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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: Repression of an essential nucleolar small nuclear RNA (snRNA) gene of Saccharomyces cerevisiae was shown to result in impaired production of 18S rRNA, and a common U14 designation is proposed for the structurally related yeast snRNA and 4.5S hybRNAs from amphibians and mammals.
Abstract: Repression of an essential nucleolar small nuclear RNA (snRNA) gene of Saccharomyces cerevisiae was shown to result in impaired production of 18S rRNA. The effect, observed for an snRNA species of 128 nucleotides (snR128), was evident within one generation after the onset of SNR128 gene repression and correlated well with depletion of the snRNA. The steady-state mass ratio of 18S RNA to 25S RNA decreased eightfold over the course of the analysis. Results from pulse-chase assays revealed the basis of the imbalance to be underaccumulation of 18S RNA and its 20S precursor. This effect appears to result from impairment of processing of the 35S rRNA transcript at sites that define the 20S species coupled with rapid turnover of unstable intermediates. Possible bases for the effects observed are discussed. A common U14 designation is proposed for the structurally related yeast snRNA and 4.5S hybRNAs from amphibians and mammals.

238 citations

Journal ArticleDOI
TL;DR: Two major silver staining proteins were found which were identified as (molecular weight × 10 −3 /pI) proteins C23 and B23 which are the major acidic proteins in Novikoff hepatoma nucleoli.

236 citations

Journal ArticleDOI
TL;DR: It is shown that yeast U3 can be cross‐linked to 35S pre‐rRNA both in deproteinized extracts and in living cells, and it is proposed that this site may be evolutionarily conserved to direct the assembly of a pre-rRNA processing complex required for the cleavages that generate 18S rRNA.
Abstract: It has long been known that U3 can be isolated hydrogen bonded to pre-ribosomal RNAs, but the sites of interaction are poorly characterized. Here we show that yeast U3 can be cross-linked to 35S pre-rRNA both in deproteinized extracts and in living cells. The sites of cross-linking were localized to the 5' external transcribed spacer (ETS) and then identified at the nucleotide level. Two regions of U3 near the 5' end are cross-linked to pre-rRNA in vivo and in vitro; the evolutionarily conserved box A region and a 10 nucleotide (nt) sequence with perfect complementarity to an ETS sequence. Two in vivo cross-links are detected in the ETS, at +470, within the region complementary to U3, and at +655, close to the cleavage site at the 5' end of 18S rRNA. A tagged rDNA construct was used to follow the effects of mutations in the ETS in vivo. A small deletion around the +470 cross-linking site in the ETS prevents the synthesis of 18S rRNA. This region is homologous to the site of vertebrate ETS cleavage. We propose that this site may be evolutionarily conserved to direct the assembly of a pre-rRNA processing complex required for the cleavages that generate 18S rRNA.

234 citations

Journal ArticleDOI
TL;DR: A function for noncoding RNA (ncRNA) is reported in the regulation of protein dynamics of key cellular factors, including VHL, Hsp70 and MDM2/PML, and proposed a model whereby protein immobilization by ncRNA is a posttranslational regulatory mechanism.

232 citations

Journal ArticleDOI
TL;DR: Findings reinforce the growing realization that nucleoli orchestrate the chain of events the celluses to properly respond to stress signals, and show stress-induced release of nucleolar proteins to carry out other regulatory functions.
Abstract: All organisms sense and respond to conditions that stress their homeostatic mechanisms. Here we review current studies showing that the nucleolus, long regarded as a mere ribosome producing factory, plays a key role in monitoring and responding to cellular stress. After exposure to extra- or intracellular stress, cells rapidly down-regulate the synthesis of ribosomal RNA. Impairment of nucleolar function in response to stress is accompanied by perturbation of nucleolar structure, cell cycle arrest and stabilization of p53. The nucleolar target for down-regulation of rDNA transcription is TIF-IA, an essential transcription factor that modulates the activity of RNA polymerase I (Pol I). Upon stress, TIF-IA is phosphorylated by c-Jun N-terminal kinase 2 (JNK2). Phosphorylation prevents TIF-IA from interaction with Pol I, thereby impairing transcription complex formation and rRNA synthesis. Furthermore, stress-induced inactivation of TIF-IA is accompanied by translocation of TIF-IA from the nucleolus to the nucleoplasm. These findings, together with other data showing stress-induced release of nucleolar proteins to carry out other regulatory functions, reinforce the growing realization that nucleoli orchestrate the chain of events the cell uses to properly respond to stress signals.

232 citations


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