Ki-67 is a PP1-interacting protein that organises the mitotic chromosome periphery.
Ki-67 is a PP1-interacting protein that organises the mitotic chromosome periphery.
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DOI：
10.7554/elife.01641
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发表时间：
2014-05-27
期刊：
影响因子：
7.7
通讯作者：
Vagnarelli P
中科院分区：
文献类型：
--
作者：
Booth DG;Takagi M;Sanchez-Pulido L;Petfalski E;Vargiu G;Samejima K;Imamoto N;Ponting CP;Tollervey D;Earnshaw WC;Vagnarelli P
当核仁在开放有丝分裂期间解体时，许多核仁蛋白质和RNA与染色体结合，建立覆盖染色体外周的染色体周区室。目前还不清楚这种特征不明显的隔室的功能。在这项研究中，我们报告说，核仁蛋白Ki-67所需的装配在人类细胞中的染色体周围区室。Ki-67是一种细胞周期调节蛋白磷酸酶1结合蛋白，参与核仁蛋白B23/核磷蛋白的磷酸化调节。在Ki-67、NIFK、B23、核仁素和四种新的染色体外周蛋白的siRNA耗尽后，它们都不能与人类染色体的外周结合。相关的光学和电子显微镜（CLEM）图像表明，几乎完全丧失了整个染色体周围区室。在缺乏染色体周室的情况下，有丝分裂染色体凝聚和内在结构似乎正常，但在有丝分裂后细胞中观察到核仁重组和核组织的显着差异。DOI：http://dx.doi.org/10.7554/eLife.01641.001生物体的遗传信息以DNA的形式存在于每个细胞的细胞核中，DNA被组织成染色体。这些染色体的确切结构随着细胞在细胞分裂周期的不同阶段的移动而变化。在被称为有丝分裂的阶段，细胞的DNA（先前已经复制）被共享到两个子细胞中，染色体变成紧密堆积的结构，可以很容易地在细胞质中移动。自世纪后期以来，人们已经知道，一层蛋白质，称为染色体周围层，覆盖在浓缩的染色体上。然而，实际上对这一层的作用一无所知。在有丝分裂开始后加入染色体周围层的第一个蛋白质之一被称为Ki-67。Ki-67仅在细胞活跃生长和分裂时在细胞核中发现，因此在研究这些过程的实验中被广泛用作标记物：例如，Ki-67用于检测身体组织中正常细胞中生长的肿瘤细胞，并测量旨在阻止肿瘤生长的药物的有效性。然而，人们对Ki-67的实际用途知之甚少。Booth等人现在揭示，当Ki-67不存在于细胞中时，染色体没有染色体周围层，或者充其量只有一小部分残留。这使得Booth等人也能够研究染色体周围层的作用。当染色体第一次进行有丝分裂时，没有染色体周围层，染色体的形状和行为没有变化。然而，新的细胞核比正常的小，它们的内容物排列不同。这导致子细胞合成蛋白质构建模块的能力出现问题，并导致子细胞试图进行下一次有丝分裂时自发细胞死亡率增加。需要进一步的研究来了解为什么会发生这种情况。DOI：http://dx.doi.org/10.7554/eLife.01641.002网站
When the nucleolus disassembles during open mitosis, many nucleolar proteins and RNAs associate with chromosomes, establishing a perichromosomal compartment coating the chromosome periphery. At present nothing is known about the function of this poorly characterised compartment. In this study, we report that the nucleolar protein Ki-67 is required for the assembly of the perichromosomal compartment in human cells. Ki-67 is a cell-cycle regulated protein phosphatase 1-binding protein that is involved in phospho-regulation of the nucleolar protein B23/nucleophosmin. Following siRNA depletion of Ki-67, NIFK, B23, nucleolin, and four novel chromosome periphery proteins all fail to associate with the periphery of human chromosomes. Correlative light and electron microscopy (CLEM) images suggest a near-complete loss of the entire perichromosomal compartment. Mitotic chromosome condensation and intrinsic structure appear normal in the absence of the perichromosomal compartment but significant differences in nucleolar reassembly and nuclear organisation are observed in post-mitotic cells. DOI: http://dx.doi.org/10.7554/eLife.01641.001 The genetic information of an organism is found in the nucleus of each cell in the form of DNA organised into chromosomes. The exact structure of those chromosomes changes as the cell moves through the different stages of the cell division cycle. During the stage called mitosis, where the DNA of a cell (which has previously been duplicated) is shared into two daughter cells, the chromosomes become tightly packed structures that can be readily moved through the cytoplasm. Since the late nineteenth century, it has been known that a layer of proteins, called the perichromosomal layer, coats the condensed chromosomes. However, virtually nothing was known about the role this layer performs. One of the first proteins to join the perichromosomal layer after mitosis begins is called Ki-67. This is only found in the cell nucleus when a cell is actively growing and dividing, and so is widely used as a marker in experiments investigating these processes: for example, Ki-67 is used to detect growing tumour cells amongst the normal cells in tissues of the body, and to measure the effectiveness of drugs designed to stop the growth of tumours. Again, however, little is known about what Ki-67 actually does. Booth et al. now reveal that when Ki-67 is not present in a cell, chromosomes do not have a perichromosomal layer—or at best, have a small remnant of one. This allowed Booth et al. to investigate the role of the perichromosomal layer as well. When the chromosomes first go through mitosis without a perichromosomal layer, no changes to the shape or the behaviour of the chromosomes are seen. However, the new nuclei are smaller than normal and their contents are arranged differently. This causes problems with the ability of daughter cells to synthesise protein building blocks and leads to an increased rate of spontaneous cell death when daughter cells try to undergo the next mitosis. Further research is needed to understand why this happens. DOI: http://dx.doi.org/10.7554/eLife.01641.002