Abstract
Poly(ADP-ribose) polymerase (PARP)-1 was reported to promote the religation activity of topoisomerase I in the presence of camptothecin by itself through the direct interaction with topoisomerase I or by the formation of poly(ADP-ribosyl)ated topoisomerase I. We have demonstrated previously that ATP inhibited PARP-1/NAD-facilitated religation of topoisomerase I-linked DNA (TLD) in the presence of camptothecin. The mechanism of action was further studied in the present work. ATP as well as other nucleotides, including CTP, UTP, and GTP, had no effect on topoisomerase I cleavage and religation activities in the absence of camptothecin. In the presence of camptothecin or its derivative topotecan, ATP (at up to 2 mM) inhibited PARP-1/NAD-facilitated TLD religation in a dose-dependent manner. This could be due to the suppression of topoisomerase I poly(ADP-ribosyl)ation through the competition with NAD for the binding site(s) on PARP-1. The interaction between ATP and PARP-1 was independent of ATP hydrolysis. Study of different nucleotide analogs revealed that the structure could determine the dose response of nucleotides. In addition, it was noted that higher concentrations of ATP and CTP (at 2.5 mM or higher) promoted DNA religation by a PARP-1-independent mechanism. Our study implies the possible role of ATP and other nucleotides in the regulation of topoisomerase I activity in the presence of camptothecin analogs.
Footnotes
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This study is supported in part by National Institutes of Health grant CA97750-01 and CA634770, and the University of Hong Kong Seed Funding Programme for Basic Research. Y.-C.C. is a fellow of the National Foundation for Cancer Research.
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S.-Y.P. and C.-H.L. contributed equally to this work.
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ABBREVIATIONS: TLD, topoisomerase I-linked DNA; PARP, poly(ADP-ribose) polymerase; ApnA, diadenosine polyphosphate; adenyl-5′-yl imidodiphosphate; 2′-ara-ATP, 2′-9β-d-arabinofuranosyladenine 5′-triphosphate; ON, oligonucleotide; PAR, poly(ADP-ribose); camptothecin; TPT, topotecan.
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↵1 Current affiliation: Korea Institute of Toxicology, Yuseong, Daejeon, Korea.
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↵2 Current affiliation: Department of Chemistry, The University of Hong Kong, Hong Kong.
- Received December 17, 2007.
- Accepted March 18, 2008.
- The American Society for Pharmacology and Experimental Therapeutics
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