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Nucleolus

About: Nucleolus is a research topic. Over the lifetime, 5873 publications have been published within this topic receiving 232435 citations. The topic is also known as: GO:0005730 & cell nucleolus.


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Book ChapterDOI
TL;DR: The evidence now available indicates that the fibrillar components of the nucleolus are the interphase counterpart of metaphase NORs, which is a useful tool for differentiating malignant from benign lesions in histological and cytological routine preparations.
Abstract: Publisher Summary This chapter discusses interphase nucleolar organizer regions (NORs) in cancer cells. In situ hybridization experiments have demonstrated that NORs contain the ribosomal genes. NORs are also characterized by the presence of proteins that are selectively stained by silver methods. During interphase, the nucleolus is the only site where both ribosomal genes and silver-stained proteins are located. The evidence now available indicates that the fibrillar components of the nucleolus are the interphase counterpart of metaphase NORs. Recently, interphase NORs have become an object of attention for pathologists because their distribution in the nucleolus has been shown to constitute a useful tool for differentiating, at the optical level, malignant from benign lesions in histological and cytological routine preparations. The chapter provides an overview of recent data about the structural-functional organization of interphase NORs, their importance in tumor pathology, and their relationship with the biological characteristics of cancer cells.

153 citations

Book ChapterDOI
TL;DR: Studies of electron micrographs of thin sections of nucleoli shows that the nucleolus contains two structural phases: one being essentially structureless, the other being a fine, highly coiled, stranded material.
Abstract: Publisher Summary This chapter discusses the structure and chemistry of nucleoli Nucleoli are generally described as homogeneous, spheroid, and intranuclear bodies that have an affinity for eosin in hematoxylin-eosin preparations but are basophilic in basic dye solutions However, the presence of vacuoles and inclusions of various kinds is widely recognized Studies of electron micrographs of thin sections of nucleoli shows that the nucleolus contains two structural phases: one being essentially structureless, the other being a fine, highly coiled, stranded material The electron micrographs reveal no indication of a limiting membrane around the nucleolus The nucleolus in plants is associated with a particular region of a given chromosome This region is characterized by its lack of staining with the Feulgen reaction for desoxyribonucleic acid (DNA) In the interphase, the nucleolus becomes hypertrophied during anabolic activity of the cell, and conversely becomes smaller during drastic catabolic states A number of experimental analyses exhibit that the nucleolus is composed of concentrated protein with variable amounts of ribonucleic acid (RNA)

152 citations

Journal ArticleDOI
TL;DR: The results prove the existence of heat-sensitive cellular functions in the nucleolus which deal with the DNA-dependent RNA synthesis and suggest that the granular RNP is reconverted to fibrillar RNP probably by simple unraveling.
Abstract: Striking nucleolar lesions occur in cultured cells after exposure to supranormal temperatures. These lesions appear at 42°C and consist of a loss of the granular ribonucleoprotein (RNP) component and intranucleolar chromatin, and a disappearance of the nucleolar reticulum. The material remaining in the morphologically homogeneous nucleolus is a large amount of closely packed fibrillar RNP. The lesions remain identical as temperature increases to 45°C. These alterations are reversible when the cells are returned to 37°C and are associated with the reappearance of an exaggerated amount of intranucleolar chromatin and granular RNP. High-resolution radioautography indicates that after thermic shock nucleolar RNA synthesis is inhibited whereas extranucleolar sites are preserved: it also suggests that the granular RNP is reconverted to fibrillar RNP probably by simple unraveling. The results prove the existence of heat-sensitive cellular functions in the nucleolus which deal with the DNA-dependent RNA synthesis. The precise site of action is assumed to involve hydrogen bonds, resulting in configurational changes in nucleolar RNP and affecting the stability of the DNA molecule. The subsequent events in nucleolar RNA synthesis are discussed in light of the morphologic and biochemical effects of actinomycin D on the nucleolus.

152 citations

Journal ArticleDOI
TL;DR: This work has identified the portions of ICP27 which can direct a cytoplasmic protein, pyruvate kinase (PK), to nuclei and demonstrated that I CP27 contains multiple nuclear localization signals (NLSs) that function with differing efficiencies.
Abstract: Previous work has shown that the herpes simplex virus type 1 (HSV-1) regulatory protein ICP27 localizes to the cell nucleus and that certain mutant ICP27 polypeptides localize preferentially in nucleoli. To map the signals in ICP27 which mediate its nuclear localization, we identified the portions of ICP27 which can direct a cytoplasmic protein, pyruvate kinase (PK), to nuclei. Our results demonstrate that ICP27 contains multiple nuclear localization signals (NLSs) that function with differing efficiencies. First, ICP27 possesses a strong NLS, mapping to residues 110 to 137, which bears similarity to the bipartite NLSs found in Xenopus laevis nucleoplasmin and other proteins. Second, ICP27 possesses one or more weak NLSs which map to a carboxyl-terminal portion of the protein between residues 140 and 512. Our PK-targeting experiments also demonstrate that ICP27 contains a relatively short sequence, mapping to residues 110 to 152, that can function as a nucleolar localization signal (NuLS). This signal includes ICP27's strong NLS as well as 15 contiguous residues which consist entirely of arginine and glycine. This latter sequence is very similar to an RGG box, a putative RNA-binding motif found in a number of cellular proteins which are involved in nuclear RNA processing. To confirm the results of the PK-targeting experiments, we mutated the ICP27 gene by deleting sequences encoding either the strong NLS or the RGG box. Deletion of the strong NLS (residues 109 to 138) resulted in an ICP27 molecule that was only partially defective for nuclear localization, while deletion of the RGG box (residues 139 to 153) resulted in a molecule that was nuclear localized but excluded from nucleoli. Recombinant HSV-1s bearing either of these deletions were unable to replicate efficiently in Vero cells, suggesting that ICP27's strong NLS and RGG box carry out important in vivo functions.

151 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023145
2022209
2021143
2020125
2019139
2018121