Dihydrotanshinone I induced topoisomerase I-mediated DNA cleavage in vitro as strongly as camptothecin, but topoisomerase II-mediated DNA cleavage was not affected. In a DNA relaxation assay using calf thymus DNA topoisomerase I and supercoiled pBR322 plasmid DNA, dihydrotanshinone I reduced topoisomerase I-mediated DNA relaxation in a dose-dependent manner. Heat treatment (65°C) of the reaction mixture containing dihydrotanshinone I and topoisomerase I resulted in a substantial reduction in DNA cleavage, suggesting topoisomerase I and dihydrotanshinone I may form a reversible cleavable complex to induce DNA damage. A DNA unwinding assay using T4 DNA ligase showed that dihydrotanshinone I is a very weak DNA intercalator. These results suggest that dihydrotanshinone I inhibits the catalytic activity of topoisomerase I by the formation of a cleavable complex and at least in part through the intercalation into DNA. © 1999, Taylor & Francis Group, LLC. All rights reserved.
CITATION STYLE
Lee, D. S., Lee, S. H., Kwon, G. S., Lee, H. K., Woo, J. H., Kim, J. G., & Hong, S. D. (1999). Inhibition of DNA Topoisomerase I by Dihydrotanshinone I, Components of a Medicinal Herb Salvia miltiorrhiza Bunge. Bioscience, Biotechnology and Biochemistry, 63(8), 1370–1373. https://doi.org/10.1271/bbb.63.1370
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