scholarly journals Nuclear RNA Is Extruded from Apoptotic Cells

1998 ◽  
Vol 46 (9) ◽  
pp. 999-1005 ◽  
Author(s):  
Marco Biggiogera ◽  
Maria Grazia Bottone ◽  
Carlo Pellicciari
Keyword(s):  
Appreciable Amount ◽  
Apoptotic Cells ◽  
Spontaneous Apoptosis ◽  
Systemic Autoimmune Diseases ◽  
Nucleolar Material ◽  
Nuclear Rna ◽  
Interchromatin Granules ◽  
Possible Cause ◽  
Perichromatin Granules ◽  
Perichromatin Fibrils

During spontaneous apoptosis of thymocytes there is extrusion of ribonucleoproteins (RNPs) from the cell. The aim of this investigation was to elucidate whether the RNP aggregates in apoptotic cells and bodies still contain RNA in an appreciable amount. We demonstrated by specific cytochemical techniques that the aggregates of nuclear RNPs extruded in the cytoplasm of spontaneously apoptotic thymocytes contain RNA in a sufficient amount to be detected cytochemically. These heterogeneous ectopic RNP-derived structures (HERDS) are formed by perichromatin fibrils, interchromatin granules, perichromatin granules, and nucleolar material. The RNA detected inside these clusters should therefore correspond to both mRNA and snRNA as well as to rRNA. We never observed DNA-contaning aggregates in the cytoplasm of apoptotic thymocytes. The presence of RNA in the HERDS that may be released from apoptotic cells suggests that the decrease in the amount of total RNA during apoptosis may be mostly linked to cellular extrusion rather than to degradation of RNA by RNase activities. Another interesting aspect of these results lies in the hypothesis of apoptosis as a possible cause for the presence of autoantibodies in the serum of patients with systemic autoimmune diseases.

Use of human autoantibodies and immunoelectron microscopy to study structure and function of the nucleolus and nuclear bodies

1992 ◽  
Vol 50 (1) ◽  
pp. 506-507
Author(s):  
Robert L. Ochs
Keyword(s):  
Electron Microscopy ◽  
Structure And Function ◽  
Nuclear Bodies ◽  
Nuclear Interior ◽  
Coiled Bodies ◽  
Interchromatin Granules ◽  
And Function ◽  
Conventional Electron Microscopy ◽  
Perichromatin Granules ◽  
Perichromatin Fibrils

By conventional electron microscopy, the formed elements of the nuclear interior include the nucleolus, chromatin, interchromatin granules, perichromatin granules, perichromatin fibrils, and various types of nuclear bodies (Figs. 1a-c). Of these structures, all have been reasonably well characterized structurally and functionally except for nuclear bodies. The most common types of nuclear bodies are simple nuclear bodies and coiled bodies (Figs. 1a,c). Since nuclear bodies are small in size (0.2-1.0 μm in diameter) and infrequent in number, they are often overlooked or simply not observed in any random thin section. The rat liver hepatocyte in Fig. 1b is a case in point. Historically, nuclear bodies are more prominent in hyperactive cells, they often occur in proximity to nucleoli (Fig. 1c), and sometimes they are observed to “bud off” from the nucleolar surface.

scholarly journals Ribonucleoprotein components in liver cell nuclei as visualized by cryoultramicrotomy.

1975 ◽  
Vol 67 (1) ◽  
pp. 200-214 ◽  
Author(s):  
E Puvion ◽  
W Bernhard
Keyword(s):  
Cell Nuclei ◽  
Glutaraldehyde Fixation ◽  
Rat Hepatocyte ◽  
Colloidal Iron ◽  
Dna Structures ◽  
Normal Rat ◽  
Ultrathin Frozen Sections ◽  
Interchromatin Granules ◽  
Perichromatin Granules ◽  
Perichromatin Fibrils

The interphase nucleus of the normal rat hepatocyte has been studied in ultrathin frozen sections after glutaraldehyde fixation and the modification of various staining procedures known to be specific for DNA structures (Moyne's thallium stain, Gautier's osmium-ammine) or preferential for RNP carriers and basic proteins (regressive stains based on the use of EDTA or citrate, negatively charged colloidal iron). The results are comparable to those obtained after classical dehydration and embedding. Particular attention has been paid to the nucleolus and extranucleolar RNP components, such as perichromatin fibrils and granules, as well as interchromatin granules. A striking observation was the uneven size and the strongly increased number of perichromatin granules, and the appearance of a contiguous interchromatin net, containing nucleoproteins. Cryoultramicrotomy without embedding appears to be very useful for the exploration of the nucleus in thick sections which remain sufficiently transparent even with the usual accelerating voltages.

scholarly journals Ultrastructural distribution of nuclear ribonucleoproteins as visualized by immunocytochemistry on thin sections.

1984 ◽  
Vol 98 (1) ◽  
pp. 358-363 ◽  
Author(s):  
S Fakan ◽  
G Leser ◽  
T E Martin
Keyword(s):  
Protein A ◽  
Nuclear Architecture ◽  
Gold Complex ◽  
Thin Sections ◽  
Border Regions ◽  
Core Proteins ◽  
Interchromatin Granules ◽  
Lowicryl K4m ◽  
Perichromatin Fibrils

The ultrastructural distribution of nuclear ribonucleoproteins (RNP) has been investigated by incubation of thin sections of mouse or rat liver, embedded in Lowicryl K4M or prepared by cryoultramicrotomy, with antibodies specific for RNP. The antibodies were localized by means of a protein A-colloidal gold complex. Anti-small nuclear (sn)RNP antibodies, specific for determinants of the nucleoplasmic snRNP species containing U1, U2, U4, U5, and U6 RNAs, were found associated preferentially with perichromatin fibrils, interchromatin granules, and coiled bodies. This indicates an early association of snRNP with structural constituents containing newly synthesized heterogeneous nuclear RNA. It also suggests a possible structural role of some snRNPs in nuclear architecture. Antibodies against the core proteins of heterogeneous nuclear RNP particles associate preferentially with the border regions of condensed chromatin, and in particular with perichromatin fibrils and some perichromatin granules. These results are discussed in view of recent knowledge about the possible role of nucleoplasmic RNP-containing components in the functions of the cell nucleus.

scholarly journals Organization of Highly Acetylated Chromatin around Sites of Heterogeneous Nuclear RNA Accumulation

1998 ◽  
Vol 9 (9) ◽  
pp. 2491-2507 ◽  
Author(s):  
Michael J. Hendzel ◽  
Michael J. Kruhlak ◽  
David P. Bazett-Jones
Keyword(s):  
Histone Deacetylases ◽  
Active Regions ◽  
Fibroblast Cell ◽  
Cell Nuclei ◽  
Transmission Electron ◽  
Interchromatin Granule ◽  
Nuclear Rna ◽  
Interchromatin Granules ◽  
The Individual ◽  
Rna Accumulation

Histones found within transcriptionally competent and active regions of the genome are highly acetylated. Moreover, these highly acetylated histones have very short half-lives. Thus, both histone acetyltransferases and histone deacetylases must enrich within or near these euchromatic regions of the interphase chromatids. Using an antibody specific for highly acetylated histone H3, we have investigated the organization of transcriptionally active and competent chromatin as well as nuclear histone acetyltransferase and deacetylase activities. We observe an exclusion of highly acetylated chromatin around the periphery of the nucleus and an enrichment near interchromatin granule clusters (IGCs). The highly acetylated chromatin is found in foci that may reflect the organization of highly acetylated chromatin into “chromonema” fibers. Transmission electron microscopy of Indian muntjac fibroblast cell nuclei indicates that the chromatin associated with the periphery of IGCs remains relatively condensed, most commonly found in domains containing chromatin folded beyond 30 nm. Using electron spectroscopic imaging, we demonstrate that IGCs are clusters of ribonucleoprotein particles. The individual granules comprise RNA-rich fibrils or globular regions that fold into individual granules. Quantitative analysis of individual granules indicates that they contain variable amounts of RNA estimated between 1.5 and >10 kb. We propose that interchromatin granules are heterogeneous nuclear RNA-containing particles, some of which may be pre-mRNA generated by nearby transcribed chromatin. An intermediary zone between the IGC and surrounding chromatin is described that contains factors with the potential to provide specificity to the localization of sequences near IGCs.

scholarly journals Subnuclear Localization and Dynamics of the Pre-mRNA 3′ End Processing Factor Mammalian Cleavage Factor I 68-kDa Subunit

2007 ◽  
Vol 18 (4) ◽  
pp. 1282-1292 ◽  
Author(s):  
Stefano Cardinale ◽  
Barbara Cisterna ◽  
Paolo Bonetti ◽  
Chiara Aringhieri ◽  
Marco Biggiogera ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Ultrastructural Level ◽  
Essential Factor ◽  
Processing Factor ◽  
Nuclear Speckles ◽  
Subnuclear Localization ◽  
Factor I ◽  
Active Transcription ◽  
Interchromatin Granules ◽  
Perichromatin Fibrils

Mammalian cleavage factor I (CF Im) is an essential factor that is required for the first step in pre-mRNA 3′ end processing. Here, we characterize CF Im68 subnuclear distribution and mobility. Fluorescence microscopy reveals that in addition to paraspeckles CF Im68 accumulates in structures that partially overlap with nuclear speckles. Analysis of synchronized cells shows that CF Im68 distribution in speckles and paraspeckles varies during the cell cycle. At an ultrastructural level, CF Im68 is associated with perichromatin fibrils, the sites of active transcription, and concentrates in interchromatin granules-associated zones. We show that CFIm68 colocalizes with bromouridine, RNA polymerase II, and the splicing factor SC35. On inhibition of transcription, endogenous CF Im68 no longer associates with perichromatin fibrils, but it can still be detected in interchromatin granules-associated zones. These observations support the idea that not only splicing but also 3′ end processing occurs cotranscriptionally. Finally, fluorescence recovery after photobleaching analysis reveals that the CF Im68 fraction associated with paraspeckles moves at a rate similar to the more dispersed molecules in the nucleoplasm, demonstrating the dynamic nature of this compartment. These findings suggest that paraspeckles are a functional compartment involved in RNA metabolism in the cell nucleus.

scholarly journals Fine Structural Specific Visualization of RNA on Ultrathin Sections

1998 ◽  
Vol 46 (3) ◽  
pp. 389-395 ◽  
Author(s):  
Marco Biggiogera ◽  
Stanislav Fakan
Keyword(s):  
Rnase A ◽  
Electron Microscopic Level ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Acrylic Resins ◽  
Cell Components ◽  
Ultrathin Sections ◽  
A New Technique ◽  
Interchromatin Granules ◽  
Perichromatin Granules

We describe a new technique that allows specific visualization of RNA at the electron microscopic level by means of terbium citrate. Under the conditions presented here, terbium binds selectively to RNA and stains nucleoli, interchromatin granules, perichromatin fibrils, perichromatin granules, and coiled bodies in the cell nucleus, whereas ribosomes are the only contrasted structures in the cytoplasm. All the cell components contrasted by terbium are known to contain RNA. When ultrathin sections are pretreated with RNase A or nuclease S1 (specific for single-stranded nucleic acids), staining does not occur. Neither DNase nor pronase influences the reaction. We conclude that terbium staining is selective for RNA and especially for single-stranded RNA. The staining can be performed on thin sections of material embedded both in epoxy and in acrylic resins. The technique is not influenced by the aldehyde fixative used and can also be utilized after immunolabeling. The endproduct is very fine and, although weak in contrast, is suitable for high-resolution observations.

scholarly journals A STUDY OF THE NUCLEOLAR MATERIAL IN SCIARA COPROPHILA

1966 ◽  
Vol 29 (2) ◽  
pp. 347-359 ◽  
Author(s):  
Natalia Gabrusewycz-Garcia ◽  
Ruth G. Kleinfeld
Keyword(s):  
Rna Synthesis ◽  
Polytene Chromosomes ◽  
Nucleolar Organizer ◽  
Prepupal Stage ◽  
Large Numbers ◽  
Nucleolar Material ◽  
Wide Range ◽  
Nuclear Rna ◽  
Dna Puffs ◽  
Range Of Variation

In the polytene chromosomes of Sciara coprophila, in addition to a nucleolus, large numbers of nucleolarlike structures or micronucleoli are formed. A detailed mapping localized the nucleolar organizer at one end of the X chromosome and revealed that approximately 18% of the bands of each chromosome are potentially capable of producing micronucleoli. Most of these sites are in regions known from a previous study to show asynchronous DNA replication: DNA puffs and certain heterochromatic regions. Micronucleoli are rarely found in association with bulbs. The RNA metabolism of the polytene chromosomes during late fourth instar was studied using radioautographic techniques. Isolated glands were incubated in tritiated uridine for 10 to 30 min, and radioautographs were made of squash preparations. Despite the wide range of variation found among different larval cultures, the following pattern was observed. Just prior to and at the beginning of DNA puff formation, a period of intense extrachromosomal nucleolar and micronucleolar RNA synthesis occurs. After maximal development of the DNA puffs, the synthesis of extrachromosomal RNA is at a low point, while incorporation into bulbs and DNA puffs remains high. With the onset of the prepupal stage, all nuclear RNA synthesis ceases.

Structure and dynamics of hnRNP-labelled nuclear bodies induced by stress treatments

2000 ◽  
Vol 113 (22) ◽  
pp. 4043-4053 ◽  
Author(s):  
I. Chiodi ◽  
M. Biggiogera ◽  
M. Denegri ◽  
M. Corioni ◽  
F. Weighardt ◽  
...  
Keyword(s):  
Heat Shock ◽  
Nuclear Bodies ◽  
Cadmium Sulfate ◽  
The Core ◽  
Hnrnp Proteins ◽  
Before And After ◽  
Hnrnp Protein ◽  
Response To Stress ◽  
Perichromatin Granules ◽  
Perichromatin Fibrils

We have previously described HAP, a novel hnRNP protein that is identical both to SAF-B, a component of the nuclear scaffold, and to HET, a transcriptional regulator of the gene for heat shock protein 27. After heat shock, HAP is recruited to a few nuclear bodies. Here we report the characterisation of these bodies, which are distinct from other nuclear components such as coiled bodies and speckles. The formation of HAP bodies is part of a general cell response to stress agents, such as heat shock and cadmium sulfate, which also affect the distribution of hnRNP protein M. Electron microscopy demonstrates that in untreated cells, similar to other hnRNP proteins, HAP is associated to perichromatin fibrils. Instead, in heat shocked cells the protein is preferentially associated to clusters of perichromatin granules, which correspond to the HAP bodies observed in confocal microscopy. Inside such clusters, perichromatin granules eventually merge into a highly packaged ‘core’. HAP and hnRNP M mark different districts of these structures. HAP is associated to perichromatin granules surrounding the core, while hnRNP M is mostly detected within the core. BrU incorporation experiments demonstrate that no transcription occurs within the stress-induced clusters of perichromatin granules, which are depots for RNAs synthesised both before and after heat shock.

Sign in / Sign up

Export Citation Format

Share Document