Repopulation of Postmitotic Nucleoli by Preformed Rna

Phillips, David M.; Phillips, Stephanie Gordon

doi:10.1083/jcb.58.1.54

Cited by 23 publications

(5 citation statements)

References 19 publications

(29 reference statements)

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“…This dissociation and reassembly cycle shows that the nucleolar form of protein Sl-containing ma-terial is different from cytoplasmic ribosomes as it is selectively recollected into the daughter nuclei, indicative of the existence of a sorting process separating the nucleolar S I complexes from cytoplasmic ribosomes. Our immunocytochemical observations are compatible with the conclusions of Fan and Penman (76), based on biochemical studies of nucleolar RNA, that ribosomal precursor material released from disintegrated nucleoli persists during mitosis and repopulates the postmitotic nucleolus (77,78). The ultrastructural organization of the small nucleolus-derived granules and the chromosome-associated S I material in mitotic cells is currently being studied in our laboratory by immunoelectron microscopy.…”

Section: Distribution Of Ribosomal Protein 51 During Mitosissupporting

confidence: 88%

Localization of ribosomal protein S1 in the granular component of the interphase nucleolus and its distribution during mitosis.

Hügle¹,

Hazan²,

Scheer³

et al. 1985

The Journal of Cell Biology

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Using antibodies to various nucleolar and ribosomal proteins, we define, by immunolocalization in situ, the distribution of nucleolar proteins in the different morphological nucleolar subcompartments. In the present study we describe the nucleolar localization of a specific ribosomal protein ($1) by immunofluorescence and immunoelectron microscopy using a monoclonal antibody (RS1-105). In immunoblotting experiments, this antibody reacts specifically with the largest and most acidic protein of the small ribosomal subunit ($1) and shows wide interspecies cross-reactivity from amphibia to man. Beside its localization in cytoplasmic ribosomes, this protein is found to be specifically localized in the granular component of the nucleolus and in distinct granular aggregates scattered over the nucleoplasm. This indicates that ribosomal protein $1, in contrast to reports on other ribosomal proteins, is not bound to nascent pre-rRNA transcripts but attaches to preribosomes at later stages of rRNA processing and maturation. This protein is not detected in the residual nucleolar structures of cells inactive in rRNA synthesis such as amphibian and avian erythrocytes. During mitosis, the nucleolar material containing ribosomal protein $1 undergoes a remarkable transition and shows a distribution distinct from that of several other nucleolar proteins. In prophase, the nucleolus disintegrates and protein $1 appears in numerous small grariules scattered throughout the prophase nucleus. During metaphase and anaphase, a considerable amount of this protein is found in association with the surfaces of all chromosomes and finely dispersed in the cell plasm. In telophase, protein Sl-containing material reaccumulates in granular particles in the nucleoplasm of the newly formed nuclei and, finally, in the re-forming nucleoli. These observations indicate that the nucleolus-derived particles containing ribosomal protein $1 are different from cytoplasmic ribosomes and, in the living cell, are selectively recollected after mitosis into the newly formed nuclei and translocated into a specific nucleolar subcompartment, i.e., the granular component. The nucleolar location of ribosomal protein $1 and its rearrangement during mitosis is discussed in relation to the distribution of other nucleolar proteins.The current concept of the functional organization of the nucleolus is primarily based on electron microscopy and some information at the nucleic acid level. Thus, the nucleolus is defined as a cluster of transcriptionally active rRNA genes that is associated with structures representing a stockpile of ribosomal precursor particles at various stages of processing and maturation (for reviews see references 1-3). By electron microscopy, three morphologically distinct nucleolar components have been distinguished (for reviews see references 4-6): the fibrillar center(s), the dense fibrillar component, and the granular component. Different functions have been assigned to these nucleolar substructures. Recently, RNA polymerase I, the enzyme ...

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Section: Distribution Of Ribosomal Protein 51 During Mitosissupporting

confidence: 88%

Localization of ribosomal protein S1 in the granular component of the interphase nucleolus and its distribution during mitosis.

Hügle¹,

Hazan²,

Scheer³

et al. 1985

The Journal of Cell Biology

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“…Recent work by Zatsepina et al (1997) also showed that hypotonically induced nucleolar bodies structually similar to the NDF can reassemble into nucleoli after cells are returned to isotonic conditions during interphase. This supports the idea that nucleoli may be reassembled from previously existing nucleolar components as suggested by Phillips and Phillips (1973). A study by Medina et al (1995) indicates that RNAs radiolabeled in G 2 phase accumulate in nucleoli in telophase and early G 1 phase.…”

Section: Discussionsupporting

confidence: 69%

Partially Processed pre-rRNA Is Preserved in Association with Processing Components in Nucleolus-derived Foci during Mitosis

Dundr

Olson

1998

MBoC

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Previous studies showed that components implicated in pre-rRNA processing, including U3 small nucleolar (sno)RNA, fibrillarin, nucleolin, and proteins B23 and p52, accumulate in perichromosomal regions and in numerous mitotic cytoplasmic particles, termed nucleolus-derived foci (NDF) between early anaphase and late telophase. The latter structures were analyzed for the presence of pre-rRNA by fluorescence in situ hybridization using probes for segments of pre-rRNA with known half-lives. The NDF did not contain the short-lived 5Ј-external transcribed spacer (ETS) leader segment upstream from the primary processing site in 47S pre-rRNA. However, the NDF contained sequences from the 5Ј-ETS core, 18S, internal transcribed spacer 1 (ITS1), and 28S segments and also had detectable, but significantly reduced, levels of the 3Ј-ETS sequence. Northern analyses showed that in mitotic cells, the latter sequences were present predominantly in 45S-46S pre-rRNAs, indicating that high-molecular weight processing intermediates are preserved during mitosis. Two additional essential processing components were also found in the NDF: U8 snoRNA and hPop1 (a protein component of RNase MRP and RNase P). Thus, the NDF appear to be large complexes containing partially processed pre-rRNA associated with processing components in which processing has been significantly suppressed. The NDF may facilitate coordinated assembly of postmitotic nucleoli. INTRODUCTIONThe nucleolus is a prominent membraneless subnuclear compartment assembled around clusters of tandemly repeated rDNA genes from which prerRNA is transcribed and subsequently folded, processed, modified, and assembled into small and large ribosomal subunits (Scheer et al., 1993;Shaw and Jordan, 1995;Maden and Hughes, 1997). A remarkable aspect of the cell cycle is the disintegration of the nucleolus during mitosis and its reassembly as the daughter cells proceed toward G 1 phase. A pivotal event in this process is the repression of RNA polymerase (pol) I-driven pre-rRNA synthesis between prophase and telophase (Prescott and Bender, 1962). At the same time, nucleolar components disperse to various subcellular locations as the maternal nucleoli diassemble (Goessens, 1984).A comprehensive understanding of the locations and fates of nucleolar components during mitosis is slowly emerging (Scheer et al., 1993;Hernandez-Verdun and Gautier, 1994). For example, much of the RNA pol I transcription machinery and DNA topoisomerase I remain associated with the nucleolus organizer regions (NORs) 1 of chromosomes between nucleolar disassembly in late prophase and reassembly in telophase (Scheer et al., 1993; Weisenberger and * Corresponding author. 1 Abbrevations used: DFC, dense fibrillar component; ETS, external transcribed spacer; GC, granular component; ITS, internal transcribed spacer; NDF, nucleolus-derived foci; NOR, nucleolus organizer region; PNB, prenucleolar body; pol, polymerase; snoRNA, small nucleolar RNA; sno-RNP, small nucleolar ribonucleoprotein.© 1998 by The American Society for Ce...

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“…16 in Fawcett [10] and the discussion, p. 440, in Busch and Smetana [4]). The in vitro particles also resemble the extrachromosomal nucleoli of amphibian oocytes (21,26,32) and a variety of in vivo structures referred to as nucleolus-like bodies (39,40,49,51), nucleolus-like "blobs" (23), or prenucleolar bodies (17,37,50). For convenience, we have adopted the terminology used by Swift and Stevens (51) and Stevens and Prescott (49).…”

Section: C) the Outer Layer Resembled The Gc Ofmentioning

confidence: 99%

“…Reformation of typical nucleoli requires the reactivation of rRNA transcription. If transcription is blocked after mitosis, nucleolar components reassociate in the nucleus into complexes described as prenucleolar bodies or nucleolus-like bodies (39,49).…”

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confidence: 99%

Nucleolus-like morphology produced during the in vitro reassociation of nucleolar components

Trimbur

Walsh

1993

The Journal of Cell Biology

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Abstract. Nucleoli, the sites of rRNA synthesis, rRNA processing, and the assembly of ribosomes, are dynamic organelles that, in most cells, disperse and reform during mitosis. The mechanisms that regulate nucleolar formation are unknown as is the relationship between nucleolar morphology and the pathway of ribosome biogenesis. In this report we describe the in vitro formation of nucleolus-like particles (NLPs) from soluble extracts of nucleoli. NLPs, which reached sizes comparable to nucleoli (1-3 #m), were found to contain 40% of the nucleolar DNA, RNA, and protein.The ultrastructure of NLPs resembled that of a number of in vivo structures including compact nucleoli, prenucleolar bodies, and pseudonucleoli. The particles were composed of two morphologically distinct regions. The core resembled the dense fibrillar component (DFC) of nucleoli while the cortex resembled the granular component (GC) of nucleoli. The cortex of NLPs contained numerous 15-20 nm osmophilic granules that resembled the preribosomes found in the GC of nucleoli.The distribution of nucleolar proteins in NLPs also resembled that in nucleoli. BN46/51, a component of the GC of nucleoli, was restricted to the GC-like cortex of NLPs. A mAb that bound to the DFC of nucleoli, bound only to the DFC-like core of NLPs while a second mAb that bound to both the DFC and GC of nucleoli, bound to both the core and cortex of NLPs. Thus solubilized components of nucleoli can reassociate in vitro to produce particles that resemble nucleoli in their size, ultrastructure, and protein distribution.

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Repopulation of Postmitotic Nucleoli by Preformed Rna

Cited by 23 publications

References 19 publications

Localization of ribosomal protein S1 in the granular component of the interphase nucleolus and its distribution during mitosis.

Localization of ribosomal protein S1 in the granular component of the interphase nucleolus and its distribution during mitosis.

Partially Processed pre-rRNA Is Preserved in Association with Processing Components in Nucleolus-derived Foci during Mitosis

Nucleolus-like morphology produced during the in vitro reassociation of nucleolar components

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