A forward chemical genetic screen reveals an inhibitor of the Mre11-Rad50-Nbs1 complex

• Published in: Nature chemical biology Vol. 4; no. 2; pp. 119 - 125
• Main Authors: Gautier, Jean, Dupré, Aude, Boyer-Chatenet, Louise, Sattler, Rose M, Modi, Ami P, Lee, Ji-Hoon, Nicolette, Matthew L, Kopelovich, Levy, Jasin, Maria, Baer, Richard, Paull, Tanya T
• Format: Journal Article
• Language: English
• Published: United States Nature Publishing Group 01.02.2008
• Subjects: Animals; Ataxia Telangiectasia - genetics; Ataxia Telangiectasia - metabolism; ATP-Binding Cassette Transporters - metabolism; Biochemistry; Cell Cycle - drug effects; Cell Extracts; Cell Line; DNA repair; DNA-Binding Proteins - metabolism; Drug Design; Humans; Inhibitor drugs; Molecular Structure; MRE11 Homologue Protein; Mutation; Protein Binding; Pyrimidinones - chemistry; Pyrimidinones - pharmacology; Signal transduction; Signal Transduction - drug effects; Thiones - chemistry; Thiones - pharmacology; Tumor Suppressor Proteins - metabolism; Xenopus laevis; Xenopus Proteins - metabolism
• ISSN: 1552-4450; 1552-4469
• DOI: 10.1038/nchembio.63

The MRN (Mre11-Rad50-Nbs1)-ATM (ataxia-telangiectasia mutated) pathway is essential for sensing and signaling from DNA double-strand breaks. The MRN complex acts as a DNA damage sensor, maintains genome stability during DNA replication, promotes homology-dependent DNA repair and activates ATM. MRN is essential for cell viability, which has limited functional studies of the complex. Small-molecule inhibitors of MRN could circumvent this experimental limitation and could also be used as cellular radio- and chemosensitization compounds. Using cell-free systems that recapitulate faithfully the MRN-ATM signaling pathway, we designed a forward chemical genetic screen to identify inhibitors of the pathway, and we isolated 6-(4-hydroxyphenyl)-2-thioxo-2,3-dihydro-4(1H)-pyrimidinone (mirin, 1) as an inhibitor of MRN. Mirin prevents MRN-dependent activation of ATM without affecting ATM protein kinase activity, and it inhibits Mre11-associated exonuclease activity. Consistent with its ability to target the MRN complex, mirin abolishes the G2/M checkpoint and homology-dependent repair in mammalian cells.