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首页> 外文期刊>Epigenetics & Chromatin >Sensitivity of cohesin–chromatin association to high-salt treatment corroborates non-topological mode of loop extrusion
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Sensitivity of cohesin–chromatin association to high-salt treatment corroborates non-topological mode of loop extrusion

机译：Cohyin-Chromatin与高盐处理的敏感性证实了环形挤出的非拓扑模式

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Cohesin is a key organizer of chromatin folding in eukaryotic cells. The two main activities of this ring-shaped protein complex are the maintenance of sister chromatid cohesion and the establishment of long-range DNA–DNA interactions through the process of loop extrusion. Although the basic principles of both cohesion and loop extrusion have been described, we still do not understand several crucial mechanistic details. One of such unresolved issues is the question of whether a cohesin ring topologically embraces DNA string(s) during loop extrusion. Here, we show that cohesin complexes residing on CTCF-occupied genomic sites in mammalian cells do not interact with DNA topologically. We assessed the stability of cohesin-dependent loops and cohesin association with chromatin in high-ionic-strength conditions in G1-synchronized HeLa cells. We found that increased salt concentration completely displaces cohesin from those genomic regions that correspond to CTCF-defined loop anchors. Unsurprisingly, CTCF-anchored cohesin loops also dissipate in these conditions. Because topologically engaged cohesin is considered to be salt resistant, our data corroborate a non-topological model of loop extrusion. We also propose a model of cohesin activity throughout the interphase, which essentially equates the termination of non-topological loop extrusion with topological loading of cohesin. This theoretical framework enables a parsimonious explanation of various seemingly contradictory experimental findings.
机译：Cohesin是真核细胞中染色蛋白折叠的关键组织者。这种环形蛋白质复合物的两个主要活性是通过环挤出过程维持姐妹染色体内聚力和建立远程DNA-DNA相互作用。虽然已经描述了凝聚力和环路挤出的基本原理，但我们仍然不了解几个重要的机制细节。这种未解决的问题之一是Cohesin环拓扑上拓扑在环挤出过程中的DNA串的问题。在这里，我们表明，驻留在哺乳动物细胞中的CTCF占用的基因组位点的休尼辛复合物不会拓扑上与DNA相互作用。我们评估了在G1同步HeLa细胞中的高离子强度条件下与染色质依赖于辛蛋白依赖环和幼曲蛋白的稳定性。我们发现，增加的盐浓度完全从对应于CTCF定义的环锚的那些基因组区域完全取代咖啡蛋白。不出所料，CTCF锚定的COLENIN环绕在这些条件下也消散。由于拓扑啮合的辅酶蛋白被认为是耐盐，我们的数据证实了环路挤出的非拓扑模型。我们还提出了整个相互作用的休素活动模型，其基本上等于与池内拓扑载荷的非拓扑环挤出终止。这种理论框架可以解释对各种看似矛盾的实验结果的解释。

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