Interaction of bleomycin with DNA.

The sequence of oligonucleotides produced by the action of bleomycin and ferrous ion on double- and single-stranded DNA has been determined. In the presence of ferrous ion, bleomycin promotes cleavage at G-T and G-C sequences, while high concentrations of ferrous ion alone result in strand scission that is not base specific. In the presence of bleomycin and ferrous ion, pyrimidine bases located to the 3' side of guanosine are released preferentially and a low molecular weight product that forms a chromophore with thiobarbituric acid is produced from the deoxyribose moiety. Oligonucleotides produced by the action of bleomycin differ slightly in electrophoretic mobility from those produced by chemical or enzymatic cleavage. A model is proposed to explain the interactions of bleomycin with DNA.