小柯机器人

近日，奥地利科学院Daniel W. Gerlich、Sara Cuylen-Haering等研究人员发现Ki-67引起的染色体簇在核组装期间参与移除胞浆。这一研究成果发表于2020年9月2日在线发表在《自然》上。

研究人员在HeLa细胞中发现大的细胞质成分在核被膜组装之前通过染色体向密集簇的移动而被置换。当染色体接近后期纺锤体的极点时，就会发生这种聚集，并由涉及表面活性剂样蛋白Ki-67的微管独立机制所介导。Ki-67在有丝分裂的早期阶段形成排斥性分子刷，但是在有丝分裂结束时，这些分子刷解离，并且Ki-67促进染色体聚集。研究人员表明有丝分裂后从核中移除成熟核糖体取决于Ki-67调控的染色体簇。因此，这项研究表明，染色体结构有助于在开放有丝分裂后重新建立真核细胞的区室化。

据介绍，真核生物中的基因表达需要从细胞质翻译中有效分离核转录和RNA加工。这种分离是通过核被膜实现的，其通过核孔的交换来控制大分子。但是，在有丝分裂期间，动植物细胞中的核被膜会分解，从而使细胞质和核成分相互混合。当核被膜被重塑后，通过受体介导的核孔转运将细胞质成分从核中去除。这些孔的大小为39纳米，这引发了如何从核中清除更大细胞质分子的问题。

附：英文原文

Title: Chromosome clustering by Ki-67 excludes cytoplasm during nuclear assembly

Author: Sara Cuylen-Haering, Mina Petrovic, Alberto Hernandez-Armendariz, Maximilian W. G. Schneider, Matthias Samwer, Claudia Blaukopf, Liam J. Holt, Daniel W. Gerlich

Issue&Volume: 2020-09-02

Abstract: Gene expression in eukaryotes requires the effective separation of nuclear transcription and RNA processing from cytosolic translation1. This separation is achieved by the nuclear envelope, which controls the exchange of macromolecules through nuclear pores2. During mitosis, however, the nuclear envelope in animal and plant cells disassembles, allowing cytoplasmic and nuclear components to intermix3. When the nuclear envelope is reformed, cytoplasmic components are removed from the nucleus by receptor-mediated transport through nuclear pores2. These pores have a size limit of 39 nanometres4,5,6,7, which raises the question of how larger cytoplasmic molecules are cleared from the nucleus. Here we show in HeLa cells that large cytoplasmic components are displaced before nuclear envelope assembly by the movement of chromosomes to a dense cluster. This clustering occurs when chromosomes approach the poles of anaphase spindles, and is mediated by a microtubule-independent mechanism that involves the surfactant-like protein Ki-67. Ki-67 forms repulsive molecular brushes during the early stages of mitosis8, but during mitotic exit the brushes collapse and Ki-67 promotes chromosome clustering. We show that the exclusion of mature ribosomes from the nucleus after mitosis depends on Ki-67-regulated chromosome clustering. Thus, our study reveals that chromosome mechanics help to re-establish the compartmentalization of eukaryotic cells after open mitosis.

DOI: 10.1038/s41586-020-2672-3

Source: https://www.nature.com/articles/s41586-020-2672-3

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