小柯机器人

日本国家遗传学研究所Yasuto Murayama等研究人员利用纯化蛋白质观察黏连蛋白与DNA复制的协调性。2024年1月24日，《自然》杂志在线发表了这项成果。

研究人员利用纯化的蛋白质重建了一个功能性复制体，从而研究了黏连蛋白与复制之间的相互作用。一旦DNA在复制前被环绕，黏连蛋白环就会容纳从开始到终止的整个复制过程，从而对新合成的DNA进行拓扑捕获。这表明拓扑凝黏连蛋白负载是应对复制的关键分子先决条件。矛盾的是，拓扑加载本身对复制速度有很大的限制，而且在生理盐浓度下几乎不会发生。与复制体相关的内聚建立因子Chl1螺旋酶和Ctf4解决了这一矛盾，它们在持续复制过程中专门促进了黏连蛋白的加载。

因此，研究人员发现模拟DNA解旋状态的气泡DNA能诱导拓扑黏连蛋白加载，而Chl1能进一步促进黏连蛋白加载。因此，研究人员提出，当遇到由包括复制在内的酶活动驱动的解旋DNA结构时，黏连蛋白会将最初的静电DNA结合模式转换为拓扑拥抱模式。总之，这些研究结果表明了黏连蛋白最初是如何对复制做出反应的，并为姐妹染色单体内聚的建立提供了一个分子模型。

研究人员表示，在细胞分裂过程中，两个新复制的基因组DNA副本被环形的黏连蛋白复合物固定在一起，以确保基因组的忠实遗传。黏连蛋白在DNA复制过程中通过拓扑夹持两个姐妹DNA来介导姐妹染色单体的内聚，但人们对黏连蛋白如何在复制叉建立内聚还知之甚少。

附：英文原文

Title: Coordination of cohesin and DNA replication observed with purified proteins

Author: Murayama, Yasuto, Endo, Shizuko, Kurokawa, Yumiko, Kurita, Ayako, Iwasaki, Sanae, Araki, Hiroyuki

Issue&Volume: 2024-01-24

Abstract: Two newly duplicated copies of genomic DNA are held together by the ring-shaped cohesin complex to ensure faithful inheritance of the genome during cell division1,2,3. Cohesin mediates sister chromatid cohesion by topologically entrapping two sister DNAs during DNA replication4,5, but how cohesion is established at the replication fork is poorly understood. Here, we studied the interplay between cohesin and replication by reconstituting a functional replisome using purified proteins. Once DNA is encircled before replication, the cohesin ring accommodates replication in its entirety, from initiation to termination, leading to topological capture of newly synthesized DNA. This suggests that topological cohesin loading is a critical molecular prerequisite to cope with replication. Paradoxically, topological loading per se is highly rate limiting and hardly occurs under the replication-competent physiological salt concentration. This inconsistency is resolved by the replisome-associated cohesion establishment factors Chl1 helicase and Ctf4 (refs. 6,7), which promote cohesin loading specifically during continuing replication. Accordingly, we found that bubble DNA, which mimics the state of DNA unwinding, induces topological cohesin loading and this is further promoted by Chl1. Thus, we propose that cohesin converts the initial electrostatic DNA-binding mode to a topological embrace when it encounters unwound DNA structures driven by enzymatic activities including replication. Together, our results show how cohesin initially responds to replication, and provide a molecular model for the establishment of sister chromatid cohesion.

DOI: 10.1038/s41586-023-07003-6

Source: https://www.nature.com/articles/s41586-023-07003-6

Nature：《自然》，创刊于1869年。隶属于施普林格·自然出版集团，最新IF：69.504
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