histone H2A), and accumulation of DNA repair proteins (RPA, Rad52) using live-cell imaging and biochemical assays.
- Investigated the role of MCM helicase in DNA synthesis and RPA accumulation.
Main Results:
- cds1Δ and mrc1Δ mutants exhibited prolonged DNA synthesis in the presence of HU and after release, accompanied by increased DNA damage.
- Live-cell imaging revealed extensive accumulation of Replication Protein A (RPA) foci, followed by Rad52 foci, in mutants.
- Both DNA synthesis and RPA accumulation were dependent on the MCM helicase, indicating ongoing, albeit unstable, replication activity.
Conclusions:
- Replication fork collapse is a dynamic process initiated by accumulated DNA damage and instability, preventing further replication.
- Impaired checkpoint function in cds1Δ and mrc1Δ mutants allows replication forks to progress beyond a 'collapse point', leading to genome-wide replication defects.
- Replication fork collapse and its consequences continue even after the release from hydroxyurea treatment, highlighting the persistent nature of replication stress effects.
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