Topic
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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TL;DR: A model in which Bop1 serves as an essential factor in ribosome formation that coordinates processing of the spacer regions in pre-rRNA is proposed, which demonstrates that Bop 1 is required for proper processing at four distinct sites located within the internal transcribed spacers ITS1 and ITS2 and the 3′ external spacer.
104 citations
TL;DR: It is postulate that the altered structure of the 45-S RNA does not permit this conversion of rRNA to tRNA, and synthesis of tRNA is not inhibited by toyocamycin, as shown by the ratio of methylation to nucleoside incorporation.
103 citations
TL;DR: It is concluded that Cdc14 is released from the nucleolus at the onset of anaphase in a CDC5-dependent manner and that MEN factors possibly regulate CDC14 release from the SPB.
103 citations
TL;DR: Glenodinium foliaceum Stein (Pyrrophyta) has a single mesocaryotic nucleus which contains numerous typically dinoflagellate chromosomes and one or more nucleoli with a structure similar to that of nucleoli in higher organisms.
Abstract: Glenodinium foliaceum Stein (Pyrrophyta) has a single mesocaryotic nucleus which contains numerous typically dinoflagellate chromosomes and one or more nucleoli with a structure similar to that of nucleoli in higher organisms. In addition this organism possesses another nucleus-like organelle which is here termed the eucaryotic nucleus. This is a polymorphic body which varies in shape from ovoid to a branched filamentous form. As with the mesocaryotic nucleus it is surrounded by a perforated envelope. The organelle contains granular material and usually several nucleoli which again appear to have the typical form of nucleoli. No other dinoflagellate is known in which two nuclei of differing types are found. The function and significance of the presence of the two nuclei is discussed.
103 citations
TL;DR: It is concluded that an abundance of protein-bound sulfhydryl and disulfide groups occur at nucleolar organizing regions with active genes, suggestive of a great flexibility of protein(s) by transition of sulfHydryl groups to disulfides bridges and vice versa at these highly active regions of the genome.
Abstract: Silver stainability of the chromosomal nucleolus organizing regions that contain the structural genes for ribosomal RNA can be abolished by proteolytic and oxidative treatments. Histone extraction has no effect. This indicates that reducing groups of non-histone chromosomal proteins are responsible for silver staining. Treatment with fluorescent sulfhydryl and disulfide specific reagents followed by silver staining demonstrates coincidence of silver dots and brightly fluorescent spots at the short arms of human acrocentric chromosomes where ribosomal RNA-genes are located. After treatment with cupric sulfite reagent in the presence of urea fluorescence and silver staining was no longer possible. Silver staining has been reported to be associated with ribosomal RNA-gene activity. Acrocentric chromosomes that are negative in silver staining also lack the brightly fluorescent spots. Therefore, we conclude that an abundance of protein-bound sulfhydryl and disulfide groups occur at nucleolar organizing regions with active genes. Differentially fluorescing spots could not be observed after staining with fluorescamine. So, either the sulfhydryl reagents used in this study are much more sensitive than fluorescamine to study protein distributions in cytological preparations, or our observations point to a local accumulation of some specific protein(s) rich in sulfhydryls. The presence of many sulfhydryl and disulfide groups at the nucleolus organizing regions seems suggestive of a great flexibility of protein(s) by transition of sulfhydryl groups to disulfide bridges and vice versa at these highly active regions of the genome.
103 citations