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Chromatin dynamics in interphase

par Webmaster - 7 juillet 2007

Orateur :

Angelo Rosa, Institute for Biocomputation and Physics of Complex Systems, (BIFI), Zaragoza, Spain

Salle :


Sujet :

Genome of eukaryotes is organized in a set of several chromosomes which become visible during cell division, while the higher levels of DNA organization beyond the 30nm chromatin fiber appear to vanish during periodes of normal cell activity. Experimentally, the large-scale structure of decondensed chromosomes can be studied using Fluorescence in situ Hybridization (FISH) : nucleic acids are chemically modified to incorporate fluorescent probes and specific sequences on single cells can be detected. In particular, it is possible to determine locations of and spatial distances between targeted sites as well as to mark different portions of the genome (chromosome painting). We propose here that the recently observed three-dimensional spatial organization of chromosomes in interphase cell nuclei (territories) which is believed to play an important role in gene expression and regulation is related to the slow kinetics due to spatial constraints between different parts of the chain. We describe two different relaxation mechanisms for tails and core of chromosomes. Finally, we suggest a link with some results concerning equilibrium properties of semi-diluted solutions of unentangled ring polymers.

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