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NBS1 directly activates ATR independently of MRE11 and TOPBP1

Masahiko Kobayashi1, Naoyuki Hayashi, Minoru Takata

  • 1Department of Molecular Pathology, Cancer Research Institute, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan. mkoba@staff.kanazawa-u.ac.jp

Genes to Cells : Devoted to Molecular & Cellular Mechanisms
|February 2, 2013
PubMed

Insights

NBS1 protein is crucial for ATM activation after DNA damage. This study reveals NBS1 can independently activate ATR, a key DNA repair kinase, separate from its known roles.

Area of Science:

  • Molecular Biology
  • DNA Damage Response
  • Cellular Signaling

Background:

  • NBS1 (Nibrin) is essential for activating ATM kinase in response to DNA double-strand breaks.
  • The precise mechanisms of NBS1 in DNA damage response pathways, particularly ATR activation, are not fully elucidated.

Purpose of the Study:

  • To investigate the MRE11-independent role of NBS1 in ATR activation.
  • To determine if NBS1 can directly activate ATR kinase activity.

Main Methods:

  • Utilized Nbs1 knockout and conditional Mre11 knockout DT40 cell lines.
  • Performed in vitro ATR kinase assays.
  • Conducted in vivo experiments using fusion proteins expressed in knockout cells.

Main Results:

  • NBS1's role in ATR activation is independent of MRE11, as evidenced by abrogated CHK1 phosphorylation and FANCD2 ubiquitination in Nbs1 knockout cells.
  • The N-terminal region of NBS1 directly interacts with and activates ATR kinase in vitro, independently of TOPBP1.
  • In vivo, NBS1's N-terminal region can induce ATR activation in Rad17 knockout cells, and TOPBP1's activation domain can activate ATR in Nbs1 knockout cells.

Conclusions:

  • NBS1 possesses an MRE11-independent function in activating ATR.
  • NBS1 and TOPBP1 can independently activate ATR, but both are required for full in vivo ATR activation.

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