Induction of topoisomerase II-mediated DNA cleavage by a protoberberine alkaloid, berberrubine.

摘要: Topoisomerase II is the cytotoxic target for a number of clinically relevant antitumor drugs. Berberrubine, protoberberine alkaloid which exhibits activity in animal models, has been identified as specific poison topoisomerase vitro. II-mediated DNA cleavage assays showed that berberrubine poisons enzyme by stabilizing II-DNA cleavable complexes. Subsequent proteinase K treatments revealed berberrubine-induced was generated solely II. religation with elevated temperature substantial reduction induced berberrubine, to extent comparable other prototypical poison, etoposide, suggesting involves stabilization reversible enzyme-DNA complex. However, step at induces complex may differ from etoposide difference formation intermediate product, nicked DNA. This suggests berberrubine's primary mode linear involve trapping molecules, formed transition covalently closed circular Unwinding duplex consistent an intercalative binding this compound. In addition ability induce mediated II, high concentrations shown specifically inhibit catalytic activity. however, did not I up 240 microM. Cleavage sites presence and were mapped Berberrubine site-specific concentration-dependent manner. Comparison pattern they share many common cleavage. Taken together, these results indicate represents new class agent well inhibition have potential clinical value cancer treatment.