Fig. 6.

Nucleosomes under DNA supercoiling. a A schematic of the magnetic tweezers experiments to study nucleosome chiral transition. A nucleosome array was twisted and held under constant force while the DNA was supercoiled. b A model of the nucleosome chiral transition from left- to right-handed configuration. Two alternative routes for the refolding of the dimers are shown. c A drawing depicting the nucleosome-stretching assay with an AOT. A DNA containing a single nucleosome was stretched under a defined torsion. d A model for nucleosome turnover during transcription. (+) DNA supercoiling in front of a transcribing RNAP may induce H2A-H2B dimer loss, while (−) DNA supercoiling behind the RNAP facilitates nucleosome assembly and stabilizes assembled nucleosomes. a and b are adapted from Bancaud et al. (2007) and c from Sheinin et al. (2013) with permission