Enhancement and alteration of bleomycin-catalyzed site-specific DNA cleavage by distamycin A and some minor groove binders.

The effects of compounds which bind in the DNA minor groove of A.T rich sequences, on bleomycin-catalyzed site-specific DNA cleavage were investigated by a DNA sequencing technique. Distamycin A enhanced bleomycin-catalyzed DNA cleavage in G.C rich sequences such as 5'-GGGGC-3' (under scoring; the cleaved nucleotide). The cleavage in such a sequence in the presence of distamycin A was greater than that in the absence of distamycin A by as much as about 100 times. Neither Hoechst 33258, 4',6-diamidino-2-phenylindole (DAPI) nor berenil caused extensive enhancement. The results suggest that the distamycin-induced conformational changes of DNA through interactions other than the DNA minor groove binding in A.T-rich sequences are specifically suitable for the bleomycin action.