Switch-like phosphorylation of WRN integrates end-resection with RAD51 metabolism at collapsed replication forks

Area of Science:

• Molecular Biology
• DNA Repair Mechanisms
• Cell Cycle Regulation

Background:

• Replication-dependent DNA double-strand breaks (DSBs) are critical DNA lesions that must be accurately repaired to maintain genomic stability.
• Homologous recombination (HR) is a major pathway for repairing DSBs, requiring end resection to initiate strand invasion.
• The WRN helicase is a key protein involved in DNA end resection and pathway choice in DSB repair, but its regulation is not fully understood.

Purpose of the Study:

• To elucidate the regulatory mechanisms controlling WRN helicase activity during DNA double-strand break repair.
• To investigate the role of specific kinase phosphorylations in WRN function and its connection to homologous recombination.
• To understand how WRN phosphorylation coordinates end resection with RAD51-mediated repair.

Main Methods:

• Investigated the ordered phosphorylation of the WRN helicase by CDK1, ATM, and ATR kinases.
• Utilized biochemical assays and cell-based studies to analyze WRN phosphorylation sites (Ser1058, Ser1141, Ser1133).
• Assessed the impact of WRN phosphorylation on long-range end resection, RAD51 foci formation, and HR repair efficiency.

Main Results:

• Established that ATM-dependent phosphorylation of WRN at Ser1058 is essential for long-range end resection.
• Demonstrated that phosphorylation at Ser1141 and dephosphorylation at Ser1133 (CDK1 site) are required for proper RAD51 foci metabolism and RAD51-dependent repair.
• Identified a complex regulatory network where ordered kinase action on WRN acts as a molecular switch for timely DNA repair.

Conclusions:

• Ordered phosphorylation of WRN by CDK1, ATM, and ATR kinases is a critical regulatory mechanism for DNA double-strand break repair.
• This kinase-mediated regulation ensures the timely execution of end resection and facilitates homologous recombination repair.
• The findings reveal a sophisticated molecular switch controlling WRN function, linking DNA end processing to the homologous recombination pathway.