Supercoil-induced Z-DNA formation within 5'-end of chicken myb proto-oncogene.

We have analyzed the recently sequenced and characterized 2.9 kb fragment derived from the 5'-end of chicken myb proto-oncogene with respect to structural perturbations induced by DNA supercoiling. Within the first intron a 50 bp sequence stretch was localized, starting approximately 450 nucleotides downstream from putative ATG initiation codon, which forms a non-B-DNA structure. Fine mapping with structural probes revealed the three adjacent regions with imperfect purine-pyrimidine alternation creating together relatively long Z-forming tract, parts of which may undergo a B-Z DNA transition at different superhelical densities.