A local ATR-dependent checkpoint pathway is activated by a site-specific replication fork block in human cells

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• DNA replication forks can stall when encountering DNA lesions.
• The ATR-dependent intra-S checkpoint pathway is crucial for detecting and processing stalled replication forks to maintain genomic integrity.
• The precise response to a single replication fork barrier (RFB) remains poorly understood.

Purpose of the Study:

• To investigate the cellular response to a single, site-specific replication fork barrier.
• To determine whether a single RFB activates a local or global DNA damage checkpoint response.

Main Methods:

• Utilized the Escherichia coli Tus-Ter system in human MCF7 cells to create a site-specific RFB.
• Monitored the activation of the ATR-dependent checkpoint pathway.
• Assessed the phosphorylation and accumulation of γH2AX at the site of stalling.

Main Results:

• The Tus-Ter system efficiently created a site-specific RFB.
• A single RFB was sufficient to activate a localized ATR-dependent checkpoint response.
• Phosphorylation and accumulation of γH2AX were confined to within a kilobase of the RFB site.
• Global checkpoint activation was not observed.

Conclusions:

• A model of local management of replication fork stalling is supported.
• Localized checkpoint activation allows replication to proceed at other sites without delay.
• This localized response is critical for maintaining genomic integrity during replication stress.