Book of Abstracts: Albany 2005
Structural Basis for Poisoning of Topoisomerase 1 by the Antitumor Drug Gemcitabine
Human Topoisomerase 1 (top1) regulates DNA superhelicity as required for DNA replication and transcription. Poisoning of top1 is responsible for the anticancer activity of the camptothecin class of anticancer drugs. We have shown previously that gemcitabine (2',2'-difluoro-2'-deoxycytidine) substitution alters the structure and stability of a model Okazaki fragment and that gemcitabine perturbs the cleavage/re-ligation equilibrium for a model top1 cleavage site. The model top1 cleavage site is a 28mer DNA duplex that undergoes efficient top1 catalyzed cleavage and re-ligation at a single site. We present NMR assignments for the top1 recognition site within the context of this 28mer DNA duplex. We also present an analysis of an extensive MD simulation of a top1:DNA complex with gemcitabine substituted at the +1 position relative to the site of top1 cleavage. These results will be used to rationalize the enhancement of top1 cleavage complex formation due to gemcitabine substitution.
References and Footnotes
William H. Gmeiner1,*
1Department of Cancer Biology