Inhibiting ADP-ribosyl transferases with PARP-inhibitors is considered a promising strategy for the treatment of many cancers and ischemia, but most of the cellular targets are poorly characterized. Here, we describe an inhibitor of ADP-ribosyltransferase-3/poly(ADP-ribose) polymerase-3 (ARTD3), a regulator of DNA repair and mitotic progression. In vitro profiling against 12 members of the enzyme family suggests selectivity for ARTD3, and crystal structures illustrate the molecular basis for inhibitor selectivity. The compound is active in cells, where it elicits ARTD3-specific effects at submicromolar concentration. Our results show that by targeting the nicotinamide binding site, selective inhibition can be achieved among the closest relatives of the validated clinical target, ADP-ribosyltransferase-1/poly(ADP-ribose) polymerase-1.

Adenovirus infections are widespread in society and are occasionally associated with severe, but rarely with life-threatening, disease in otherwise healthy individuals. In contrast, adenovirus infections present a real threat to immunocompromised individuals and can result in disseminated and fatal disease. The number of patients undergoing immunosuppressive therapy for solid organ or hematopoietic stem cell transplantation is steadily increasing, as is the number of AIDS patients, and this makes the problem of adenovirus infections even more urgent to solve. There is no formally approved treatment of adenovirus infections today, and existing antiviral agents evaluated for their antiadenoviral effect give inconsistent results. We have developed a whole cell-based assay for high-throughput screening of potential antiadenoviral compounds. The assay is unique in that it is based on a replication-competent adenovirus type 11p green fluorescent protein (GFP)-expressing vector (RCAd11pGFP). This allows measurement of fluorescence changes as a direct result of RCAd11pGFP genome expression. Using this assay, we have screened 9,800 commercially available small organic compounds. Initially, we observed approximately 400 compounds that inhibited adenovirus expression in vitro by >80%, but only 24 were later confirmed as dose-dependent inhibitors of adenovirus. One compound in particular, 2-{[2-(benzoylamino)benzoyl]amino}-benzoic acid, turned out to be a potent inhibitor of adenovirus replication.

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The diphtheria toxin-like ADP-ribosyltransferases (ARTDs) are an enzyme family that catalyzes the transfer of ADP-ribose units onto substrate proteins by using nicotinamide adenine dinucleotide (NAD(+)) as a cosubstrate. They have a documented role in chromatin remodelling and DNA repair, and inhibitors of ARTD1 and 2 (PARP1 and 2) are currently in clinical trials for the treatment of cancer. The detailed function of most other ARTDs is still unknown. By using virtual screening, we identified small ligands of ARTD7 (PARP15/BAL3) and ARTD8 (PARP14/BAL2). Thermal-shift assays confirmed that 16 compounds, belonging to eight structural classes, bound to ARTD7/ARTD8. Affinity measurements with isothermal titration calorimetry for two isomers of the most promising hit compound confirmed binding in the low micromolar range to ARTD8. Crystal structures showed anchoring of the hits in the nicotinamide pocket. These results form a starting point in the development of chemical tools for the study of the role and function of ARTD7 and ARTD8.

Protein ADP-ribosylation is a post-translational modification involved in DNA repair, protein degradation, transcription regulation, and epigenetic events. Intracellular ADP-ribosylation is catalyzed predominantly by ADP-ribosyltransferases with diphtheria toxin homology (ARTDs). The most prominent member of the ARTD family, poly(ADP-ribose) polymerase-1 (ARTD1/PARP1) has been a target for cancer drug development for decades. Current PARP inhibitors are generally non-selective, and inhibit the mono-ADP-ribosyltransferases with low potency. Here we describe the synthesis of acylated amino benzamides and screening against the mono-ADP-ribosyltransferases ARTD7/PARP15, ARTD8/PARP14, ARTD10/PARP10, and the poly-ADP-ribosyltransferase ARTD1/PARP1. The most potent compound inhibits ARTD10 with sub-micromolar IC50.