Riposo Julien, Mozziconacci Julien
Université Pierre et Marie Curie, Laboratoire de Physique Théorique de la Matière Condensée, CNRS UMR 7600, 4, place Jussieu, 75005 Paris, France.
Mol Biosyst. 2012 Apr;8(4):1172-8. doi: 10.1039/c2mb05407h. Epub 2012 Jan 23.
Nucleosomes are regularly spaced along eukaryotic genomes. In the emerging model, known as "statistical positioning", this spacing is due to steric repulsion between nucleosomes and to the presence of nucleosome excluding barriers on the genome. However, new experimental evidence recently challenged the "statistical positioning" model (Z. Zhang et al., Science, 2011, 332(6032), 977-980). We propose here that the regular spacing can be better explained by adding attractive interactions between nucleosomes. In our model those attractions are due to the fact that nucleosomes are stacked in regular chromatin fibers. In a self-reinforcing mechanism, regular nucleosome spacing promotes in turn nucleosome stacking. We first show that this model can precisely account for the nucleosome spacing observed in Saccharomyces cerevisiae. We then use a simple toy model to show that attraction between nucleosomes can fasten the formation of the chromatin fiber.
核小体沿真核生物基因组规则排列。在新出现的被称为“统计定位”的模型中，这种间距是由于核小体之间的空间排斥以及基因组上存在排除核小体的屏障。然而，最近新的实验证据对“统计定位”模型提出了挑战（Z. Zhang等人，《科学》，2011年，332(6032)，977 - 980）。我们在此提出，通过增加核小体之间的吸引相互作用可以更好地解释这种规则间距。在我们的模型中，这些吸引力源于核小体堆叠在规则的染色质纤维中。在一种自我强化机制中，规则的核小体间距反过来又促进核小体堆叠。我们首先表明，该模型能够精确解释在酿酒酵母中观察到的核小体间距。然后我们使用一个简单的简化模型来表明核小体之间的吸引力能够加速染色质纤维的形成。
