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arXiv · 0708.0156

Nucleosome Chiral Transition under Positive Torsional Stress in Single Chromatin Fibers

Aurelien Bancaud·Gaudeline Wagner·Natalia Conde e Silva·Christophe Lavelle·Hua Wong·Julien Mozziconacci·Maria Barbi·Andrei Sivolob·Eric Le Cam·Liliane Mouawad·Jean-Louis Viovy·Jean-Marc Victor·Ariel Prunell
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Abstract

Using magnetic tweezers to investigate the mechanical response of single chromatin fibers, we show that fibers submitted to large positive torsion transiently trap positive turns, at a rate of one turn per nucleosome. A comparison with the response of fibers of tetrasomes (the (H3-H4)2 tetramer bound with ~50 bp of DNA) obtained by depletion of H2A-H2B dimers, suggests that the trapping reflects a nucleosome chiral transition to a metastable form built on the previously documented righthanded tetrasome. In view of its low energy, <8 kT, we propose this transition is physiologically relevant and serves to break the docking of the dimers on the tetramer which in the absence of other factors exerts a strong block against elongation of transcription by the main RNA polymerase.

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Aurelien Bancaud, Gaudeline Wagner, Natalia Conde e Silva, Christophe Lavelle, Hua Wong, Julien Mozziconacci, Maria Barbi, Andrei Sivolob, Eric Le Cam, Liliane Mouawad, Jean-Louis Viovy, Jean-Marc Victor, Ariel Prunell. 2007-08-01. Nucleosome Chiral Transition under Positive Torsional Stress in Single Chromatin Fibers. https://doi.org/10.1016/j.molcel.2007.05.037

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