A role for the MRN complex in ATR activation via TOPBP1 recruitment

Mol Cell. 2013 Apr 11;50(1):116-22. doi: 10.1016/j.molcel.2013.03.006.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Ataxia Telangiectasia Mutated Proteins
  • Binding Sites
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Line, Tumor
  • Checkpoint Kinase 1
  • Chromosomal Proteins, Non-Histone / metabolism
  • DNA Repair Enzymes
  • DNA, Single-Stranded / chemistry
  • DNA, Single-Stranded / metabolism
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Enzyme Activation
  • Humans
  • MRE11 Homologue Protein
  • Multiprotein Complexes
  • Nucleic Acid Conformation
  • Phosphorylation
  • Protein Binding
  • Protein Kinases / metabolism
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • RNA Interference
  • Transfection
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism*
  • Xenopus Proteins / genetics
  • Xenopus Proteins / metabolism*
  • Xenopus laevis / genetics
  • Xenopus laevis / metabolism*

Substances

  • Carrier Proteins
  • Cell Cycle Proteins
  • Chromosomal Proteins, Non-Histone
  • DNA, Single-Stranded
  • DNA-Binding Proteins
  • Hus1 protein, Xenopus
  • Mre11 protein, Xenopus
  • Multiprotein Complexes
  • NBN protein, Xenopus
  • Rad1 protein, Xenopus
  • Rad50 protein, Xenopus
  • TopBP1 protein, Xenopus
  • Tumor Suppressor Proteins
  • Xenopus Proteins
  • rad9 protein
  • Protein Kinases
  • Atr protein, Xenopus
  • ATM protein, human
  • Ataxia Telangiectasia Mutated Proteins
  • CHEK1 protein, human
  • Checkpoint Kinase 1
  • Chek1 protein, Xenopus
  • Protein-Serine-Threonine Kinases
  • MRE11 Homologue Protein
  • DNA Repair Enzymes