PARP1 hyperactivity stalls translation and triggers stress granule formation following DNA damage

Cells respond to various stressors by inhibiting global translation and forming stress granules (SGs), cytoplasmic organelles enriched in certain RNA-binding proteins, and RNA. Genotoxic stress also induces SG assembly, but it is unclear how nuclear stress signals are transmitted to trigger cytoplasmic responses. We show that DNA-damaging agents that activate a nuclear poly(ADP-ribose) polymerase (PARP), PARP1, stall translation and induce SGs. We find that PARP1 activation depletes NAD+, which depletes cellular ATP, activating ATP-sensor AMPK and inhibiting mTORC1 via Raptor phosphorylation. Subsequent hypophosphorylation of 4EBP1 inhibits translation. These effects are suppressed by PAR-metabolism regulators, XRCC1, PARG, and Nudix5, and reversed by NAD+ precursor supplementation. Cells lacking SG scaffolds, G3BP1 and G3BP2, show reduced viability after genotoxic stress, which is rescued by G3BP1 overexpression. These findings link PARP1 activity to translational control and SG formation, which may protect against cell death following DNA damage. These mechanisms provide insight into PARP1- and stress granule-associated diseases, including cancer and neurodegeneration.