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Restarting Stalled Replication Forks

Restarting Stalled Replication Forks

DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart, a...

Restarting Stalled Replication Forks

Restarting Stalled Replication Forks

DNA replication is initiated at sites containing predefined DNA sequences known as origins of replication. DNA is unwound at these sites by the minichromosome maintenance (MCM) helicase and other factors such as Cdc45 and the associated GINS complex.The unwound single strands are protected by replication protein A (RPA) until DNA polymerase starts synthesizing DNA at the 5’ end of the strand in the same direction as the replication fork. To prevent the replication fork from falling apart, a...

The DNA Replication Fork

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An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped active region where two strands of DNA are separated and replicated continuously. The coupling of DNA unzipping and complementary strand synthesis is a characteristic feature of a replication fork. Organisms with small circular DNA, such as E. coli, often have a single origin of replication; therefore, they have only two replication forks, one in...

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An organism’s genome needs to be duplicated in an efficient and error-free manner for its growth and survival. The replication fork is a Y-shaped active region where two strands of DNA are separated and replicated continuously. The coupling of DNA unzipping and complementary strand synthesis is a characteristic feature of a replication fork. Organisms with small circular DNA, such as E. coli, often have a single origin of replication; therefore, they have only two replication forks, one in...

The Spindle Assembly Checkpoint

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The spindle assembly checkpoint is a molecular surveillance mechanism ensuring the fidelity of chromosome segregation during anaphase. The checkpoint monitors the completion of all the prerequisite steps before chromosome segregation to determine whether the segregation process should proceed or be delayed.
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...

The Spindle Assembly Checkpoint

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The spindle assembly checkpoint is a molecular surveillance mechanism ensuring the fidelity of chromosome segregation during anaphase. The checkpoint monitors the completion of all the prerequisite steps before chromosome segregation to determine whether the segregation process should proceed or be delayed.
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Related Experiment Video

Updated: Jun 25, 2026

Strand-Specific Analysis of Proteins at Replicating DNA Strands by Enrichment and Sequencing of Protein-Associated Nascent DNA Method

Strand-Specific Analysis of Proteins at Replicating DNA Strands by Enrichment and Sequencing of Protein-Associated Nascent DNA Method

Published on: May 2, 2025

Claspin and Chk1 regulate replication fork stability by different mechanisms.

Jennifer Scorah¹, Clare H McGowan

¹Department of Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.

Cell Cycle (Georgetown, Tex.)

|March 10, 2009

Summary

Claspin protein regulates DNA replication fork stability independently of its role in Chk1 activation. This finding reveals a novel function for Claspin in maintaining genomic integrity during DNA replication.

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Strand-Specific Analysis of Proteins at Replicating DNA Strands by Enrichment and Sequencing of Protein-Associated Nascent DNA Method

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Area of Science:

Molecular Biology
Cell Biology
Genetics

Background:

Claspin is a checkpoint mediator protein crucial for DNA replication by facilitating Chk1 phosphorylation and activation by ATR.
Physical association of Claspin with replication factors suggests potential roles beyond Chk1 activation.

Purpose of the Study:

To investigate the functions of Chk1 and Claspin at individual replication forks.
To determine if Claspin's functions in DNA replication are independent of Chk1.

Main Methods:

DNA combing was employed to analyze replication fork dynamics.
Comparative analysis of Chk1 and Claspin functions in unperturbed mammalian cells.

Main Results:

Claspin, similar to Chk1, regulates replication fork stability and density.
Claspin's role in fork stability is independent of the Cdc25-Cdk2 pathway, unlike Chk1's primary function.
Chk1 primarily regulates origin firing via the Cdk2-Cdc25 pathway.

Conclusions:

Claspin possesses a Chk1-independent function in regulating DNA replication fork stability.
This study supports a model where Claspin contributes to genomic stability through mechanisms distinct from Chk1 phosphorylation.