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The Mre11/Rad50/Nbs1 complex and its role as a DNA double-strand break sensor for ATM

Tanya T Paull1, Ji-Hoon Lee

  • 1Department of Molecular Genetics and Microbiology, Institute of Cellular and Molecular Biology, University of Texas, Austin, Texas 78712, USA. tpaull@iamb.utexas.edu

Cell Cycle (Georgetown, Tex.)
|May 24, 2005
PubMed

Insights

The Mre11-Rad50-Nbs1 complex (MRN) activates ATM kinase signaling following DNA double-strand breaks (DSBs). MRN recruits ATM to DNA, enhancing its activity through protein interactions and DNA unwinding.

Area of Science:

  • Molecular biology
  • Cellular signaling
  • DNA repair mechanisms

Background:

  • DNA double-strand breaks (DSBs) trigger critical cellular responses.
  • The ATM protein kinase is central to DNA damage signaling.
  • The Mre11-Rad50-Nbs1 (MRN) complex is implicated in ATM activation.

Purpose of the Study:

  • To investigate the role of the MRN complex in ATM activation by DSBs.
  • To elucidate the mechanisms by which MRN stimulates ATM kinase activity.
  • To characterize the properties of dimeric ATM and its activation requirements.

Main Methods:

  • In vitro biochemical assays to study MRN-ATM interactions.
  • Isolation and characterization of dimeric ATM forms.
  • Analysis of DNA binding and unwinding by the MRN complex.

Main Results:

  • MRN complex stimulates ATM activity through multiple protein-protein contacts.
  • MRN enhances ATM's substrate binding affinity.
  • Dimeric ATM requires both MRN and DNA for activation, mirroring in vivo conditions.
  • MRN facilitates ATM recruitment to DNA and DNA unwinding.

Conclusions:

  • MRN is essential for ATM activation at DSBs.
  • MRN acts as a scaffold, recruiting ATM to DNA damage sites.
  • DNA unwinding by MRN is crucial for ATM activation.
  • Autophosphorylation plays a role in ATM activation by MRN and DNA.

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