Activation of DNA cleavage by dynemicin A in a B-Z conformational junction

We report here that the DNA strand scission by dynemicin A is not only sequence-specific but also conformation-specific. The salt-induced B----Z conformational transition dramatically enhanced the cleavage by dynemicin A in a B-Z junction region. By contrast, the bleomycin-Fe(II) complex, the elsamicin A-Fe(II) complex, and esperamicin A1 did not induce any preferential DNA cutting in such a DNA structure. The characteristic hyperreactivity of dynemicin A is observed in (dC-dG)8- and (dC-dG)12-inserted DNAs, but not in (dC-dG)5-inserted DNA. These results suggest value in the use of dynemicin A as proof of the existence of a B-Z junction in vivo and also may aid in understanding the structure of B-Z junctions.