ADP-ribosyltransferase which, in association with E3 ligase DTX3L, plays a role in DNA damage repair and in immune responses including interferon-mediated antiviral defenses (PubMed:27796300). Within the complex, enhances DTX3L E3 ligase activity which is further enhanced by PARP9 binding to poly(ADP-ribose) (By similarity). In addition, positively regulates DTXL3 protein levels (By similarity). In association with DTX3L and in presence of E1 and E2 enzymes, mediates NAD(+)-dependent mono-ADP-ribosylation of ubiquitin which prevents ubiquitin conjugation to substrates such as histones (By similarity). During DNA repair, PARP1 recruits PARP9/BAL1-DTX3L complex to DNA damage sites via PARP9 binding to ribosylated PARP1 (By similarity). Subsequent PARP1-dependent PARP9/BAL1-DTX3L-mediated ubiquitination promotes the rapid and specific recruitment of 53BP1/TP53BP1, UIMC1/RAP80, and BRCA1 to DNA damage sites (By similarity). In response to DNA damage, PARP9-DTX3L complex is required for efficient non-homologous end joining (NHEJ) but the complex function is restrained by PARP9 activity (By similarity). Dispensable for B-cell receptor (BCR) assembly through V(D)J recombination and class switch recombination (CSR) (PubMed:28105679). In macrophages, positively regulates pro-inflammatory cytokines production in response to IFNG stimulation by suppressing PARP14-mediated STAT1 ADP-ribosylation and thus promoting STAT1 phosphorylation (PubMed:27796300). Also suppresses PARP14-mediated STAT6 ADP-ribosylation (By similarity). [protein]-C-terminal glycine + NAD(+) = [protein]-C-terminal O-(ADP-D-ribosyl)-glycine + nicotinamide Binding to poly(ADP-ribose) does not affect its activity. Forms a stable complex with E3 ligase DTX3L; the interaction is required for PARP9 mediated ADP-ribosylation of ubiquitin. Interacts (via PARP catalytic domain) with DTX3L (via N-terminus). Forms a complex with STAT1 and DTX3L independently of IFNB1 or IFNG-mediated STAT1 'Tyr-701' phosphorylation. Forms a complex with STAT1, DTX3L and histone H2B H2BC9/H2BJ; the interaction is likely to induce H2BC9/H2BJ ubiquitination. Interacts (via N-terminus) with STAT1. Interacts with PARP14 in IFNG-stimulated macrophages; the interaction prevents PARP14-mediated STAT1 and STAT6 ADP-riboslylation. Interacts with PARP1 (when poly-ADP-ribosylated). Shuttles between the nucleus and the cytosol. Translocates to the nucleus in response to IFNG or IFNB1 stimulation. Export to the cytosol depends on the interaction with DTX3L. Localizes at sites of DNA damage in a PARP1-dependent manner. Highly expressed in the thymus and intestine (PubMed:18069692). Expressed in macrophages (PubMed:27796300). Developmentally regulated. Expressed prominently in the developing thymus and the gut, and also weakly expressed in specific regions of the developing brain. Up-regulated by IFNG in macrophages. Down-regulated by IL4 in macrophages. Macro domains 1 and 2 may be involved in the binding to poly(ADP-ribose). Macro domain 2 is required for recruitment to DNA damage sites. Macro domains 1 and 2 are probably dispensable for the interaction with STAT1 and DTX3L and for STAT1 phosphorylation. ADP-ribosylated by PARP14. No visible phenotype. Mice are viable, fertile and are born at the expected Mendelian rate with a slight decrease in male frequency. No defect in B-cell development, maturation and maintenance in periphery. Slight decrease in the number of follicular B-cell associated with an increase in the number of marginal zone B-cells. Belongs to the ARTD/PARP family.