title: Discovery of novel poly(ADP-ribose) glycohydrolase inhibitors by a quantitative assay system using dot-blot with anti-poly(ADP-ribose).
abstract: Poly(ADP-ribosyl)ation, which is mainly regulated by poly(ADP-ribose) polymerase (PARP) and poly(ADP-ribose) glycohydrolase (PARG), is a unique protein modification involved in cellular responses such as DNA repair and replication. PARG hydrolyzes glycosidic linkages of poly(ADP-ribose) synthesized by PARP and liberates ADP-ribose residues. Recent studies have suggested that inhibitors of PARG are able to be potent anti-cancer drug. In order to discover the potent and specific Inhibitors of PARG, a quantitative and high-throughput screening assay system is required. However, previous PARG assay systems are not appropriate for high-throughput screening because PARG activity is measured by radioactivities of ADP-ribose residues released from radioisotope (RI)-labeled poly(ADP-ribose). In this study, we developed a non-RI and quantitative assay system for PARG activity based on dot-blot assay using anti-poly(ADP-ribose) and nitrocellulose membrane. By our method, the maximum velocity (Vmax) and the michaelis constant (km) of PARG reaction were 4.46 microM and 128.33 micromol/min/mg, respectively. Furthermore, the IC50 of adenosine diphosphate (hydroxymethyl) pyrrolidinediol (ADP-HPD), known as a non-competitive PARG inhibitor, was 0.66 microM. These kinetics values were similar to those obtained by traditional PARG assays. By using our assay system, we discovered two novel PARG inhibitors that have xanthene scaffold. Thus, our quantitative and convenient method is useful for a high-throughput screening of PARG specific inhibitors.
authors.affiliation: Genome and Drug Research Center, Tokyo University of Science, Japan. nokita7@rs.noda.tus.ac.jp
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Okita
authors.forename: Daisuke
authors.initials: D
authors.lastname: Ashizawa
authors.forename: Ryo
authors.initials: R
authors.lastname: Ohta
authors.forename: Hideaki
authors.initials: H
authors.lastname: Abe
authors.forename: Sei-ichi
authors.initials: S
authors.lastname: Tanuma
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D002417:Cattle; D055808:Drug Discovery; D004354:Drug Screening Assays, Antitumor; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D006026:Glycoside Hydrolases / Q000037:antagonists & inhibitors*; D006801:Humans; D020128:Inhibitory Concentration 50; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D011994:Recombinant Proteins; D006026:Glycoside Hydrolases; C022407:poly ADP-ribose glycohydrolase