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The MRX Complex Ensures NHEJ Fidelity through Multiple Pathways Including Xrs2-FHA-Dependent Tel1 Activation

Daichi Iwasaki1,2, Kayoko Hayashihara1, Hiroki Shima3

  • 1Department of Integrated Protein Functions, Institute for Protein Research, Osaka University, Suita, Osaka, Japan.

Plos Genetics
|March 19, 2016
PubMed

Insights

The Xrs2 FHA domain is crucial for accurate DNA double-strand break (DSB) repair by suppressing imprecise repair and promoting Tel1 kinase activation. This coordinated action maintains genomic stability.

Area of Science:

  • Molecular Biology
  • Genetics
  • Cell Biology

Background:

  • DNA double-strand breaks (DSBs) are highly cytotoxic lesions that can lead to genomic instability.
  • Precise repair of DSBs is essential for maintaining genomic integrity.
  • The Mre11-Rad50-Xrs2/Nbs1 (MRX/N) complex, including the Xrs2/Nbs1 subunit, plays a critical role in initiating DSB repair pathways.

Purpose of the Study:

  • To investigate the specific role of the Xrs2 forkhead-associated (FHA) domain in DNA double-strand break (DSB) repair fidelity.
  • To elucidate the mechanism by which the Xrs2 FHA domain contributes to the DNA damage response pathway, particularly in relation to Tel1 kinase activation.

Main Methods:

  • Utilized budding yeast as a model system.
  • Investigated the function of the Xrs2 FHA domain in DSB repair suppression and Tel1 activation.
  • Assessed the impact of Xrs2 FHA domain mutations on DSB repair outcomes and Tel1 signaling.

Main Results:

  • The Xrs2 FHA domain is essential for suppressing imprecise DSB repair.
  • The Xrs2 FHA domain promotes robust activation of Tel1 kinase in response to DNA damage.
  • This Tel1 activation role is independent of the Xrs2 C-terminus-mediated Tel1 recruitment.
  • Both the Xrs2 FHA domain and Tel1 kinase are required for efficient Ku complex removal from DSB ends, reducing imprecise end-joining.

Conclusions:

  • The Xrs2 FHA domain is a key regulator of DSB repair fidelity.
  • The Xrs2 FHA domain and Tel1 kinase function cooperatively to ensure accurate repair of DNA double-strand breaks.
  • This coordinated mechanism is vital for maintaining genomic stability.

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