Effects of the DNA intercalators 4'-(9-acridinylamino)methanesulfon-m-anisidide and 2-methyl-9-hydroxyellipticinium on topoisomerase II mediated DNA strand cleavage and strand passage

Abstract

DNA topoisomerase II is believed to be the enzyme that produces the protein-associated DNA strand breaks observed in mammalian cell nuclei treated with various intercalating agents. Two intercalators--4'-(9-acridinylamino)methanesulfon-m-anisidide (m-AMSA, amsacrine) and 2-methyl-9-hydroxyellipticinium (2-Me-9-OH-E+)--differ in their effects on protein-associated double-strand breaks in isolated nuclei. m-AMSA stimulates their production at all concentrations, whereas 2-Me-9-OH-E+ stimulates at low concentrations and inhibits at high concentrations. We have reproduced these differential effects in experiments carried out in vitro with purified L1210 DNA topoisomerase II, and we have found that concentrations of 2-Me-9-OH-E+ above 5 microM prevent the trapping of DNA-topoisomerase II cleavable complexes irrespective of the presence of m-AMSA. It also stimulated topoisomerase II mediated DNA strand passage, again with or without inhibitory amounts of m-AMSA (this result suggests that extensive intercalation by 2-Me-9-OH-E+ destabilized the cleavable complexes). From these data, it is concluded that intercalator-induced protein-associated DNA strand breaks observed in intact eukaryotic cells and isolated nuclei are generated by DNA topoisomerase II and that intercalators can affect mammalian DNA topoisomerase II in more than one way. They can trap cleavable complexes and inhibit DNA topoisomerase II mediated DNA relaxation (m-AMSA and low concentrations of 2-Me-9-OH-E+) or destabilize cleavable complexes and stimulate DNA relaxation (high concentrations of 2-Me-9-OH-E+).

Newly Identified Antibacterial Compounds Are Topoisomerase Poisons in African Trypanosomes

“…Some intercalators inhibit topoisomerases without poisoning them, as seen with 4Ј-(9-acridinylamino)-methanesulfon-o-anisidide (o-AMSA). Others, such as the closely related isomer m-AMSA, poison topoisomerase II, promote the formation of double-stranded breaks, and are clinically useful antitumor agents (17,19,20). 2-Methyl-9-hydroxyellipticinium (2-Me-9-OH-E ϩ ), another intercalator, has an effect similar to what we observe for 1895 and 0020: low concentrations stimulate cleavable complex formation by topoisomerase II, but at higher concentrations the trapping of topoisomerase II is reduced (19,20).…”

Mode of action of thiocoraline, a natural marine compound with anti-tumour activity

“…daunomycin, doxorubicin). Since the mechanism of cytotoxicity of anthracyclines appears related to their ability to poison DNA Topoisomerase II enzyme we hypothesized that thiocoraline could act by the same mechanism of action and cause DNA breakage (Pommier et al, 1985;Capranico et al, 1990). However, thiocoraline did not inhibit DNA Topoisomerase II catalytic activity nor did it stimulate topoisomerase-mediated DNA cleavage in vitro.…”

Use of in vitro topoisomerase II assays for studying quinolone antibacterial agents

“…The topoisomerase 1I-mediated cleavage of DNA by CP-67,015 is consistent with its reported clastogenic effect on DNA in cell culture and its positive mutagenic response in mouse lymphoma cells. In vitro topoisomerase II catalytic and cleavage assays are useful for gaining preliminary information concerning the possible interaction(s) of some quinolones with eucaryotic topoisomerase II which may relate directly to their safety (mutagenicity, clastogenicity, or both) in human and veterinary medicinal usage.In vitro DNA cleavage mediated by mammalian topoisomerase II has been reported to occur (in the absence of drug) at high enzyme to DNA ratios (17,19) and to be enhanced by antitumor compounds such as 4'-(9-acridinylamino)methanesulfon-m-aniside (m-AMSA), ellipticine, 4,22,24,29,30,39). At the same time, these compounds have shown variable inhibitory effects on the catalytic activity of the enzyme (2, 4, 29).…”

“…In vitro DNA cleavage mediated by mammalian topoisomerase II has been reported to occur (in the absence of drug) at high enzyme to DNA ratios (17,19) and to be enhanced by antitumor compounds such as 4'-(9-acridinylamino)methanesulfon-m-aniside (m-AMSA), ellipticine, 4,22,24,29,30,39). At the same time, these compounds have shown variable inhibitory effects on the catalytic activity of the enzyme (2, 4, 29).…”

“…At the same time, these compounds have shown variable inhibitory effects on the catalytic activity of the enzyme (2,4,29). Since this class of drugs has also been associated with DNA breakage observed in cell culture, it has been suggested that enhanced topoisomerase II-mediated DNA cleavage is an important mechanism for the antitumor effects of these agents (4,6,20,21,24).…”