Ski2-like helicase ASCC3 unwinds DNA upon fork stalling to control replication stress responses

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• The activating signal co-integrator 1 complex subunit 3 (ASCC3) is a multifunctional protein with an incompletely understood role in DNA replication stress.
• Understanding ASCC3's function during replication stress is critical for comprehending genomic stability mechanisms.

Purpose of the Study:

• To elucidate the role of ASCC3 in DNA replication stress response pathways.
• To investigate the recruitment mechanism of ASCC3 to stalled replication forks.
• To determine the functional consequences of ASCC3 activity on genomic integrity.

Main Methods:

• Investigated ASCC3 recruitment to stalled replication forks.
• Analyzed ASCC3's DNA unwinding activity in vitro.
• Examined the impact of ASCC3 on SMARCAL1 recruitment, fork progression, and degradation.
• Assessed ASCC3's role in RPA accumulation and ATR activation.
• Studied ASCC3's effect on RAD51-mediated recombination and chromosome stability.

Main Results:

• ASCC3 is recruited to stalled forks via ASCC2, dependent on PCNA ubiquitylation.
• ASCC3's DNA unwinding activity is essential for SMARCAL1 recruitment and fork stabilization, particularly in BRCA1/BRCA2-deficient cells.
• ASCC3 promotes RPA accumulation, enhances ATR activation, antagonizes RAD51, and prevents chromosomal aberrations.
• ASCC3 activity suggests a role in promoting fork reversal and remodeling gap-containing fork substrates.

Conclusions:

• ASCC3 plays a multifaceted role in managing DNA replication stress.
• ASCC3 is a key regulator of multiple replication stress responses, essential for maintaining genomic stability.
• The findings highlight ASCC3 as a critical factor in preventing DNA breaks and ensuring proper chromosome segregation.