ADP-ribosyltransferase that mediates mono-ADP-ribosylation of glutamate and aspartate residues on target proteins. In contrast to PARP1 and PARP2, it is not able to mediate poly-ADP-ribosylation. Catalyzes mono-ADP-ribosylation of GSK3B, leading to negatively regulate GSK3B kinase activity. Involved in translesion DNA synthesis in response to DNA damage via its interaction with PCNA. L-lysyl-[protein] + NAD(+) = H(+) + N(6)-(ADP-D-ribosyl)-L-lysyl-[protein] + nicotinamide L-aspartyl-[protein] + NAD(+) = 4-O-(ADP-D-ribosyl)-L-aspartyl-[protein] + nicotinamide L-glutamyl-[protein] + NAD(+) = 5-O-(ADP-D-ribosyl)-L-glutamyl-[protein] + nicotinamide Interacts with MYC. Interacts with PARP14. Interacts (via-PIP box and ubiquitin-interacting motifs) with PCNA. Localizes in the cytoplasm at steady state, but shuttles between nucleus and cytoplasm in a XPO1-dependent manner. The PIP-box mediates the interaction with PCNA. Stimulated through its phosphorylation by CDK2. Acquires CDK-dependent phosphorylation through late-G1 to S phase, and from prometaphase to cytokinesis in the nucleolar organizing regions. Phosphorylation is suppressed in growth-arrested cells. Auto-mono-ADP-ribosylated on glutamate and lysine residues. Belongs to the ARTD/PARP family. Extended N-terminus.