小柯机器人

德国慕尼黑大学Christoph F. Kurat研究团队揭示复制起始处染色质组织的建立和功能。2023年4月5日，《自然》杂志在线发表了这项成果。

研究人员表示，起始识别复合物（ORC）对真核生物染色体复制的启动至关重要，因为它在复制起始点装载复制螺旋酶——小染色体维持（MCM）复合物。复制起始点显示出一种立体的核糖体组织，在ORC结合点有核糖体耗竭，侧面是间隔规则的核糖体阵列。然而，这种核糖体组织是如何建立的，以及这种组织是否是复制所需要的，仍然是未知的。

研究人员利用具有大约300个复制起始点的基因组规模的生化重组，从芽殖酵母中筛选了17个纯化的染色质因子，发现ORC通过协调染色质重塑剂INO80、ISW1a、ISW2和Chd1在复制起始点和侧翼核糖体阵列上建立核糖体耗竭。ORC的核糖体组织活动的功能重要性被orc1突变所证明，该突变保持了经典的MCM装载器活性，但废除了ORC的阵列生成活性。这些突变在体外损害了通过染色质的复制，在体内则是致命的。这些研究结果表明，ORC除了作为MCM装载器的典型作用外，还具有第二个关键功能，即作为复制起始点核糖体组织的核心调控者，这是高效染色体复制的重要前提。

附：英文原文

Title: Establishment and function of chromatin organization at replication origins

Author: Chacin, Erika, Reusswig, Karl-Uwe, Furtmeier, Jessica, Bansal, Priyanka, Karl, Leonhard A., Pfander, Boris, Straub, Tobias, Korber, Philipp, Kurat, Christoph F.

Issue&Volume: 2023-04-05

Abstract: The origin recognition complex (ORC) is essential for initiation of eukaryotic chromosome replication as it loads the replicative helicase—the minichromosome maintenance (MCM) complex—at replication origins1. Replication origins display a stereotypic nucleosome organization with nucleosome depletion at ORC-binding sites and flanking arrays of regularly spaced nucleosomes2,3,4. However, how this nucleosome organization is established and whether this organization is required for replication remain unknown. Here, using genome-scale biochemical reconstitution with approximately 300 replication origins, we screened 17 purified chromatin factors from budding yeast and found that the ORC established nucleosome depletion over replication origins and flanking nucleosome arrays by orchestrating the chromatin remodellers INO80, ISW1a, ISW2 and Chd1. The functional importance of the nucleosome-organizing activity of the ORC was demonstrated by orc1 mutations that maintained classical MCM-loader activity but abrogated the array-generation activity of ORC. These mutations impaired replication through chromatin in vitro and were lethal in vivo. Our results establish that ORC, in addition to its canonical role as the MCM loader, has a second crucial function as a master regulator of nucleosome organization at the replication origin, a crucial prerequisite for efficient chromosome replication.

DOI: 10.1038/s41586-023-05926-8

Source: https://www.nature.com/articles/s41586-023-05926-8

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
官方网址：http://www.nature.com/
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