Feb 1, 1976

Studies related to antitumor antibiotics. Part V. Reactions of mitomycin C with DNA examined by ethidium fluorescence assay

Canadian Journal of Biochemistry
J W LownA R Morgan

Abstract

The cytotoxic action of the antitumor antibiotic mitomycin C occurs primarily at the level of DNA. Using highly sensitive fluorescence assays which depend on the enhancement of ethidium fluorescence only when it intercalates duplex regions of DNA, three aspects of mitomycin C action on DNA have been studied: (a) cross-linking events, (b) alkylation without necessarily cross-linking, and (c) strand breakage. Cross-linking of DNA is determined by the return of fluorescence after a heat denaturation step at alkaline pH's. Under these conditions denatured DNA gives no fluorescence. The cross-linking was independently confirmed by S1-endonuclease (EC 3.1.4.-) digestion. At relatively high concentrations of mitomycin the suppression of ethidium fluorescence enhancement was shown not to be due to depurination but rather to alkylation, as a result of losses in potential intercalation sites. A linear relationship exists between binding ratio for mitomycin and loss of fluorescence. The proportional decrease in fluorescence with pH strongly suggests that the alkylation is due to the aziridine moiety of the antibiotic under these conditions. A parallel increase in the rate and overall efficiency of covalent cross-linking of DNA with lower ...Continue Reading

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Mentioned in this Paper

Novidium
Endonuclease
Fluorescence Spectroscopy
Alkaline DNase
LXN
Spectrophotometry, Ultraviolet
QPCT
Bos indicus
CAT
Hydrogen-Ion Concentration

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