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

Int J Mol Med. 2000 May;5(5):533-40. doi: 10.3892/ijmm.5.5.533.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cattle
  • DNA Topoisomerases, Type I / isolation & purification
  • DNA Topoisomerases, Type I / metabolism*
  • DNA, Circular / metabolism
  • Energy Transfer
  • Enzyme Activation
  • Fluorescence
  • Kinetics
  • NAD / metabolism
  • Peptide Fragments / metabolism
  • Poly(ADP-ribose) Polymerases / isolation & purification
  • Poly(ADP-ribose) Polymerases / metabolism*


  • DNA, Circular
  • Peptide Fragments
  • NAD
  • Poly(ADP-ribose) Polymerases
  • DNA Topoisomerases, Type I