Origin of sequence specific cleavage of DNA by bleomycins.

A new DNA photocleaving agent which contains bleomycin A2's DNA binding portion and its mono- and terthiazole analogues have been designed and synthesized, and their DNA binding mode and cleavage base specificity have been studied. The photoactive p-nitrobenzoyl group attached at the end of molecules cleaves DNA on UV irradiation. All the oligo-thiazole compounds exhibited high sequence specificity in DNA scission. The bithiazole derivative did not cleave DNA at or near 5'-GpT-3' or 5'-GpC-3' as expected from widely believed DNA binding mechanism of the antibiotics.