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ATM activation and its recruitment to damaged DNA require binding to the C terminus of Nbs1

Zhongsheng You1, Charly Chahwan, Julie Bailis

  • 1Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.

Molecular and Cellular Biology
|June 21, 2005
PubMed

Insights

The DNA damage response protein ATM is activated by the MRN complex through a specific interaction between ATM

Area of Science:

  • Molecular Biology
  • Cellular Biology
  • Biochemistry

Background:

  • ATM (Ataxia-Telangiectasia Mutated) is crucial for DNA damage response.
  • ATM and other PIKKs possess amino-terminal HEAT repeat domains with unclear functions.
  • The Mre11-Rad50-Nbs1 (MRN) complex regulates ATM activation, but the precise mechanism is unknown.

Purpose of the Study:

  • To elucidate the functional relationship between the MRN complex and ATM in DNA damage response.
  • To investigate the role of HEAT repeat domains in ATM activation.
  • To identify the specific interaction mediating ATM recruitment and activation at DNA damage sites.

Main Methods:

  • Investigated interactions between fission yeast ATM (Tel1) HEAT repeats and Nbs1 C-terminal FXF/Y motifs.
  • Utilized Xenopus egg extracts to study Nbs1's role in recruiting and activating ATM at damaged DNA.
  • Assessed ATM activation in Nbs1-depleted extracts using a functional Nbs1 C-terminal fragment.

Main Results:

  • Identified specific HEAT repeats in Tel1 (ATM) that bind to the C-terminal FXF/Y motif of Nbs1.
  • Demonstrated that Nbs1 C-terminus recruits ATM to damaged DNA, leading to its autophosphorylation and activation.
  • Showed that a minimal Nbs1 fragment containing Mre11- and ATM-binding domains restores ATM activation in depleted extracts.

Conclusions:

  • The interaction between ATM HEAT repeats and the Nbs1 C-terminal FXF/Y domain is essential for ATM activation.
  • Conformational changes in the MRN complex upon DNA binding are transmitted via the FXF/Y-HEAT interface to activate ATM.
  • This interaction anchors active ATM at DNA damage sites, facilitating sustained DNA repair signaling.

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