Figure 3.

Scheme of conformational rearrangement of chromatin ring or loop from transcriptionally inactive state (A) to transcriptionally active one (B). Cooperative nucleosome unfolding is accompanied by conformational transition of DNA into transcriptionally active A-form. (This is a summary from described experiments with SV40 and yeast minichromosomes also tangible for giant chromatin loops in eukaryotic chromosomes.).