The Nucleolus and Viral Infection

The nucleolus is a subnuclear structure of eukaryocytes. It was thought that nucleolus only participates in the biogenesis and processing of rRNA. However, more and more evidence shows that it has many other functions, such as tRNA precursor processing, stress sensing and it is also involved in gene silencing, senescence and cell cycle regulation. Here, we summarize the recent understandings about the nucleolar functions, the regulation of nucleolar localization of proteins and the role that the nucleolus p...     

核仁和核仁蛋白

核仁是位于细胞核内的非膜结构。电子显微镜下的核仁从形态上可以分为三层结构包括纤维中心区(FC)、高密度纤维区(DFC)和颗粒区(GC)。核仁内的蛋白有核糖体蛋白和非核糖体蛋白两种。利用蛋白质组学方法已经鉴定了350多种核仁蛋白,其中包括80多种核糖体蛋白。核仁是核糖体合成的场所,核仁中的非核糖体蛋白对核糖体的生物合成起关键调控作用。核仁不仅是细胞内通讯和核糖体：RNA加工的中心,而且在细胞周期、细胞增殖和衰老中起重要调控作用;核仁也是tRNA、mRNA和其它类型小分子RNA加工的场所。因此核仁是一个多功能的细胞生命活动中心。     

The Nucleolus in the Induced Amitosis

Nucleolar cycles were related to mitotic and amitotic phasesin meristematic cells of Allium cepa L. roots growing in controlconditions and in others where amitosis was induced by a 6-htreatment with ethidium bromide. The induced amitosis in these cells was followed by an unbalanceddistribution of chromosomal material between the two independentdaughter cells resulting from it. The first discrepancy between mitosis and amitosis was foundat the level of prophase nucleolar disorganization, which wasgreatly modified. The nucleolar cycle was permanently stoppedin amitosis even when recovery from treatment was allowed. Thekinetics of amitosis appearance in the meristem suggest a decisionpoint located round about mid-prophase. This decision pointseems to involve nucleolar function in prophase. These observationsconfirm the fact that prophase is one of the decisive stagesin the differentiation of a cell.     

核仁的蛋白质组学

核仁是胞核内高度紧密的结构,参与转录、剪接、核糖体合成等重要生命过程,并与细胞分裂、衰老有关。1963年虽已从哺乳动物肝脏提纯核仁,并鉴定了所含的一些蛋白质,但还有不少核仁蛋白质迄今尚未阐明。2002年英国、丹麦的两实验室首次完成了核仁的蛋白质组学分析。本文就近年报道有关核仁蛋白质组的分离和检测、检出的271种核仁蛋白质的分类,蛋白质在胞核内迁移以及核仁蛋白质组学检测技术的问题和发展前景等方面作一简介。     

Nucleolus organizer region--centromere translocation

A karyotype 45,XX,-13,-15,+psudic (13;15)(p12.9;11.200) was observed in a young woman after two spontaneous miscarriages. After R-, C-, and NOR - banding - the rearranged element was shown to include: the long arm, the active centromere, and the NOR of chromosome 13, followed by the inactivated centromere, and the long arm of chromosome 15.     

Nucleolus in the Spotlight

The recent contributions on chromatid segregation at the metaphase/anaphase transition demonstrate two distinct pathways in budding yeast. While segregation of most of the genome is a direct consequence of cohesin cleavage by separase, rDNA segregation requires a novel pathway involving Cdc14 phosphatase activation. This activation induces targeting of condensin to rDNA which in association with Aurora B kinase modulates rDNA compaction during anaphase. The resolution of rDNA sequences occurs after this step.     

The Nucleolus and Parachromatin of the Ascites Tumor Cell

1. A method is described for distinguishing the ribonucleoproteins of the nucleolus and parachromatin of ascitic tumor cells of the mouse. 2. In these cells the transfer of ribonucleoprotein from the nucleus to the cytoplasm can occur in two ways. (a) At the end of prophase the nucleolus separates from the chromosomes and nucleolar fragments are released into the cytoplasm. (b) During prophase the parachromatin is aggregated to form parachromatin bodies which are discharged into the cytoplasm, where they can be detected during metaphase, anaphase, and telophase. 3. A metachromatic form of RNA is demonstrable, and may be synthesized, in close relation to the chromosomes during prophase, metaphase, and anaphase. During telophase the distribution of metachromatic RNA changes, the chromatin loses its metachromasia, and intranuclear metachromatic parachromatin becomes evident.     

Über den Nucleolus der Nervenzelle

Zusammenfassung Bei supravitaler Fixierung und Anwendung besonderer Färbetechnik lassen sich in zahlreichen Nucleoli der Nervenzelle bei einer Reihe von Säugetieren vielfältige Strukturen erkennen, welche auch mit der Phasenkontrastoptik nachweisbar sind. Es läßt sich nachweisen, daß aus diesen Strukturen, die als Innenkörperchen bezeichnet werden. die Vakuolen entstehen, welche auf Grund des morphologischen Substrates als ein physiologisches Produkt des Nucleolus anzusehen sind. Damit erfahren die Vorstellungen von Körner (1937), C. und O. Vogt 1946, 1947) u. a. eine weitere Stütze.Die Untersuchungen wurden durch die Unterstützung der Deutschen Forschungsgemeinschaft ermöglicht.     

The Effect of Ph on Silver Staining of Nucleolus Organizer Regions

The effect of pH on silver staining of the nucleolus organizer regions (NORs) of human chromosomes has been investigated between pH 6.5 and 12.0. Nonvolatile mixtures of ethanolamine and ethanolammonium nitrate replaced the ammonia of standard procedures. The optimal NOR staining obtained at pH 3.5 by the silver staining procedure of Howell and Black served as a standard; this procedure stained all ten NORs in 90% of mitoses. Similar NOR staining was found in 75% of mitoses stained at pH 11.7 or 11.8, but only in 10-15% of mitoses stained between pH 11.6 and 10.0. Between pH 10.0 and 9.0 NOR staining was incomplete, and between pH 8.5 and 6.5 there was no NOR staining.     

Nucleolus: the fascinating nuclear body

Nucleoli are the prominent contrasted structures of the cell nucleus. In the nucleolus, ribosomal RNAs are synthesized, processed and assembled with ribosomal proteins. RNA polymerase I synthesizes the ribosomal RNAs and this activity is cell cycle regulated. The nucleolus reveals the functional organization of the nucleus in which the compartmentation of the different steps of ribosome biogenesis is observed whereas the nucleolar machineries are in permanent exchange with the nucleoplasm and other nuclear bodies. After mitosis, nucleolar assembly is a time and space regulated process controlled by the cell cycle. In addition, by generating a large volume in the nucleus with apparently no RNA polymerase II activity, the nucleolus creates a domain of retention/sequestration of molecules normally active outside the nucleolus. Viruses interact with the nucleolus and recruit nucleolar proteins to facilitate virus replication. The nucleolus is also a sensor of stress due to the redistribution of the ribosomal proteins in the nucleoplasm by nucleolus disruption. The nucleolus plays several crucial functions in the nucleus: in addition to its function as ribosome factory of the cells it is a multifunctional nuclear domain, and nucleolar activity is linked with several pathologies. Perspectives on the evolution of this research area are proposed.     

胚胎早期发育过程中核仁前体的研究进展

核仁前体存在于卵母细胞及早期胚胎中,由于核仁前体在卵母细胞中的含量较少且结构致密,目前,只有少数核仁前体组分得到了鉴定.核仁前体结构的完整组成尚未被详细解析,明确核仁前体在胚胎早期发育过程中发挥的作用及其机制尚存挑战.早期的观点认为:核仁前体虽不具备加工rRNA及生成核糖体的功能,但该结构为纤维颗粒状核仁的生成提供了物质基础,从而使发育后期胚胎重获核糖体生成能力.近期,这一观点逐步得到了修正.基于显微操作技术的核仁前体转移实验证实:母源核仁前体在胚胎早期发育过程中发挥关键作用,且发挥作用的时间窗口限定在受精至原核期之间.核仁前体可参与染色质重塑过程并维持着丝粒稳定,进而影响胚胎早期发育.本文主要综述了核仁前体的结构功能特点及发挥作用的潜在机制,从核仁前体的角度为拯救早期胚胎的发育潜能提供新思路.