通过环挤压实现缠结聚合物流化
Fluidification of Entangled Polymers by Loop Extrusion
AI总结：
本研究通过模拟发现，环挤压因子（LEF）通过形成瓶刷状结构主动流化缠结线性聚合物，显著降低DNA缠结与有效粘度，并揭示其最佳作用密度及粘度与聚合物长度的线性标度关系。
摘要：
环挤压是贯穿细胞周期塑造染色体组织的主要过程之一，但其在调节DNA缠结与核质粘弹性方面的作用仍被忽视。我们模拟了在通用环挤压因子（LEF）作用下线性聚合物的缠结溶液，该模型充分考虑了拓扑约束和LEF-DNA不可交叉性。我们发现，挤压驱动了瓶刷状结构的形成，通过一种主动流化机制显著降低了系统的缠结和有效粘度。有趣的是，这种流化在每300-3000个碱基对一个LEF时达到最优。与缠结线性链形成鲜明对比的是，被挤压链的粘度与聚合物长度呈线性标度关系，产生高达1000倍的流化效果。我们的结果阐明了环挤压如何在体内主动调节基因组缠结和粘弹性。
英文摘要：
Loop extrusion is one of the main processes shaping chromosome organisation across the cell cycle, yet its role in regulating DNA entanglement and nucleoplasm viscoelasticity remains overlooked. We simulate entangled solutions of linear polymers under the action of generic Loop Extruding Factors (LEF) with a model that fully accounts for topological constraints and LEF-DNA uncrossability. We discover that extrusion drives the formation of bottle-brush-like structures which significantly lower the entanglement and effective viscosity of the system through an active fluidification mechanism. Interestingly, this fluidification displays an optimum at one LEF every 300-3000 basepairs. In marked contrast with entangled linear chains, the viscosity of extruded chains scales linearly with polymer length, yielding up to 1000-fold fluidification. Our results illuminate how loop extrusion contributes to actively modulate genome entanglement and viscoelasticity in vivo.
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