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Structurally distinct Mre11 domains mediate MRX functions in resection, end-tethering and DNA damage resistance

Corinne Cassani1, Elisa Gobbini1, Jacopo Vertemara1

  • 1Dipartimento di Biotecnologie e Bioscienze, Università di Milano-Bicocca, Milano, Italy.

Nucleic Acids Research
|February 9, 2018
PubMed

Insights

Mutations in the Mre11 protein suppress defects in DNA double-strand break repair caused by Sae2 loss. These Mre11 mutations impact DNA damage resistance by altering protein interactions at break sites.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • Sae2 protein collaborates with the Mre11-Rad50-Xrs2 (MRX) complex for DNA double-strand break (DSB) repair.
  • The precise contribution of MRX-Sae2 functions to DNA damage resistance remains unclear.

Purpose of the Study:

  • To investigate how specific mutations in the Mre11 gene can restore resistance to genotoxic agents in cells lacking Sae2.
  • To elucidate the molecular mechanisms by which these Mre11 mutations confer DNA damage resistance.

Main Methods:

  • Genetic screening for mre11 alleles that suppress sae2Δ hypersensitivity to camptothecin and phleomycin.
  • Cellular and structural analysis of mutant mre11 alleles.
  • Assessment of protein associations (MRX, Tel1, Rad9) at DSBs.
  • Evaluation of DNA resection activities (Sgs1-Dna2).

Main Results:

  • Mre11 N-terminus mutations restored resistance to both camptothecin and phleomycin by reducing MRX and Tel1 association with DSBs, thereby enhancing Sgs1-Dna2 resection.
  • Mre11 C-terminus mutations restored resistance only to phleomycin, bypassing Sae2's end-tethering role possibly by destabilizing the Mre11-Rad50 complex.
  • These findings reveal distinct roles for Mre11 domains in DNA damage response pathways.

Conclusions:

  • Structurally distinct domains of Mre11 mediate different processes crucial for resistance to genotoxic agents.
  • Understanding these domain functions provides insight into the complex mechanisms of DNA double-strand break repair.

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