Topological stress regulates replication fork dynamics in unperturbed S phase

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Accurate genome duplication is essential for cell viability.
• Replication fork progression requires tight regulation.
• Disruptions in DNA replication contribute to genomic instability.

Purpose of the Study:

• To elucidate the mechanisms controlling replication fork dynamics during unperturbed S-phase.
• To investigate the role of Topoisomerase IIA (TOP2A) in regulating replication fork speed.
• To understand the link between TOP2A, torsional stress, and DNA replication stress.

Main Methods:

• Analysis of replication fork elongation rates in early and late S-phase.
• Investigating the impact of TOP2A levels on replication fork dynamics.
• Assessing ATR-CHK1 signaling activation under varying TOP2A conditions.
• Evaluating the effect of TOP2A overexpression on oncogene-induced replication stress.

Main Results:

• Replication forks elongate slower in early S-phase and faster in late S-phase.
• Elevated origin firing and low TOP2A in early S-phase induce torsional stress, leading to replisome uncoupling and reduced fork speed.
• TOP2A overexpression enhances fork speed and mitigates replication stress in early S-phase.
• TOP2A overexpression suppresses oncogene-driven replication stress.

Conclusions:

• TOP2A acts as a limiting replication factor during unperturbed early S-phase.
• Basal ATR-CHK1 signaling is triggered by transient replisome uncoupling.
• TOP2A upregulation in cancer may serve as a compensatory mechanism against oncogene-induced replication stress.
• TOP2A is a key regulator of replication fork dynamics.