Significance of Knotted Structures for Function of Proteins and Nucleic Acids - September 17-21, 2014

Significance of Knotted Structures for Function of Proteins and Nucleic Acids

Poster Session I

5 – POS Board 5 Topology of Eukaryotic Chromatin Dominika Borek , Zbyszek Otwinowski. UT Southwestern Medical Center, Dallas, TX, USA.

How nucleosomes are arranged into higher-order structures in vivo is not understood, even though the efficiency, precision, and microscopic images of metaphase chromosomes imply a high level of structural organization. The current views of higher-order eukaryotic chromatin organization involve either nucleosomal particles self-organizing by association and in a hierarchical manner into higher-order structures or postulate the presence of polymer-melt with ill-defined properties. Neither model agrees with the observed mechanical properties of chromatin, nor with microscopic in situ and in vitro observations of chromatin in its native state, nor with the distributive character of chromatids’ individualization. We have re-analyzed published observations and experimental data from the last 50 years of work on eukaryotic chromatin, looking for consistency with expanded biological knowledge. We propose a new model of eukaryotic chromatin organization, where the higher-order structure of chromatin is organized not only by proteins but also by DNA-based topological restraints that are formed in kinetically controlled processes. Modifications of nucleosomal particles play an important role in this model, serving as memory markers for remodeling complexes. The proposed organization of eukaryotic chromatin agrees well with experimental data and explains the specificity of distant cis-acting elements in transcription.

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