title: TopBP1 activates the ATR-ATRIP complex.
abstract: 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.
authors.affiliation: Division of Biology 216-76, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Akiko
authors.initials: A
authors.lastname: Kumagai
authors.forename: Joon
authors.initials: J
authors.lastname: Lee
authors.forename: Hae Yong
authors.initials: HY
authors.lastname: Yoo
authors.forename: William G
authors.initials: WG
authors.lastname: Dunphy
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D004249:DNA Damage; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D017930:Genes, Reporter; D006801:Humans; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D009865:Oocytes / Q000502:physiology; D017354:Point Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis
chemical_list: C495984:ATRIP protein, Xenopus; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D011994:Recombinant Proteins; C110513:TOPBP1 protein, human; C509993:TopBP1 protein, Xenopus; D025521:Tumor Suppressor Proteins; D029867:Xenopus Proteins; C576898:Atr protein, Xenopus; C576324:ATM protein, human; C576597:ATR protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases