NUCLEOLUS
Updated 04-May-2020.
Mondo shtuff from around the internet, all about NUCLEOLUS!
The Thing Inside Your Cells That Might Determine How Long You Live: You may have forgotten about the nucleolus since you took biology class, but scientists think this structure inside every cell in your body may play an important role in aging.
The organization of ribosomal RNA processing correlates with the distribution of nucleolar snRNAs: We have analyzed the organization of pre-rRNA processing by confocal microscopy in pea root cell nucleoli using a variety of probes for fluorescence in situ hybridization and immunofluorescence. Our results show that transcript processing within the nucleolus is spatially highly organized. Probes to the 5′ external transcribed spacer (ETS) and first internal transcribed spacer (ITS1) showed that the excision of the ETS occurred in a sub-region of the dense fibrillar component (DFC), whereas the excision of ITS1 occurred in the surrounding region, broadly corresponding to the granular component. In situ labelling with probes to the snoRNAs U3 and U14, and immunofluorescence labelling with antibodies to fibrillarin and SSB1 showed a high degree of coincidence with the ETS pattern, confirming that ETS cleavage and 18 S rRNA production occur in the DFC. ETS, U14, fibrillarin and SSB1 showed a fine substructure within the DFC comprising closely packed small foci, whereas U3 appeared more diffuse throughout the DFC. A third snoRNA, 7–2/MRP, was localised to the region surrounding the ETS, in agreement with its suggested role in ITS1 cleavage. All three snoRNAs were also frequently observed in numerous small foci in the nucleolar vacuoles, but none was detectable in coiled bodies. Antibodies to fibrillarin and SSB1 labelled coiled bodies strongly, though neither protein was detected in the nucleolar vacuoles. During mitosis, all the components analyzed, including pre-rRNA, were dispersed through the cell at metaphase, then became concentrated around the periphery of all the chromosomes at anaphase, before being localized to the developing nucleoli at late telophase. Pre-rRNA (ETS and ITS1 probes), U3 and U14 were also concentrated into small bodies, presumed to be pre-nucleolar bodies at anaphase.
My botty best at summarizing from Wikipedia: the nucleolus is best known as the site of ribosome biogenesis . nucleoli are made of proteins, DNA and RNA and form around specific chromosomal regions . malfunction of nucle a study of nucleoli by John Gurdon and Donald Brown in the African clawed frog Xenopus laevis generated increasing interest in the function and detailed structure of the nucleolus . in Transcription of the rDNA occurs in the FC . the protein fibrillarin is important in rRNA processing . it has been proposed that this particular organization is only observed in higher eukaryotes a clear area in the center of the structure referred to as a nucleolar vacuole . nucleoli of various plant species have been shown to have very high concentrations of iron . a diploid rRNA genes are transcribed as a single unit within the nucleolus by RNA polymerase I . several pol I-associated factors and DNA-specific trans-acting factors are required . in in eukaryotes, the RNA-modifying enzymes are brought to their respective recognition sites by interaction with guide RNAs, which bind these specific sequences . the 18S RNA, 5.8S and in yeast, the 5S rDNA sequence is localized in the intergenic spacer . it is transcribed in the nucleolus by RNA pol . in higher eukaryotes and plants association and maturation of rRNA and r-proteins result in the formation of the 40S (small) and 60S (large) subunits of the complete ribosome . these are exported through the nuclear long noncoding RNAs originating from intergenic regions of the nucleolus are responsible for this phenomenon .