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TDP1-independent pathways in the process and repair of TOP1-induced DNA damage

Huimin Zhang1, Yun Xiong1, Dan Su1

  • 1Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.

Nature Communications
|July 22, 2022
PubMed

Insights

Anticancer drugs create DNA damage by trapping topoisomerase I (TOP1). Our study reveals MUS81 mediates double-strand breaks (DSBs) in TDP1-deficient cells, suggesting alternative DNA repair pathways for TOP1-induced damage.

Area of Science:

  • Molecular Biology
  • Genetics
  • Cancer Research

Background:

  • Anticancer drugs like camptothecin (CPT) induce DNA damage by forming topoisomerase I-cleavage complexes (TOP1cc).
  • The precise mechanisms and alternative pathways involved in repairing TOP1cc, particularly in conjunction with TDP1, remain incompletely understood.
  • TDP1 is a crucial enzyme for resolving TOP1cc by cleaving the bond between TOP1 and the 3'-DNA end.

Purpose of the Study:

  • To elucidate the roles of alternative DNA repair pathways in the context of TOP1cc.
  • To investigate the relationship between TDP1 and other DNA repair factors, including MUS81 and APEX1/2, in managing TOP1-induced DNA damage.
  • To identify key mediators of double-strand break (DSB) formation in TDP1-deficient cells.

Main Methods:

  • Unbiased whole-genome CRISPR screening was employed to identify genetic factors influencing TOP1cc repair.
  • Generation of cell lines co-deficient in TDP1 and other relevant DNA repair genes.
  • Assessment of double-strand break (DSB) formation in various genetic backgrounds.

Main Results:

  • MUS81 was identified as a significant factor mediating the generation of excess DSBs in TDP1 knockout (KO) cells.
  • APEX1/2 were found to be synthetically lethal with TDP1.
  • Deficiency in APEX1/2 did not decrease DSB formation in TDP1 KO cells, indicating a distinct role from MUS81 in DSB generation.

Conclusions:

  • TOP1cc can be resolved either directly by TDP1 or converted into DSBs.
  • The Homologous Recombination (HR) pathway plays a role in repairing DSBs generated from TOP1cc.
  • MUS81 is implicated in the pathway that converts TOP1cc into DSBs when TDP1 is absent.

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