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Updated: Aug 3, 2025

Analysis of DNA Double-strand Break DSB Repair in Mammalian Cells
13:10

Analysis of DNA Double-strand Break DSB Repair in Mammalian Cells

Published on: September 8, 2010

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The APE2 nuclease is essential for DNA double-strand break repair by microhomology-mediated end joining

Hubert Fleury1, Myles K MacEachern1, Clara M Stiefel2

  • 1Department of Molecular, Cellular & Developmental Biology, University of Colorado Boulder, Boulder, CO, USA.

Molecular Cell
|April 12, 2023
PubMed

Insights

The APE2 nuclease is crucial for microhomology-mediated end joining (MMEJ) DNA repair in cancer cells. Targeting APE2 could offer a new strategy for treating homologous recombination-deficient cancers.

Area of Science:

  • Molecular Biology
  • Cancer Research
  • Genetics

Background:

  • Microhomology-mediated end joining (MMEJ) is a DNA double-strand break (DSB) repair pathway.
  • MMEJ is essential for the proliferation of homologous recombination-deficient (HRD) tumors.
  • Targeting MMEJ is a promising strategy for eliminating HRD cancers, but requires a deeper understanding of the pathway.

Purpose of the Study:

  • To identify novel factors involved in MMEJ repair.
  • To elucidate the mechanism by which APE2 functions in MMEJ.
  • To explore the therapeutic potential of targeting APE2 in HRD cancers.

Main Methods:

  • Investigated the role of APE2 nuclease in MMEJ using cellular assays.
  • Assessed MMEJ inhibition in cells lacking APE2 at telomeres and chromosomal breaks.
  • Determined the epistatic relationship between APE2 and Pol Theta in MMEJ.
  • Characterized APE2's flap-cleaving activity and its dependence on nuclease activity for MMEJ.
  • Identified a novel domain in APE2 required for its recruitment to DSBs.

Main Results:

  • APE2 nuclease was identified as a key effector of MMEJ.
  • Loss of APE2 significantly inhibited MMEJ at deprotected telomeres and intra-chromosomal DSBs.
  • APE2 function in MMEJ was found to be epistatic with Pol Theta.
  • APE2 exhibits intrinsic flap-cleaving activity essential for its MMEJ role.
  • A previously uncharacterized domain of APE2 is required for its recruitment to DSBs.

Conclusions:

  • APE2 plays a critical, previously unrecognized role in MMEJ.
  • HRD cells are dependent on APE2 for MMEJ repair.
  • APE2's function in MMEJ presents a potential therapeutic vulnerability in HRD cancers.
Keywords:
APE2APEX2DNA repairHR-deficientHomologous RecombinationMMEJPARPcancersynthetic lethality

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