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Ataxia telangiectasia-mutated (ATM) kinase activity is regulated by ATP-driven conformational changes in the

Ji-Hoon Lee1, Michael R Mand, Rajashree A Deshpande

  • 1Howard Hughes Medical Institute and the Department of Molecular Genetics and Microbiology, The University of Texas at Austin, Austin, Texas 78712, USA.

The Journal of Biological Chemistry
|March 26, 2013
PubMed

Insights

The Mre11/Rad50/Nbs1 (MRN) complex activates ATM kinase at DNA break sites. ATP binding by Rad50, not hydrolysis, is crucial for MRN to stimulate ATM, with the ATP-bound MRN form being key.

Area of Science:

  • DNA damage response
  • Protein kinase activation
  • Molecular mechanisms of DNA repair

Background:

  • The Ataxia Telangiectasia-Mutated (ATM) kinase is vital for DNA double-strand break repair.
  • ATM is recruited and activated by the Mre11/Rad50/Nbs1 (MRN) complex.
  • MRN complex conformational states are regulated by Rad50's ATP binding and hydrolysis.

Purpose of the Study:

  • To elucidate the specific roles of Rad50's ATP binding and hydrolysis in MRN-mediated ATM activation.
  • To investigate the contribution of Mre11 nuclease activity and Rad50 structural domains to ATM activation.
  • To define the critical MRN complex conformation required for ATM activation.

Main Methods:

  • Utilized an ATP analog-sensitive form of ATM to probe functional requirements.
  • Assessed the impact of mutations in Mre11 and Rad50 domains on ATM activation.
  • Investigated the role of mirin compound in inhibiting MRN-mediated ATM activation.

Main Results:

  • Rad50's ATP binding, not hydrolysis, is essential for MRN to stimulate ATM.
  • Mre11 nuclease activity is dispensable for ATM activation, though certain catalytic domain mutations impair it.
  • Rad50 coiled-coil domains are crucial for MRN DNA binding and ATM activation; the zinc hook's role in tethering Rad50 monomers is critical for Nbs1 binding and ATP binding.

Conclusions:

  • The ATP-bound conformation of the MRN complex is the essential form for stimulating ATM kinase activity.
  • Rad50's ATP binding and structural integrity, particularly the zinc hook, are critical for MRN function in DNA repair signaling.
Keywords:
DNA RepairPhosphorylationPhosphorylation EnzymesProtein ConformationProtein DNA-Interaction

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