Activation of topoisomerase I by poly [ADP-ribose] polymerase.

P. I. Bauer, K. G. Buki, J. A. Comstock, E. Kun

Research output: Contribution to journalArticle

24 Citations (Scopus)


Poly(ADP-ribose) polymerase (PARP I) and Topoisomerase I (Topo I) were reisolated from calf thymus to eliminate cross contamination as tested by immunotransblots. The specific activity of Topo I was greatly increased by added PARP I, following saturation kinetics. Recombinant PARP I and isolated PARP I at final purity were indistinguishable in terms of their activation of Topo I. There was a coincidence of experimentally obtained binding constants and computer generated values based on the kinetic model, indicating that the association of PARP I and Topo I is rate limiting in the catalytic activation of Topo I by PARP I. Polypeptide domains of PARP I that are required for protein-protein binding and protein-DNA binding also activate Topo I. Fluorescence resonance energy transfer between fluorophor-labeled PARP I and Topo I was demonstrated. The binding of Topo I to circular SV40 DNA, assayed either by the formation of a) the sum of non-covalently and covalently attached Topo I to DNA or b) by the covalently bound transient intermediate in the presence of camptothecin, was augmented when PARP I protein was bound to SV40 DNA. These binding experiments provide a molecular basis for the kinetic activation of Topo I by PARP I inasmuch as the increased superhelicity of SV40 DNA induced by PARP I may facilitate the formation of a more <tight fisted> Topo I-DNA complex that increases the rate of the DNA breakage-reunion cycle of Topo I catalysis.

Original languageEnglish
Pages (from-to)533-540
Number of pages8
JournalInternational journal of molecular medicine
Issue number5
Publication statusPublished - May 2000

ASJC Scopus subject areas

  • Genetics

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