title: A role for the MRN complex in ATR activation via TOPBP1 recruitment.
abstract: The MRN (MRE11-RAD50-NBS1) complex has been implicated in many aspects of the DNA damage response. It has key roles in sensing and processing DNA double-strand breaks, as well as in activation of ATM (ataxia telangiectasia mutated). We reveal a function for MRN in ATR (ATM- and RAD3-related) activation by using defined ATR-activating DNA structures in Xenopus egg extracts. Strikingly, we demonstrate that MRN is required for recruitment of TOPBP1 to an ATR-activating structure that contains a single-stranded DNA (ssDNA) and a double-stranded DNA (dsDNA) junction and that this recruitment is necessary for phosphorylation of CHK1. We also show that the 911 (RAD9-RAD1-HUS1) complex is not required for TOPBP1 recruitment but is essential for TOPBP1 function. Thus, whereas MRN is required for TOPBP1 recruitment at an ssDNA-to-dsDNA junction, 911 is required for TOPBP1 "activation." These findings provide molecular insights into how ATR is activated.
authors.affiliation: Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA.
authors.forename: Anja M
authors.initials: AM
authors.lastname: Duursma
authors.forename: Robert
authors.initials: R
authors.lastname: Driscoll
authors.forename: Josh E
authors.initials: JE
authors.lastname: Elias
authors.forename: Karlene A
authors.initials: KA
authors.lastname: Cimprich
mesh_terms: D000818:Animals; D064007:Ataxia Telangiectasia Mutated Proteins; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D000071877:Checkpoint Kinase 1; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D045643:DNA Repair Enzymes; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004789:Enzyme Activation; D006801:Humans; D000076228:MRE11 Homologue Protein; D046912:Multiprotein Complexes; D009690:Nucleic Acid Conformation; D010766:Phosphorylation; D011485:Protein Binding; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D014162:Transfection; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*; D014982:Xenopus laevis / Q000235:genetics / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; C511264:Hus1 protein, Xenopus; C510917:Mre11 protein, Xenopus; D046912:Multiprotein Complexes; C511600:NBN protein, Xenopus; C511263:Rad1 protein, Xenopus; C542167:Rad50 protein, Xenopus; C509993:TopBP1 protein, Xenopus; D025521:Tumor Suppressor Proteins; D029867:Xenopus Proteins; C069930:rad9 protein; D011494:Protein Kinases; C576898:Atr protein, Xenopus; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; C000605867:CHEK1 protein, human; D000071877:Checkpoint Kinase 1; C000605875:Chek1 protein, Xenopus; D017346:Protein Serine-Threonine Kinases; D000076228:MRE11 Homologue Protein; D045643:DNA Repair Enzymes