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A conserved Ctp1/CtIP C-terminal peptide stimulates Mre11 endonuclease activity

Aleksandar Zdravković1,2, James M Daley3, Arijit Dutta3

  • 1School and Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Kanagawa 226-8503, Japan.

Proceedings of the National Academy of Sciences of the United States of America
|April 10, 2021
PubMed

Insights

The Mre11-Rad50-Nbs1 (MRN) complex repairs DNA double-strand breaks. Ctp1 phosphorylation activates MRN

Area of Science:

  • Molecular Biology
  • DNA Repair Mechanisms
  • Protein-Protein Interactions

Background:

  • The Mre11-Rad50-Nbs1 (MRN) complex is crucial for DNA double-strand break (DSB) repair via homologous recombination (HR).
  • MRN's endonuclease activity is essential for processing DSB ends to initiate HR.
  • Ctp1, the fission yeast homolog of human CtIP, stimulates MRN endonuclease activity.

Purpose of the Study:

  • To elucidate the mechanism by which Ctp1 stimulates MRN endonuclease activity.
  • To identify the specific domains of Ctp1 involved in MRN activation.
  • To determine if this mechanism is conserved across species.

Main Methods:

  • Purification of interacting proteins.
  • In vitro biochemical assays to measure endonuclease activity.
  • Site-directed mutagenesis to identify functional domains.

Main Results:

  • Ctp1 phosphorylation promotes MRN endonuclease activity by enhancing Ctp1-Nbs1 association.
  • The conserved C-terminal 15 amino acids of Ctp1 (CT15) are indispensable and sufficient for MRN activation.
  • The human CtIP CT15 equivalent also stimulates human MRE11 activity, indicating functional conservation.

Conclusions:

  • Nbs1-mediated recruitment of the Ctp1 C-terminus is a key mechanism for activating Mre11 endonuclease activity.
  • This finding highlights a conserved pathway for regulating DNA repair.
  • The study provides insights into the regulation of DNA double-strand break repair.
Keywords:
Ctp1/CtIPMre11-Rad50-Nbs1double-strand break repairfission yeasthomologous recombination

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