Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session K49: Physics of Genome Organization: From DNA to Chromatin I
8:00 AM–10:48 AM,
Wednesday, March 7, 2018
LACC Room: 511A
Sponsoring Units: DBIO DPOLY GSNP
Chair: Ralf Bundschuh, Ohio State University
Abstract: K49.00001 : Nucleosome unwrapping may be easier than you think*
8:00 AM–8:36 AM
Nucleosome unwrapping is essential in order to provide access to eukaryotic DNA otherwise tightly wrapped into nucleosomes. Unwrapping several tens of base pairs from one side of the nucleosome is known to require several kT of free energy. Here we show that for a nucleosome that is fixed on both ends such as in the context of higher order chromatin structure, changes in the end-to-end distance by tens of base pairs are possible at a free energy cost of only a few kT due to the entropic contribution of both ends of the nucleosomes unwrapping simultaneously. We derive this result in the context of quantitatively modeling recently published experimental data on nucleosomes attached to a DNA origami caliper and verify our model through analogous experiments on hexasomes, nucleosomes that are missing one of their histone heterodimers.
*This material is based upon work in collaboration with D. Zhao, J. Le, M. Darcy, M. Poirier, and C. Castro and supported by the NSF under Grants No. 1410172, 1516976, 1719316 and the NIH under Grants No. R01-GM083055 and R21-CA174583.
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