Site-specific characterization of the Asp- and Glu-ADP-ribosylated proteome

A proteomic method to identify human proteins post-translationally modified by poly(ADP-ribosyl)ation is reported, which will help yield further insights into the biological role of this modification. Poly(ADP-ribosyl)ation is catalyzed by a family of enzymes known as PARPs. We describe a method to characterize the human aspartic acid– and glutamic acid–ADP-ribosylated proteome. We identified 1,048 ADP-ribosylation sites on 340 proteins involved in a wide array of nuclear functions; among these were many previously unknown PARP downstream targets whose ADP-ribosylation was sensitive to PARP inhibitor treatment. We also confirmed that iniparib had a negligible effect on PARP activity in intact cells.