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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

The DNA Replication Fork

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 DNA Replication Fork

The DNA Replication Fork

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...

Homologous Recombination

Homologous Recombination

The basic reaction of homologous recombination (HR) involves two chromatids that contain DNA sequences sharing a significant stretch of identity. One of these sequences uses a strand from another as a template to synthesize DNA in an enzyme-catalyzed reaction. The final product is a novel amalgamation of the two substrates. To ensure an accurate recombination of sequences, HR is restricted to the S and G2 phases of the cell cycle. At these stages, the DNA has been replicated already and the...

Translesion DNA Polymerases

Translesion DNA Polymerases

Translesion (TLS) polymerases rescue stalled DNA polymerases at sites of damaged bases by replacing the replicative polymerase and installing a nucleotide across the damaged site. Doing so, TLS allows additional time for the cell to repair the damage before resuming regular DNA replication.
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...

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Updated: Jul 19, 2026

Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase

Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase

Published on: April 29, 2010

Deregulated replication licensing causes DNA fragmentation consistent with head-to-tail fork collision.

Iain F Davidson¹, Anatoliy Li, J Julian Blow

¹School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom.

|November 4, 2006

Summary

Overexpressing the licensing protein Cdt1 causes DNA rereplication and fragmentation. This uncontrolled DNA replication triggers cell cycle checkpoints, leading to DNA damage.

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Detection of Homologous Recombination Intermediates via Proximity Ligation and Quantitative PCR in Saccharomyces cerevisiae

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Last Updated: Jul 19, 2026

Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase

Direct Restart of a Replication Fork Stalled by a Head-On RNA Polymerase

Published on: April 29, 2010

Detection of Homologous Recombination Intermediates via Proximity Ligation and Quantitative PCR in Saccharomyces cerevisiae

Detection of Homologous Recombination Intermediates via Proximity Ligation and Quantitative PCR in Saccharomyces cerevisiae

Published on: September 11, 2022

Area of Science:

Cell Biology
Molecular Biology
Genetics

Background:

The cell cycle relies on precise DNA replication to prevent genetic instability.
The replication licensing system, involving proteins like Cdt1, strictly controls DNA duplication.
Dysregulation of Cdt1 can lead to DNA rereplication, a critical event in cell cycle control.

Purpose of the Study:

To investigate the consequences of deregulating the DNA replication licensing system.
To examine the effects of Cdt1 overexpression on cell cycle progression and DNA integrity.
To understand the mechanisms underlying DNA fragmentation induced by uncontrolled rereplication.

Main Methods:

Utilizing Xenopus egg extracts for in vitro studies.
Adding recombinant Cdt1 to induce deregulation of the licensing system.
Analyzing DNA integrity and cell cycle checkpoint activation.

Main Results:

Cdt1 overexpression leads to DNA rereplication and activation of cell cycle checkpoints.
Uncontrolled rereplication, but not a single round, causes significant DNA fragmentation.
Generated DNA fragments consist solely of rereplicated DNA and suggest replication fork collisions.

Conclusions:

Cdt1-induced DNA rereplication triggers potent checkpoint responses.
DNA fragmentation observed is a direct consequence of uncontrolled rereplication, likely due to colliding replication forks.
Maintaining proper regulation of the replication licensing system is crucial for genomic stability.