NEDD8 trimers bind to GFP-PARP-1. WT or NEDP1 U2OS KO cells were transfected with GFP or with full-length GFP-PARP-1 and 24 hours later treated as indicated with H2O2 (600 μM) for 30 min before cell lysates were collected. Immunoprecipitation was then performed with GFP-Trap, and bound proteins were resolved by SDS-PAGE and processed for Western blot analysis with the indicated antibodies. GFP-PARP-1 but not GFP alone can co-immunoprecipitate NEDD8 trimers from WT cells only after H2O2 treatment or from both treated or untreated NEDP1 KO cells. 