Protein isolation and Western blot analysis

Cell lysates were prepared in RIPA lysis buffer supplemented with complete EDTA-Free Protease Inhibitor Cocktail (Sigma-Aldrich), 1 mM NaF, and 2 mM Na₃VO₄. Proteins were resolved in 10% SDS-PAGE gels and transferred onto a 0.45 µm nitrocellulose membrane (Bio-Rad). Membranes were blocked with 5% non-fat milk and incubated with primary antibodies at 4°C overnight, followed by secondary antibodies LI-COR IRDye 800CW goat anti-Mouse (#926-32210, 1:15,000 dilution) or LI-COR IRDye 680RD goat anti-Rabbit (#926- 68071, 1:15,000 dilution) and scanned on LI-COR Odyssey CLx (Lincoln, NE). At least two independent immunoblots were performed for each experiment, with a representative immunoblot shown. Relative PARP cleavage was calculated using the formula:

Antibodies are listed in Supplementary Table S3.