ADP-ribosyltransferase that mediates mono-ADP-ribosylation of glutamate and aspartate residues on target proteins (PubMed:18851833, PubMed:23332125, PubMed:23474714, PubMed:25043379). In contrast to PARP1 and PARP2, it is not able to mediate poly-ADP-ribosylation (PubMed:18851833). Catalyzes mono-ADP-ribosylation of GSK3B, leading to negatively regulate GSK3B kinase activity (PubMed:23332125). Involved in translesion DNA synthesis in response to DNA damage via its interaction with PCNA (PubMed:24695737). 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 (PubMed:15674325). Interacts with PARP14 (PubMed:23473667). Interacts (via-PIP box and ubiquitin-interacting motifs) with PCNA (PubMed:24695737). Shuttles between the nuclear and cytoplasmic compartment (PubMed:15674325). A subpopulation concentrates in the nucleolus during late G1/S phase (PubMed:15674325). Highly expressed in spleen and thymus (PubMed:15674325). Intermediate levels in liver, kidney, pancreas, prostate, testis, ovary, intestine, and leukocytes (PubMed:15674325). Low expression in heart, brain, placenta, lung, skeletal muscle, and colon (PubMed:15674325). The PIP-box mediates the interaction with PCNA. Stimulated through its phosphorylation by CDK2 (PubMed:16455663). Acquires CDK-dependent phosphorylation through late-G1 to S phase, and from prometaphase to cytokinesis in the nucleolar organizing regions (PubMed:16455663). Phosphorylation is suppressed in growth-arrested cells (PubMed:16455663). Auto-mono-ADP-ribosylated on glutamate and lysine residues. Belongs to the ARTD/PARP family.