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NBS1 regulates a novel apoptotic pathway through Bax activation

Kenta Iijima1, Chizuko Muranaka, Junya Kobayashi

  • 1Department of Environmental Sciences, Faculty of Science, Ibaraki University, Bunkyo 2-1-1, Mito, Ibaraki, Japan.

DNA Repair
|July 23, 2008
PubMed

Insights

NBS1 protein regulates a novel DNA damage-induced apoptosis pathway, independent of p53. This protein disrupts the Ku70-Bax complex, crucial for eliminating damaged cells and preventing cancer.

Area of Science:

  • Cellular biology
  • Molecular oncology
  • DNA damage response

Background:

  • DNA damage repair and apoptosis are vital for preventing cancer.
  • NBS1 protein is a known regulator of DNA damage repair, forming complexes with Rad50/Mre11 and activating ATM.
  • The precise role of NBS1 in apoptosis, particularly p53-independent pathways, requires further elucidation.

Purpose of the Study:

  • To investigate the role of NBS1 in DNA damage-induced apoptosis, independent of the p53 pathway.
  • To identify the specific domains and mechanisms by which NBS1 regulates apoptosis.
  • To explore NBS1's function in disrupting the Ku70-Bax complex and its implications in cancer prevention.

Main Methods:

  • Utilized NBS1-deficient cell lines and cells expressing mutant NBS1 proteins.
  • Assessed DNA damage-induced apoptosis, Bax activation, and Caspase-3 activation.
  • Investigated protein-protein interactions between NBS1, Ku70, and Bax.
  • Analyzed the role of Ku70 acetylation in the NBS1-mediated apoptotic pathway.

Main Results:

  • NBS1 deficiency significantly reduced DNA damage-induced apoptosis, irrespective of p53 status.
  • NBS1 regulates Bax and Caspase-3 activation through domains independent of FHA, Mre11-binding, or ATM interaction, with phosphorylation sites being crucial for Bax activation.
  • NBS1 induces apoptosis by disrupting the Ku70-Bax complex, a process mediated by Ku70 acetylation and NBS1's interaction with Ku70.
  • This novel pathway operates independently of E2F1 and related pro-apoptotic factors.

Conclusions:

  • NBS1 controls a novel p53-independent apoptotic pathway crucial for eliminating cells with DNA damage.
  • NBS1 disrupts the Ku70-Bax complex via Ku70 acetylation, initiating the mitochondrial apoptotic pathway.
  • NBS1 plays a dual role in cancer prevention: precise DNA repair and elimination of damaged cells, highlighting its significance beyond homologous recombination.

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