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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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Journal ArticleDOI
TL;DR: A brief report on the nucleolus and diseases is proposed as well as of nucleolar functions different from ribosome biogenesis, which is an intriguing observation since the role of these pre-rRNAs is presently unknown.
Abstract: Nucleoli are the prominent contrasted structures of the cell nucleus. In the nucleolus, ribosomal RNAs (rRNAs) are synthesized, processed and assembled with ribosomal proteins. The size and organization of the nucleolus are directly related to ribosome production. The organization of the nucleolus reveals the functional compartmentation of the nucleolar machineries that depends on nucleolar activity. When this activity is blocked, disrupted or impossible, the nucleolar proteins have the capacity to interact independently of the processing activity. In addition, nucleoli are dynamic structures in which nucleolar proteins rapidly associate and dissociate with nucleolar components in continuous exchanges with the nucleoplasm. At the time of nucleolar assembly, the processing machineries are recruited in a regulated manner in time and space, controlled by different kinases and form intermediate structures, the prenucleolar bodies. The participation of stable pre-rRNAs in nucleolar assembly was demonstrated after mitosis and during development but this is an intriguing observation since the role of these pre-rRNAs is presently unknown. A brief report on the nucleolus and diseases is proposed as well as of nucleolar functions different from ribosome biogenesis.

143 citations

Journal ArticleDOI
TL;DR: The identification of different factors on all regulatory levels, such as transcription factors, histone modifications, chromatin proteins, DNA sequences and non-coding RNAs, suggests the involvement of multiple distinct tethering pathways.

143 citations

Journal ArticleDOI
TL;DR: The accumulation of POD-associated proteins and proteasomes in the nucleoli of MG132-treated cells indicates that these proteins may target theucleoli under normal conditions and that the nucleolus may have a function in the regulation of proteasomal protein degradation.
Abstract: Several recent findings have indicated that the promyelocytic leukemia gene product (PML) oncogenic domains (PODs) are involved in proteasome-mediated degradation of ubiquitinated proteins We wanted to examine the intracellular distribution of PML protein in the presence of a proteasome inhibitor We used high-resolution microscopy to study the distribution of PML protein and other POD-associated proteins along with the proteasomes themselves under normal conditions and in cells treated with the proteasome inhibitor, MG132 Inhibition of the proteasomes in MCF-7, HeLa, and IB-4 cell lines resulted in a radical redistribution of the POD-associated proteins PML, Sp100, and SUMO-1 After 6–10 h of MG132 treatment, PML, Sp100, and SUMO-1 were no longer detectable in the PODs and accumulated mainly in the nucleolus Moreover, MG132 treatment changed the cellular distribution of the proteasomes Interestingly, this included the accumulation in euchromatin areas of the nucleus and within the nucleoli Several non-POD-associated proteins did not change their cellular distribution under the same conditions The accumulation of POD-associated proteins and proteasomes in the nucleoli of MG132-treated cells indicates that these proteins may target the nucleoli under normal conditions and that the nucleolus may have a function in the regulation of proteasomal protein degradation

143 citations

Journal ArticleDOI
TL;DR: Amongst the axolotl9s haploid complement of fourteen mitotic chromosomes, one of the four largest, with a greater arm asymmetry than the other three, shows a nucleolar constriction subterminally in its shorter arm.
Abstract: Amongst the axolotl9s haploid complement of fourteen mitotic chromosomes, one of the four largest, with a greater arm asymmetry than the other three, shows a nucleolar constriction subterminally in its shorter arm. Low-temperature treatment causes further secondary constrictions to appear; these constrictions enable most of the mitotic chromosomes to be identified; the constrictions occur at similar sites in the chromosomes of tail-fin epithelial cells, hepatocytes, and brain cells. Homology between the mitotic and oocyte (lampbrush) nucleolar organizers has been established, and thus the several hundred free nucleoli in oocytes are genetically related to the two nucleoli of diploid somatic interphases. During oocyte development the free nucleoli transform from solid structures to rings and back to solid structures again without detectable increase in number. During the contraction and aggregation of the lampbrush chromosomes within the oocyte nucleus as maturity approaches, in most axolotls the free ring-shaped nucleoli become stretched between the nuclear periphery and central chromosome group, and take on a characteristic beaded appearance. These transformations of the free nucleoli are largely paralleled by forms which nucleoli attached subterminally to the shorter arm of lampbrush chromosome III concurrently assume. The question as to whether fully developed nucleoli detach from the organizer loci and add to the population of free nucleoli in oocytes remains undecided. It may well be that virtually all the DNA-generators of free nucleoli detach from the organizer loci before starting to carry out nucleolar functions, and before there is any significant accumulation of protein and RNA around them. If so, the variability in quantity of attached nucleolar material may not reflect different states in a nucleolar synthesis and detachment cycle, but rather variation in the number of nucleolar DNA Anlagen which happen to remain attached to the organizer loci after the synthesis and detachment of the great majority of the Anlagen has ceased. In occasional oocytes the only chromosomal continuity maintained across the organizer locus consists of a nucleolar ‘double bridge’; this indicates that the genetically persistent (i.e. chromosomal) organizer DNA bears the same structural relationship to neighbouring parts of a lampbrush chromosome as any other chromomere with its attendant pair of lateral loops. The lampbrush chromosomes of the axolotl have been provisionally mapped. The centromeres are represented by short portions of chromosome axis without lateral loops, and there are two spheres close to the centromeres of both chromosome VI and chromosome XIII. Other recognition characters are inconspicuous or not very reliable, and features of the lampbrush chromosomes related to the low-temperature induced secondary constrictions of mitotic chromosomes have not been identified.

142 citations

Journal ArticleDOI
TL;DR: Protein C23 was found in ‘fibrillar centers’ (nucleolonemas) in nucleoli and demonstrated to be present on the nucleolus organizer regions (NORs) of metaphase chromosomes in Novikoff hepatoma nucleoli.

142 citations


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