PLK1 regulates the PrimPol damage tolerance pathway during the cell cycle

Area of Science:

• Molecular Biology
• Cell Cycle Regulation
• DNA Replication and Repair

Background:

• Replication stress and DNA damage can stall DNA replication forks, hindering genome synthesis.
• Damage tolerance pathways, including repriming by Primase-Polymerase (PrimPol), are crucial for bypassing DNA lesions during S phase.
• The regulatory mechanisms governing PrimPol activity remain largely unelucidated.

Purpose of the Study:

• To investigate the regulatory mechanisms controlling Primase-Polymerase (PrimPol) function.
• To determine the role of Polo-like kinase 1 (PLK1) in PrimPol regulation.
• To assess the consequences of dysregulated PrimPol activity on genomic stability.

Main Methods:

• Investigated the phosphorylation of PrimPol by Polo-like kinase 1 (PLK1) at a conserved residue.
• Analyzed cell cycle-dependent phosphorylation patterns of PrimPol.
• Assessed the impact of PLK1 inhibition on PrimPol recruitment, replication stress response, and genomic integrity using various genotoxic treatments.

Main Results:

• Demonstrated that PLK1 phosphorylates PrimPol at a key residue, modulating its chromatin recruitment throughout the cell cycle.
• Showed that this phosphorylation is dynamically regulated in response to replication stress.
• Found that loss of PLK1-dependent PrimPol regulation results in chromosome breaks, micronuclei formation, and decreased cell survival following exposure to camptothecin, olaparib, and UV-C radiation.

Conclusions:

• PLK1-mediated phosphorylation is a critical regulator of PrimPol activity, ensuring proper repriming during DNA replication stress.
• Aberrant repriming due to loss of PLK1 regulation leads to significant genomic instability.
• These findings underscore the importance of precise regulation of DNA damage tolerance pathways for maintaining genome integrity.