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Related Experiment Videos

Interactions between eukaryotic DNA topoisomerase I and a specific binding sequence.

T Stevnsner1, U H Mortensen, O Westergaard

  • 1Department of Molecular Biology and Plant Physiology, University of Arhus, Denmark.

The Journal of Biological Chemistry
|June 15, 1989
PubMed
Summary

Eukaryotic DNA topoisomerase I binds tightly to specific DNA sequences through noncovalent interactions, not transient covalent bonds. This strong binding determines substrate preference and enzyme activity.

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Area of Science:

  • Molecular Biology
  • Enzymology
  • Genetics

Background:

  • Eukaryotic DNA topoisomerase I is crucial for managing DNA topology during replication and transcription.
  • Understanding enzyme-substrate interactions is key to elucidating DNA processing mechanisms.

Purpose of the Study:

  • To investigate the binding interaction between eukaryotic DNA topoisomerase I and its high-affinity DNA sequence.
  • To determine the contributions of noncovalent and covalent interactions to enzyme-DNA binding specificity.

Main Methods:

  • Quantitative footprinting analysis to assess enzyme binding.
  • DNA modification interference assays to identify essential bases for binding.
  • Analysis of enzyme-DNA complex structure and stability.

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Main Results:

  • Topoisomerase I exhibits substrate preference due to strong, specific noncovalent binding to target DNA sequences.
  • A tight noncovalent association, not the transient covalent intermediate, confers binding specificity.
  • The enzyme protects a 20-base pair region, with essential bases primarily located 5' of the cleavage site on the scissile strand.

Conclusions:

  • The high affinity of DNA topoisomerase I for specific sequences is primarily mediated by noncovalent interactions.
  • The enzyme's specificity is dictated by the precise recognition of DNA bases within a defined binding region.
  • These findings clarify the molecular basis of DNA topoisomerase I-DNA recognition and substrate selection.