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Spatial organization of topoisomerase I-mediated DNA cleavage induced by camptothecin-oligonucleotide conjugates

Paola B Arimondo1, Stéphane Angenault, Ludovic Halby

  • 1Laboratoire de Biophysique, USM0503 Muséum National d'Histoire Naturelle, UMR8646 CNRS, UR565 INSERM, 43 Rue Cuvier, 75231 Paris Cedex 05, France. arimondo@mnhn.fr

Nucleic Acids Research
|July 11, 2003
PubMed

Insights

Triple helix-forming oligonucleotides conjugated with camptothecin selectively induce DNA cleavage via topoisomerase I. This targeted DNA damage is sequence-specific and depends on inhibitor positioning, offering insights into enzyme function.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Genetics

Background:

  • Triple helix-forming oligonucleotides (TFOs) can bind specific DNA sequences.
  • Topoisomerase I (Top1) is crucial for managing DNA topology during replication and transcription.
  • Camptothecin is a potent Top1 inhibitor used in cancer therapy.

Purpose of the Study:

  • To investigate the DNA cleavage efficiency of TFOs linked to camptothecin derivatives.
  • To determine the influence of camptothecin positioning (3' vs. 5') on Top1-mediated DNA cleavage.
  • To analyze the impact of cleavage site location within duplex DNA on TFO-conjugate activity.

Main Methods:

  • Synthesis of TFO-camptothecin conjugates with varying inhibitor positions.
  • Construction of 59 bp duplex DNA containing triplex binding sites.
  • Assays to measure Top1-mediated DNA cleavage at specific sites.

Main Results:

  • Sequence-specific DNA cleavage occurred only when camptothecin was attached to the 3'-end of the oligonucleotide and on the oligopyrimidine strand.
  • Cleavage was dependent on the inhibitor's position relative to the triplex binding site.
  • No targeted cleavage was observed with 5'-end conjugates, attributed to structural differences at the DNA junction.

Conclusions:

  • Camptothecin-TFO conjugates enable targeted Top1-mediated DNA cleavage.
  • The spatial organization of the Top1-DNA complex influences cleavage efficiency.
  • These conjugates are valuable tools for studying Top1 activity and DNA organization in cellular contexts.

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