B-DNA and Z-DNA mononucleosome templates. a. Two series of templates were used for mononucleosome assembly: 140 bp and 177 bp. Each series consists of B-DNA without GC repeats (T140 and T177), B-DNA with GC repeats (B140 and B177) and Z-DNA (Z140 and Z177). All DNAs were generated by PCR amplification of the same parental vector. A PCR primer with GC repeats was used to generate the B-DNA-GC fragment; a primer with 8-me-guanine modified GC repeats was used to generate the Z-DNA fragment. b. Body-labeled PCR fragments described in 1a were challenged with Zaa-Fok (a fusion protein consisting of two highly specific Z-DNA binding domains, Zα, from ADAR1 and the catalytic domain of the restriction enzyme FokI) to assess Z-DNA stability. Arrow heads indicate the cleavage products.