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ATM/ATR Phosphorylation of CtIP on Its Conserved Sae2-like Domain Is Required for Genotoxin-Induced DNA Resection but

Foon Wu-Baer1,2, Madeline Wong1,2, Lydia Tschoe1,2

  • 1Institute for Cancer Genetics, Columbia University Irving Medical Center, New York, NY 10032, USA.

Cells
|December 9, 2023
PubMed

Insights

ATM/ATR kinase phosphorylation of CtIP-T855 is not essential for mouse development but is crucial for DNA repair. This specific phosphorylation enhances DNA resection and chromosomal stability following genotoxin exposure.

Area of Science:

  • Molecular Biology
  • DNA Repair Mechanisms
  • Cellular Stress Response

Background:

  • Homology-directed repair (HDR) of DNA double-strand breaks (DSBs) relies on DNA end resection by the Mre11/Rad50/Nbs1 complex.
  • CtIP/Sae2 protein initiates DNA resection by promoting Mre11-mediated endonuclease cleavage.
  • Conserved phosphorylation sites on CtIP/Sae2, including T843 (CDK) and T855 (ATM/ATR), are vital for DNA resection.

Purpose of the Study:

  • To investigate the functional role of ATM/ATR kinase phosphorylation at CtIP-T855 in DNA repair and animal development.
  • To analyze the consequences of mutating the CtIP-T855 phosphorylation site using a mouse model.

Main Methods:

  • Generation and analysis of mice expressing the CtIP-T855A mutant.
  • Assessment of embryonic lethality, animal development, and ionizing radiation sensitivity.
  • Evaluation of DNA resection, chromosomal stability, and HDR-mediated repair in mouse embryo fibroblasts (MEFs).

Main Results:

  • Homozygous CtIP-T855A mutant mice develop normally, unlike CtIP-null or CtIP-T843A mutant mice which are embryonically lethal.
  • CtIP-T855A mutant mice exhibit hypersensitivity to ionizing radiation.
  • MEFs from CtIP-T855A mutant mice show significant defects in DNA resection, chromosomal stability, and HDR.

Conclusions:

  • ATM/ATR phosphorylation of CtIP-T855 is dispensable for normal mouse development.
  • This phosphorylation significantly enhances CtIP-mediated DNA resection and repair efficiency under genotoxic stress conditions.
  • CtIP-T855 phosphorylation plays a critical role in maintaining genomic integrity following DNA damage.
Keywords:
ATM/ATR phosphorylationCtIPDNA break repairDNA resectionMre11genotoxic stresshomologous recombination

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