Karyoskeletal proteins and the organization of the amphibian oocyte nucleus

Benavente, Ricardo; Krohne, Georg; Schmidt-Zachmann, Marion S.; Hügle, Barbara; Franke, Werner W.

doi:10.1242/jcs.1984.supplement_1.11

Cited by 36 publications

(8 citation statements)

References 54 publications

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“…Jackson and Cook 1988;Cook 1991). The fibrillar components of the nucleolus (FC and DFC), or parts of them, may serve as supporting structures for DNA transcription and processing factors (see Benavente et al 1984 for review). The fibrillar components of the nucleolus (FC and DFC), or parts of them, may serve as supporting structures for DNA transcription and processing factors (see Benavente et al 1984 for review).…”

Section: Nucleolar Skeletonmentioning

confidence: 99%

The nucleolus

1993

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Nucleoli are the sites of biosynthesis of the ribosomal precursors. They contain may copies of the genes for the main rRNAs (18S- and 28 S-rRNA) in the form of tandemly arranged repeats at the chromosomal nucleolar organizer regions (NORs). They also contain the small rRNA (5S-rRNA) that is synthesized outside the nucleolus, specific nucleolar proteins, among them the factors and enzymes necessary for transcription and transcript processing, and the precursor units of the ribosomes. In man as in may vertebrate species, three main components of nucleoli, besides chromatin, can be detected: fibrillar centres (FC), dense fibrillar component (DCF), and granular component (GC). Within a nucleolus the FCs are in many cases situated in its central region. The DFc forms a network of strands surrounding the FCs, but may sometimes reach for out towards the periphery of the nucleolus. The GC is usually situated in the peripheral regions of the nucleolus. In cells with a low level of ribosomal biosynthesis the nucleoli are small, usually with a single FC and little surrounding DFC and GC ("ring-shaped nucleolus"). In active cells the DFC forms a large network enclosing several, sometimes up to hundreds of FCs, and the GC covers a large area in the periphery ("compact nucleoli"). In cells at the onset of a new stimulation, the DFC is very prominent whereas the FCs are few and small, and the GC is also not very extensive ("reticulate nucleoli"). In some special cell types that are very active other arrangements of the structural components are found. In Sertoli cells, for instance, only one nucleolus is found, or occasionally two, each with a single large FC and a distinct area of GC, both areas being engulfed by DFC intermingled with some peripheral GC. Immunocytological and in situ hybridization studies to localize the rRNA genes within the nucleolus have so far led to divergent results. Both fibrillar components, the FCs and the DFC, have been claimed as the most probable candidates. Transcription of rDNA and the subsequent early steps of ribosome biosynthesis are localized in the DFC, whereas later steps (mature rRNA, preribosomes) are localized in the GC. The FCs may also serve as sites for the preparation of the rDNA for transcription, and as a store for certain nucleolar proteins. During mitosis, parts of the nucleolar proteins remain at the NORs. A direct contact between the nucleolus and the nuclear envelope is frequently observed but is not dependent on nucleolar activity.(ABSTRACT TRUNCATED AT 400 WORDS)

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Section: Nucleolar Skeletonmentioning

confidence: 99%

The nucleolus

1993

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“…2). Furthermore, the inventory of nucleolar proteins is still growing and the function of even abundant nucleolar proteins such as N038jB23, a member of the nucleoplasmin family (29), nucleolinjC23 (32,33), and skeletal structural elements (34,35) is unknown.…”

Section: An Outline Of Nucleolus Organizationmentioning

confidence: 99%

Functional and dynamic aspects of the mammalian nucleolus

1990

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Nucleoli are the sites of ribosome biogenesis. Transcription of the ribosomal RNA genes as well as processing and initial packaging of their transcripts with ribosomal and non‐ribosomal proteins all occur within the nucleolus in an ordered manner and under defined topological conditions. Components of the nucleolus have been localized by immunocytochemistry and their functional aspects investigated by microinjection of antibodies directed against the enzyme responsible for rDNA transcription, RNA polymerase I. The role of nascent transcripts in postmitotic formation of nucleoli will be discussed.

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“…There is growing experimental evidence that nucleoli contain, in addition to pre-rRNA transcription units and preribosomal particles, abundant proteins that are thought to provide a structural support for the spatial arrangement of the rRNA genes and to play a role in the ordered translocation of preribosomal particles from their primary site of assembly to the nucleotar periphery (e.g., Franke et al, 1981;Moreno Diaz de la Espina et al, 1982;Schmidt-Zachmann et al, 1984;Benavente et al, 1984a; for review see Benavente et al, 1984b).…”

mentioning

confidence: 99%

Inhibition of nucleolar reformation after microinjection of antibodies to RNA polymerase I into mitotic cells.

Benavente

Rose

Reimer

et al. 1987

The Journal of Cell Biology

106

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Abstract, The formation of daughter nuclei and the reformation of nucleolar structures was studied after rnicroinjection of antibodies to RNA polymerase I into dividing cultured cells (PtK2). The fate of several nucleolar proteins representing the three main structural subcomponents of the nucleolus was examined by immunofluorescence and electron microscopy. The results show that the RNA polymerase I antibodies do not interfere with normal mitotic progression or the early steps of nucleologenesis, i.e., the aggregation of nucleolar material into prenucleolar bodies. However, they inhibit the telophasic coalescence of the prenucleolar bodies into the chromosomal nucleolar organizer regions, thus preventing the formation of new nucleoli. These prenucleolar bodies show a fibrillar organization that also compositionaUy resembles the dense fibrillar component of interphase nucleoli. We conclude that during normal nucleologenesis the dense fibrillar component forms from preformed entities around nucleolar organizer regions, and that this association seems to be dependent on the presence of an active form of RNA polymerase I.

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Karyoskeletal proteins and the organization of the amphibian oocyte nucleus

Cited by 36 publications

References 54 publications

The nucleolus

The nucleolus

Functional and dynamic aspects of the mammalian nucleolus

Inhibition of nucleolar reformation after microinjection of antibodies to RNA polymerase I into mitotic cells.

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