Overexpression of HDAC1 or HDAC2 decreases PARP-1-NEDD8 trimer binding. NEDP1 KO U2OS cells were transfected with GFP or GFP fused to the first two zinc finger domains of PARP-1 (GFP-Zn1+2). Cells were also co-transfected, as indicated, with empty FLAG vector, HDAC1-FLAG, or HDAC2-FLAG. 24 hours post transfection, cells were harvested and immunoprecipitation was performed on the lysates with GFP-Trap. Immunoprecipitated proteins were resolved by SDS-PAGE followed by Western blot analysis with the indicated antibodies. 