Orateur
Prof.
Ralf Everaers
(Laboratoire de Physique et Centre Blaise Pascal, ENS-Lyon et CNRS)
Description
During interphase chromosomes decondense, but fluorescent in situ hybridization experiments reveal the existence of distinct territories occupied by individual chromosomes inside the nuclei of most eukaryotic cells. We use computer simulations to show that the existence and stability of territories is a kinetic effect that can be explained without invoking an underlying nuclear scaffold or protein-mediated interactions between DNA sequences. In particular, we show that the experimentally observed territory shapes, FISH observations on spatial distances between marked chromosome sites as well as 3-/Hi-C data for contact probabilities for human, Drosophila, and budding yeast chromosomes can be reproduced by a parameter-free minimal model of decondensing chromosomes. Our results suggest that the observed interphase structure and dynamics are due to generic polymer effects: confined Brownian motion conserving the local topological state of long chain molecules and segregation of mutually unentangled chains due to topological constraints. Understanding the statistical physics of the corresponding equilibrium system, unentangled melts of unconcatenated ring polymers, remains a challenge.
