A small-molecule protein-protein interaction inhibitor of PARP1 that targets its BRCT domain

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Poly(ADP-ribose)polymerase-1 (PARP1) is crucial for DNA repair and damage response.
• PARP1 is a validated cancer target, but catalytic domain inhibitors lack selectivity.
• Protein-protein interaction (PPI) inhibitors offer a more selective alternative for targeting PARP1.

Purpose of the Study:

• To develop a high-throughput assay for screening PARP1 BRCT domain PPI inhibitors.
• To identify novel small molecules that inhibit PARP1 activity via PPI disruption.
• To investigate the inhibitory mechanism of (±)-gossypol against PARP1.

Main Methods:

• Established a microplate-based high-throughput screening assay for PARP1 BRCT domain PPI inhibitors.
• Screened natural products for PARP1 inhibitory activity.
• Investigated the mechanism of action of (-)-gossypol using biochemical and cellular assays.

Main Results:

• Discovered (±)-gossypol as a novel inhibitor of PARP1 with activity in vitro and in cancer cells.
• Identified (-)-gossypol as the active enantiomer, acting as a cell-permeable small-molecule PPI inhibitor.
• Demonstrated that (-)-gossypol forms a 1:2 complex with PARP1 via reversible covalent imine linkage.

Conclusions:

• Gossypol is the first identified cell-permeable small-molecule PPI inhibitor of PARP1.
• Targeting PARP1 PPIs with gossypol offers a promising, selective strategy for cancer therapy.
• The established assay facilitates the discovery of novel PARP1-targeting PPI inhibitors.