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Mus81-mediated DNA cleavage resolves replication forks stalled by topoisomerase I-DNA complexes

Marie Regairaz1, Yong-Wei Zhang, Haiqing Fu

  • 1Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.

The Journal of Cell Biology
|November 30, 2011
PubMed

Insights

The endonuclease Mus81-Eme1 prevents DNA damage from topoisomerase I inhibitors by cleaving stalled replication forks. This mechanism allows cells to survive topoisomerase I inhibition and maintain replication fork progression.

Area of Science:

  • Molecular Biology
  • Genetics
  • Cancer Research

Background:

  • DNA topoisomerases relieve DNA supercoiling during replication.
  • Topoisomerase I (Top1) inhibitors, like camptothecin (CPT), trap Top1-DNA complexes, causing DNA double-strand breaks (DSBs) during replication.
  • Cells possess mechanisms to mitigate Top1 inhibitor-induced DNA damage.

Purpose of the Study:

  • To elucidate the cellular mechanism preventing Top1 inhibitor-induced replication-dependent DNA damage.
  • To investigate the role of the Mus81-Eme1 endonuclease in response to Top1 inhibition.

Main Methods:

  • Cell-based assays to assess DNA damage and cell survival.
  • Biochemical experiments to determine Mus81-Eme1 activity on Top1-DNA cleavage complexes and replication forks.
  • DNA combing to analyze replication fork dynamics.

Main Results:

  • Mus81-Eme1 is essential for generating DSBs in response to Top1 inhibition, promoting cell survival.
  • Mus81-Eme1 cleaves stalled replication forks, not Top1-DNA cleavage complexes.
  • DNA combing revealed that Mus81 activity facilitates replication fork progression after CPT treatment.

Conclusions:

  • Mus81-Eme1 acts as a structure-specific endonuclease that resolves stalled replication forks under Top1 inhibition.
  • This cleavage allows for the dissipation of supercoiling, spontaneous Top1-DNA complex reversal, and continued replication fork progression, thereby preventing lethal DNA damage.

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