The TIP60-ATM axis regulates replication fork stability in BRCA-deficient cells

Area of Science:

• Molecular Biology
• Genetics
• DNA Repair

Background:

• Replication fork stability is crucial for genome integrity.
• Stalled forks can be reversed by translocases like SMARCAL1 and degraded if not protected by the BRCA pathway.
• ATM and ATR kinases are key regulators of DNA damage response.

Purpose of the Study:

• To investigate the role of the TIP60-ATM pathway in replication fork reversal.
• To identify genetic factors influencing cellular sensitivity to ATM inhibitors in wild-type and BRCA2-knockout cells.

Main Methods:

• Investigated the TIP60-ATM pathway's role in recruiting SMARCAL1 to stalled forks.
• Conducted genome-wide CRISPR knockout screens to assess sensitivity to ATM inhibitors.
• Validated top genetic hits from screens in both wild-type and BRCA2-knockout cells.

Main Results:

• The TIP60-ATM pathway promotes replication fork reversal by recruiting SMARCAL1, leading to degradation in BRCA-deficient cells.
• ATM activity in fork reversal is distinct from ATR.
• Identified common genes regulating responses to multiple ATM inhibitors.
• Discovered that DNA repair genes (RAD17, MDC1, USP28) are essential for survival upon ATM inhibition in BRCA2-knockout cells, unlike in wild-type cells.

Conclusions:

• The TIP60-ATM pathway plays a specific role in replication fork reversal and degradation, particularly in BRCA-deficient cells.
• ATM inhibitors exhibit differential efficacy based on BRCA status, with DNA repair pathways being critical in BRCA2-deficient contexts.
• Findings may inform the clinical use of ATM inhibitors, especially for BRCA-mutated cancers.