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Apurinic sites are position-specific topoisomerase II poisons

P S Kingma1, N Osheroff

  • 1Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146, USA.

The Journal of Biological Chemistry
|January 10, 1997
PubMed

Insights

DNA lesions, specifically apurinic sites, act as endogenous topoisomerase II poisons. These DNA lesions enhance DNA cleavage activity, impacting anticancer drug mechanisms.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Genetics

Background:

  • Topoisomerase II is a crucial enzyme for DNA replication and repair.
  • Many anticancer drugs function by "poisoning" topoisomerase II, increasing its DNA-cleavage activity.
  • Endogenous DNA lesions may also influence topoisomerase II activity.

Purpose of the Study:

  • To investigate whether apurinic sites, a common DNA lesion, function as endogenous topoisomerase II poisons.
  • To characterize the impact of the position of apurinic sites on topoisomerase II activity.

Main Methods:

  • Site-specific introduction of apurinic sites into DNA substrates.
  • Biochemical assays to measure topoisomerase II-mediated DNA cleavage.
  • Analysis of DNA cleavage products and enzyme kinetics.

Main Results:

  • Apurinic sites located within the 4-base overhang of DNA scission stimulated topoisomerase II cleavage 10-18 fold.
  • The specificity of topoisomerase II was not altered by these lesions.
  • Apurinic sites outside the cleavage overhang inhibited enzyme activity.
  • The DNA breaks generated were double-stranded, protein-linked, and reversible.

Conclusions:

  • Apurinic sites function as position-specific poisons of topoisomerase II.
  • This finding provides a mechanism for how endogenous DNA damage influences topoisomerase II.
  • A unifying model for endogenous and exogenous topoisomerase II poisons is proposed, relevant to anticancer drug action.

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