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

Nat Chem Biol. 2008 Feb;4(2):119-25. doi: 10.1038/nchembio.63. Epub 2008 Jan 6.


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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • ATP-Binding Cassette Transporters / metabolism*
  • Animals
  • Ataxia Telangiectasia / genetics
  • Ataxia Telangiectasia / metabolism
  • Cell Cycle / drug effects
  • Cell Extracts
  • Cell Line
  • DNA-Binding Proteins / metabolism*
  • Drug Design*
  • Humans
  • MRE11 Homologue Protein
  • Molecular Structure
  • Protein Binding
  • Pyrimidinones / chemistry
  • Pyrimidinones / pharmacology*
  • Signal Transduction / drug effects
  • Thiones / chemistry
  • Thiones / pharmacology*
  • Tumor Suppressor Proteins / metabolism*
  • Xenopus Proteins / metabolism*
  • Xenopus laevis


  • 6-(4-hydroxyphenyl)-2-thioxo-2,3-dihydro-4(1H)-pyrimidinone
  • ATP-Binding Cassette Transporters
  • Cell Extracts
  • DNA-Binding Proteins
  • Mre11 protein, Xenopus
  • NBN protein, Xenopus
  • Pyrimidinones
  • Thiones
  • Tumor Suppressor Proteins
  • Xenopus Proteins
  • MRE11 Homologue Protein

Associated data

  • PubChem-Substance/46391368
  • PubChem-Substance/46391369
  • PubChem-Substance/46391370
  • PubChem-Substance/46391371
  • PubChem-Substance/46391372
  • PubChem-Substance/46391373