Nucleic Acids Research Advance Access published online on June 10, 2008
Nucleic Acids Research, doi:10.1093/nar/gkn334
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Structural Biology |
The modulation of topoisomerase I-mediated DNA cleavage and the induction of DNA–topoisomerase I crosslinks by crotonaldehyde-derived DNA adducts
1Laboratory of Molecular Pharmacology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892 and 2Department of Chemistry, Center in Molecular Toxicology, Vanderbilt University, Nashville, TN 37235, USA
*To whom correspondence should be addressed. Tel: +1 301 496 5944; Fax: +1 301 402 0752; Email: pommier{at}nih.gov
Received January 28, 2008. Revised April 17, 2008. Accepted May 10, 2008.
Crotonaldehyde is a representative 
,β-unsaturated aldehyde endowed of mutagenic and carcinogenic properties related to its propensity to react with DNA. Cyclic crotonaldehyde-derived deoxyguanosine (CrA-PdG) adducts can undergo ring opening in duplex DNA to yield a highly reactive aldehydic moiety. Here, we demonstrate that site-specifically modified DNA oligonucleotides containing a single CrA-PdG adduct can form crosslinks with topoisomerase I (Top1), both directly and indirectly. Direct covalent complex formation between the CrA-PdG adduct and Top1 is detectable after reduction with sodium cyanoborohydride, which is consistent with the formation of a Schiff base between Top1 and the ring open aldehyde form of the adduct. In addition, we show that the CrA-PdG adduct alters the cleavage and religation activities of Top1. It suppresses Top1 cleavage complexes at the adduct site and induces both reversible and irreversible cleavage complexes adjacent to the CrA-PdG adduct. The formation of stable DNA–Top1 crosslinks and the induction of Top1 cleavage complexes by CrA-PdG are mutually exclusive. Lastly, we found that crotonaldehyde induces the formation of DNA–Top1 complexes in mammalian cells, which suggests a potential relationship between formation of DNA–Top1 crosslinks and the mutagenic and carcinogenic properties of crotonaldehyde.