CTC1-STN1-TEN1 controls DNA break repair pathway choice via DNA end resection blockade

Area of Science:

• Molecular Biology
• Genetics
• Cancer Research

Background:

• DNA double-strand breaks (DSBs) are critical DNA lesions.
• DSB repair pathway choice is regulated by antagonistic factors like the 53BP1 axis and BRCA1-BARD1.
• The CTC1-STN1-TEN1 (CST) complex is a key component of the 53BP1 axis.

Purpose of the Study:

• To elucidate the role of the CST complex in regulating DNA double-strand break (DSB) repair.
• To understand the mechanisms by which CST suppresses DNA end resection.
• To investigate the implications of CST function in cancer therapy resistance.

Main Methods:

• Investigated the antagonistic activities between the 53BP1 axis and BRCA1-BARD1 in DSB repair.
• Utilized CST mutants to assess their impact on DNA end resection by EXO1 and BLM-DNA2.
• Examined the effect of CST dysfunction on BRCA1-deficient cells' response to PARP inhibitors.

Main Results:

• The CST complex suppresses DNA end resection by EXO1 and BLM-DNA2 through distinct mechanisms.
• BRCA1-BARD1 partially alleviates CST-mediated EXO1 suppression but not BLM-DNA2 restriction.
• CST mutants exhibit hyper-resection and confer resistance to PARP inhibitors in BRCA1-deficient cells.

Conclusions:

• CST plays a critical mechanistic role in determining DNA DSB repair pathway choice.
• CST dysfunction contributes to cancer therapy resistance, particularly in the context of 53BP1 axis alterations.
• These findings offer insights into therapeutic strategies targeting DNA repair pathways in cancer.