G-quadruplexes on chromosomal DNA negatively regulates topoisomerase 1 activity

Nucleic Acids Res. 2024 Mar 21;52(5):2142-2156. doi: 10.1093/nar/gkae073.

Abstract

Human DNA topoisomerase 1 (Top1) is a crucial enzyme responsible for alleviating torsional stress on DNA during transcription and replication, thereby maintaining genome stability. Previous researches had found that non-working Top1 interacted extensively with chromosomal DNA in human cells. However, the reason for its retention on chromosomal DNA remained unclear. In this study, we discovered a close association between Top1 and chromosomal DNA, specifically linked to the presence of G-quadruplex (G4) structures. G4 structures, formed during transcription, trap Top1 and hinder its ability to relax neighboring DNAs. Disruption of the Top1-G4 interaction using G4 ligand relieved the inhibitory effect of G4 on Top1 activity, resulting in a further reduction of R-loop levels in cells. Additionally, the activation of Top1 through the use of a G4 ligand enhanced the toxicity of Top1 inhibitors towards cancer cells. Our study uncovers a negative regulation mechanism of human Top1 and highlights a novel pathway for activating Top1.

MeSH terms

  • DNA / chemistry
  • DNA Replication
  • DNA Topoisomerases, Type I* / metabolism
  • G-Quadruplexes*
  • Humans
  • Ligands
  • Topoisomerase I Inhibitors / pharmacology
  • Transcription, Genetic*

Substances

  • DNA
  • DNA Topoisomerases, Type I
  • Ligands
  • Topoisomerase I Inhibitors
  • TOP1 protein, human