Journal ArticleDOI
Fine structural ribonucleoprotein components of the cell nucleus visualized after spreading and high resolution autoradiography.
Stanislav Fakan,Marie E. Hughes +1 more
TLDR
The present observations suggest that the nucleolar dense fibrillar component, shown previously in ultrathin sections of [3H]uridine-labelled intact cells as carrying rapidly labelled pre-rRNA, in fact consists of highly compacted transcribing ribosomal genes.Abstract:
The fine structure of the nuclear components was studied following mild lysis of mouse or Drosophila tissue culture cells and spreading of nuclear material. Particular attention was paid to nuclear ribonucleoprotein (RNP) constituents, which were analysed by high resolution autoradiography after [3H]uridine pulse labelling of cells. Comparison with the labelling kinetics of various in situ nuclear RNP constituents described previously suggests strong similarities between in situ constituents and structures observed within spread nuclear components. The present observations suggest that the nucleolar dense fibrillar component, shown previously in ultrathin sections of [3H]uridine-labelled intact cells as carrying rapidly labelled pre-rRNA, in fact consists of highly compacted transcribing ribosomal genes. The growing RNP fibrils appearing in transcription complexes of extranucleolar active genes and the in situ observed perichromatin fibrils also show the same labelling properties. This confirms that the two structures indeed represent the same nucleoplasmic constituents. As for the nuclear structures involved in post-transcriptional events, our observations demonstrate the occurrence of a rapidly labelled RNP fibro-granular network. Its granular elements correspond, in size and perichromatin location, to the perichromatin granules seen in the situ preparations and suggest similarities between the two constituents. The results are discussed in the light of other data providing information on the role of various nuclear structural constituents.read more
Citations
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Journal ArticleDOI
Perichromatin fibrils are in situ forms of nascent transcripts
TL;DR: Current evidence strongly supports the idea that perichromatin fibrils are the in situ form of hnRNA transcripts and sites of pre-mRNA processing steps such as splicing and polyadenylation.
Book ChapterDOI
The Nuclear Matrix: Past and Present
TL;DR: The studies on rat osteosarcoma cells suggested that these tumor cells are expressing matrix proteins normally expressed only at earlier developmental stages in the osteoblast lineage, and this chapter describes the structure and function of the nuclear matrix.
Journal ArticleDOI
The nucleolus and transcription of ribosomal genes.
TL;DR: The recent results on the regulation of rRNA synthesis in relation to the functional organization of the nucleolus are discussed, and an emphasis on the situation encountered in mammalian somatic cells is put on.
Book ChapterDOI
The architectural organization of nuclear metabolism
TL;DR: Many of the intermediates and the regulatory and catalytic factors of nucleic acid metabolism are retained in nuclear matrix preparations, suggesting that nucleic Acid synthesis and processing are structure-bound processes in cells.
Journal ArticleDOI
Nucleolar organization of HeLa cells as studied by in situ hybridization.
TL;DR: Observations are consistent with the view that DFCs contain elongating and 47S–45S precursor rRNA molecules whereas the subsequent various rRNA processing intermediates are mainly located within the GC.
References
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Journal ArticleDOI
Visualization of Nucleolar Genes
O. L. Miller,Barbara R. Beatty +1 more
TL;DR: The presence of extrachromosomal nucleoli in amphibian oocytes has permitted isolation and electron microscopic observation of the genes coding for ribosomal RNA precursor molecules.
Journal ArticleDOI
Fine structural organization of the interphase nucleus in some mammalian cells.
Ariane Monneron,W. Bernhard +1 more
TL;DR: In the interphase nucleus, the distribution and fine structure of various components known to contain or should carry RNP have been investigated on ultrathin sections by means of a new preferential staining method and the use of various enzymatic and chemical extraction procedures.
Book ChapterDOI
The nucleolar structure.
TL;DR: The nucleusolus is organized at the nucleolus-organizing region of the chromosomes, which are generally visible as secondary constriction regions in metaphase chromosomes, and the chromatin within the constriction region is lost at interphase inside the nucleoli.
Book ChapterDOI
The Ultrastructural Visualization of Nucleolar and Extranucleolar RNA Synthesis and Distribution
TL;DR: It is concluded that the layer of chromatin decondensing on the periphery of dense chromatin areas represents the most active chromatin fraction in the nucleus.
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Fine structural organization of the interphase nucleus in some mammalian cells.
Ariane Monneron,W. Bernhard +1 more