Targeting ZDHHC12-mediated PARP1 palmitoylation potentiates PARP inhibitor cytotoxicity

Poly(ADP-ribose) polymerase inhibitors (PARPi) elicit cytotoxicity by trapping PARP1 at DNA lesions, but clinical resistance remains a major challenge. Here, we identify reversible S-palmitoylation as a negative regulator of PARP1 chromatin engagement. Mass spectrometry reveals PARP1 palmitoylation at conserved cysteines within its DNA-binding domains. DNA damage reduces PARP1 palmitoylation, enhancing DNA binding, whereas inhibition of depalmitoylases APT1/2 elevates palmitoylation and suppresses DNA binding. The palmitoyltransferase ZDHHC12 catalyzes PARP1 palmitoylation, and its inhibition, along with the blockade of palmitate synthesis or global palmitoylation, augments PARP1 trapping and sensitizes high-grade ovarian cancer (HGSOC) cells to the PARPi Niraparib. Patient-derived PARP1 variants R138C and R591C display hyper-palmitoylation, impaired trapping, and PARPi resistance through an indirect mechanism independent of palmitoylation at the mutation sites. ZDHHC12 knockdown restores PARP1 trapping and resensitizes resistant cells and xenografts to Niraparib. These findings establish ZDHHC12-mediated PARP1 palmitoylation as a targetable vulnerability to overcome PARPi resistance.