Analogous cleavage of DNA by micrococcal nuclease and a 1-10-phenanthroline-cuprous complex

We have examined the DNA cleavage specificity of a 1,10-phenanthroline-cuprous complex and find this agent to recognize the same sites and cleave with the same relative preferences as micrococcal nuclease. In contrast, DNase I and bleomycin-ferrous complex cleave the same 5000 bp D. melanogaster histone gene DNA with different specificities, although some of the sites appear to be recognized and cleaved by all four reagents. Our results suggest that the reagents used probably detect discrete conformational perturbations along the DNA double helix.