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Topoisomerase II poisons inhibit vertebrate DNA replication through distinct mechanisms

Sabrina X Van Ravenstein1, Kavi P Mehta1, Tamar Kavlashvili1

  • 1Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, TN, USA.

The EMBO Journal
|May 17, 2022
PubMed

Insights

Topoisomerase II (TOP2) poisons like etoposide and doxorubicin inhibit DNA replication via distinct mechanisms. Etoposide causes TOP2-dependent DNA breaks and stalling, while doxorubicin causes independent stalling, yet both are TOP2-dependent for cytotoxicity.

Area of Science:

  • Molecular Biology
  • Genetics
  • Pharmacology

Background:

  • Topoisomerase II (TOP2) is crucial for unlinking chromosomes during DNA replication in vertebrates.
  • TOP2 poisons are chemotherapeutics that stabilize TOP2-DNA complexes, causing DNA breaks and cytotoxicity.
  • The precise impact of TOP2 poisons on DNA replication remains incompletely understood.

Purpose of the Study:

  • To elucidate the distinct mechanisms by which etoposide and doxorubicin inhibit DNA replication.
  • To investigate the role of TOP2 in the DNA replication inhibitory effects of these chemotherapeutics.
  • To understand the shared and distinct pathways leading to cytotoxicity.

Main Methods:

  • Utilized Xenopus egg extracts to study DNA replication dynamics.
  • Employed etoposide and doxorubicin as model TOP2 poisons.
  • Analyzed replication fork stalling and DNA break formation in vitro and in human cells.

Main Results:

  • Etoposide induces TOP2-dependent DNA breaks and stalls replication forks by trapping TOP2 behind them.
  • Doxorubicin intercalates into DNA, stalling replication forks independently of TOP2 and without significant break formation.
  • Both drugs demonstrate TOP2-dependent cytotoxicity in human cells, despite differing replication inhibition mechanisms.

Conclusions:

  • Etoposide and doxorubicin inhibit DNA replication through separate pathways.
  • Replication fork stalling mechanisms differ between etoposide and doxorubicin.
  • Despite distinct modes of action on replication, both drugs rely on TOP2 for their cytotoxic effects.
Keywords:
DNA DamageDNA replicationcancerchemotherapytopoisomerase

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