> seminars/symposia > past seminars/symposia : Friday, October 26, 2007

Chromatin Modeling and Simulation: A Tale of Histone Tails

by

Tamar Schlick
New York University

Friday, October 26, 2007
3:30 p.m.
101 Walter Library

Eukaryotic chromatin is the fundamental protein/nucleic acid unit that stores the genetic material. Understanding how chromatin fibers fold and unfold is important for interpreting fundamental biological processes like DNA replication and transcription regulation. Using a mesoscopic model of oligonucleosome chains and tailored sampling protocols, we elucidate the energetics of oligonucleosome folding/unfolding and the role of each histone tail in regulating chromatin structure. Simulations reveal unfolding of oligonucleosome at low salt due to strong electrostatic repulsion between linker DNAs and moderate folding at higher salt due to a balance between the attractive inter-nucleosomal interactions (mediated by the histone tails) and repulsive interactions between the linker DNA. Furthermore, tail-mediated fiber/fiber interactions emerge as the oligonucleosome chain folds into more compact self interactions. Analyses of the tail positional distributions reveal a broad spread of tail positions consistent with the dynamic and flexible nature of the tails and the role of each tail in folding and energetics. These studies open the door to investigations of higher-order structures of compact chromatin and the biochemical modulation of chromatin structure by altered histone tail charge.

Of possible interest:

• T Schlick, Molecular Modeling: An Interdisciplinary Guide, Springer-Verlag, New York, 2002;
• D. Beard and T. Schlick, Structure 9: 105–114 (2001);
• G. Arya et al., Biophys. J. 91: 133–150 (2006);
• G. Arya & T. Schlick, Proc. Natl. Acad. Sci. 103: 16236–16241 (2006);
• G. Arya & T. Schlick, J. Chem. Phys. 126: 044107 (2007).

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