The BRCA1- RAD51 Axis Regulates SCAI/REV3 Dependent Replication Fork Maintenance.

Area of Science:

• Molecular Biology
• Genetics
• Cancer Research

Background:

• Replication stress is a major cause of genomic instability and cancer.
• BRCA1 is known to protect stalled replication forks from degradation.
• The precise mechanisms by which BRCA1 facilitates fork restoration remain incompletely understood.

Purpose of the Study:

• To investigate the fork protection-independent role of BRCA1 in stalled replication fork restoration.
• To elucidate the involvement of SCAI and REV3 in BRCA1-mediated fork repair.
• To understand the impact of SCAI/REV3 loss on DNA break formation and genomic stability.

Main Methods:

• Domain analysis of BRCA1.
• Assessment of DNA break formation and fork reversal.
• Investigation of RAD51 regulation.
• Analysis of cell death and genomic instability upon DNA damage.

Main Results:

• BRCA1 drives stalled fork restoration via RAD51 regulation, dependent on SCAI and REV3.
• BRCA1 induces SLX4-mediated DNA breaks in the absence of SCAI/REV3, which are necessary for repair synthesis and restart.
• Loss of SCAI/REV3 leads to persistent DNA breaks, increased genomic instability, and cell death.
• BRCA1's role in fork breakage requires its coiled-coil domain and is distinct from its role in double-strand break resection.

Conclusions:

• BRCA1 has a critical role in stalled replication fork restoration independent of its fork protection function.
• SCAI and REV3 are essential for repair synthesis and restart of stalled forks, particularly in the context of BRCA1-mediated DNA break formation.
• Loss of SCAI/REV3 function results in significant DNA damage, genomic instability, and cell death, highlighting their importance in maintaining genome integrity during replication stress.