TopBP1 activates the ATR-ATRIP complex

Cell. 2006 Mar 10;124(5):943-55. doi: 10.1016/j.cell.2005.12.041.


ATR is a key regulator of checkpoint responses to incompletely replicated and damaged DNA, but the mechanisms underlying control of its kinase activity are unknown. TopBP1, the vertebrate homolog of yeast Cut5/Dbp11, has dual roles in initiation of DNA replication and regulation of checkpoint responses. We show that recombinant TopBP1 induces a large increase in the kinase activity of both Xenopus and human ATR. The ATR-activating domain resides in a conserved segment of TopBP1 that is distinct from its numerous BRCT repeats. The isolated ATR-activating domain from TopBP1 induces ectopic activation of ATR-dependent signaling in both Xenopus egg extracts and human cells. Furthermore, Xenopus egg extracts containing a version of TopBP1 with an inactivating point mutation in the ATR-activating domain are defective in checkpoint regulation. These studies establish that activation of ATR by TopBP1 is a crucial step in the initiation of ATR-dependent signaling processes.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Ataxia Telangiectasia Mutated Proteins
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Cycle / physiology*
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • DNA Damage
  • DNA Repair
  • DNA-Binding Proteins / metabolism
  • Enzyme Activation
  • Genes, Reporter
  • Humans
  • Macromolecular Substances
  • Molecular Sequence Data
  • Nuclear Proteins
  • Oocytes / physiology
  • Point Mutation
  • Protein Structure, Tertiary
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Alignment
  • Signal Transduction / physiology
  • Tumor Suppressor Proteins / metabolism
  • Xenopus Proteins / genetics
  • Xenopus Proteins / metabolism*
  • Xenopus laevis


  • ATRIP protein, Xenopus
  • Carrier Proteins
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • Macromolecular Substances
  • Nuclear Proteins
  • Recombinant Proteins
  • TOPBP1 protein, human
  • TopBP1 protein, Xenopus
  • Tumor Suppressor Proteins
  • Xenopus Proteins
  • Atr protein, Xenopus
  • ATM protein, human
  • ATR protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • Protein-Serine-Threonine Kinases