Phleomycin induced
DNA breakage was investigated with superhelical Col. E1
DNA and linear T2
DNA as well. In both
DNA-forms besides single-strand breaks direct double-strand breaks were produced by the
drug. The double-strand breakage rate obtained
after treatment with
phleomycin, however, was considerably smaller than that found after
bleomycin treatment. Whereas the single- and double-strand breakage rate in Col. E1
DNA showed a linear and nearly quadratic dependence on the
phleomycin concentration, respectively, in T2
DNA the breakage rates increased faster than the first or second power of the concentration. This indicates various modes of
drug-
DNA interaction. Under nondegrading conditions a strong retardation of electrophoretic mobility was observed for all three topological isomers of Col. E1
DNA whereas the sedimentation behaviour remained unchanged. The in vitro effects (strand breakage) of
phleomycin and
bleomycin are compared with induction of
chromosomal aberrations in human lymphocytes and oocytes of Drosophila melanogaster.