Etoposide promotes DNA loop trapping and barrier formation by topoisomerase II

Area of Science:

• Biochemistry
• Molecular Biology
• Pharmacology

Background:

• Etoposide is a key chemotherapeutic agent and topoisomerase II poison.
• It stabilizes DNA-enzyme complexes, causing DNA breaks and cell death.
• The precise mechanism by which etoposide affects topoisomerase II dynamics remains unclear.

Purpose of the Study:

• To investigate the action of etoposide on yeast and human topoisomerase II enzymes.
• To elucidate how etoposide perturbs topoisomerase II dynamics at the single-molecule level.

Main Methods:

• Utilized sensitive single-molecule detection methods.
• Examined etoposide's effects on yeast topoisomerase II, human topoisomerase IIα, and human topoisomerase IIβ.

Main Results:

• Etoposide induces topoisomerase II to trap DNA loops, compacting DNA and altering topology.
• Loop trapping occurs post-ATP hydrolysis and pre-strand ejection.
• Etoposide decreases dimer stability but enhances the enzyme's roadblock capacity.
• Enzymes showed similar resistance to dimer separation but varied in DNA compaction and supercoil relaxation.

Conclusions:

• Etoposide's mechanism involves trapping DNA loops, impacting DNA structure and topology.
• Provides novel mechanistic insights into etoposide's effects on topoisomerase II dynamics.
• Highlights differences in DNA compaction and supercoil relaxation among topoisomerase II variants.