Berlin 2005 – scientific programme

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AKB: Biologische Physik

AKB 45: Single Molecule Biophysics

AKB 45.5: Talk

Monday, March 7, 2005, 15:45–16:00, TU H2013

Tail Induced Interactions of Nucleosome Core Particles — •Christian Holm, Frank Mülbacher, and Helmut Schiessel — Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz

We present a MD simulation study of the interactions between nucleosome core particles (NCPs). Each NCP consists of a core of eight histone proteins and a strand of DNA, which is wrapped around about two times. Special emphasis was placed on the role of the histone tails. We model the histone core and the wrapped DNA by a charged sphere, while the histone tails are represented by oppositely charged polyelectrolyte chains grafted onto the sphere’s surface, interacting via a Debye-Hückel potential. We find that the effect of tail bridging between the spheres does indeed account for the observed attraction, thus reproducing the qualitative features of the experimental results. We further modify our model to use either only one interacting tail, or charge patches instead of the tails in order to isolate the quantitative features of the tail interactions. The reduction of the charge fraction of the tails, that corresponds to the process of acetylation, leads to a reduction or even the disappearance of the attraction, which subsequently can lead to the unfolding of the chromatin fiber, thereby activating genes.