The Oncogenic Helicase ALC1 Regulates PARP Inhibitor Potency by Trapping PARP2 at DNA Breaks

Area of Science:

• Molecular Biology
• Cancer Research
• DNA Repair

Background:

• Poly(ADP-ribose) polymerase inhibitors (PARPis) exert anti-tumor effects by trapping PARP1 on damaged chromatin.
• The role and regulation of PARP2, an isoform with overlapping functions, remain less understood.
• The mechanisms governing the release of PARP1/2 from DNA lesions are largely unknown.

Purpose of the Study:

• To investigate the impact of PARPis on PARP2.
• To identify molecular machines involved in PARP1/2 release from DNA lesions.
• To explore the therapeutic potential of targeting PARP2-ALC1 interactions.

Main Methods:

• Utilized PARP inhibitors (PARPis) in cellular models.
• Assessed PARP1 and PARP2 trapping on chromatin.
• Investigated the role of the helicase ALC1 (CHD1L) in PARP2 release.
• Examined the effects of ALC1 manipulation on DNA damage response and cell viability.

Main Results:

• PARPis robustly trap PARP2, similar to PARP1.
• The helicase ALC1 is essential for the release of PARP2 from DNA lesions.
• Catalytic inactivation of ALC1 leads to quantitative trapping of PARP2, but not PARP1.
• ALC1 manipulation impacts responses to single-strand DNA breaks via PARP2 trapping.
• ALC1 activity potentiates PARPi-induced cancer cell killing and mediates synthetic lethality in BRCA-deficient cells.

Conclusions:

• The chromatin remodeler ALC1 actively facilitates PARP2 turnover from DNA lesions.
• PARP2 contributes significantly to cellular responses to PARPis.
• Targeting ALC1's ATP-dependent remodeling activity may offer novel therapeutic strategies for cancer by selectively inhibiting PARP DNA repair functions.