Biology of the Cell
0248-4900
Cơ quản chủ quản: WILEY , Wiley-Blackwell
Lĩnh vực:
Medicine (miscellaneous)Cell Biology
Phân tích ảnh hưởng
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Các bài báo tiêu biểu
Reversible disassembly of transcription domains in lymphocyte nuclei during inhibition of RNA synthesis by DRB Summary— We are investigating the roles of RNA synthesis, chromatin structure and nuclear matrix organization in establishing and maintaining transcription domains, using mitogen stimulated lymphocytes as a model system. In a continuing study, the effects of the RNA polymerase inhibitor DRB and of its removal on nuclear organization have been examined by EM cytochemistry and by immunofluorescence labelling of the nuclear matrix P11, Sm and nucleolar fibrillarin antigens. Chromatin, interchromatin granules and nucleoli were extensively restructured after DRB, as were matrix antigens. According to cytochemical staining properties, the conformation of DRB‐induced condensed chromatin resembled that in partially stimulated lymphocytes. The nucleoplasmic fibrogranular RNP network appeared little altered, but the fibrillar proteinaceous interchromatinic regions, interpreted as representing the nuclear matrix in situ , were more affected. After removal of DRB, nuclei recovered the organization and transcriptional activity of controls within 8 h. These results suggest that the matrix subtending transcription domains remains stable when transcription is arrested, even though the chromatin and individual RNP components of the domains are disorganized. The data further indicate that absence of transcription is not solely accountable for the highly aggregated state of the chromatin in resting lymphocytes.
Tập 78 - Trang 163-180 - 1993
Centrin is a component of the periocentriola lattice Summary— Here, we use three polyclonal anticentrin antisera designated 08/28, 26/14‐1, and 26/14‐2 to further characterize the pericentriolar lattice of metazoan cells. all of these antibodies give an indistinguishable localization pattern that consists of a constellation of pericentrosomal spots. In QT6 cells these spots are few in number and closely associated with the centriolar region, whereas in PtK2 cells they are more numerous and distributed further from the point of microtubule focus. In mitotic cells, centrin is localized to the spindle poles and spindle apparatus. We demonstrate here that the pericentriolar lattice of PtK2 and QT6 cells is, in part, composed of proteins characterized by acidic pI s (4.4 to 5.4), low molecular mass (M r 18 500–21000), and calcium‐binding; these attributes and the immunoreactivity of these proteins to anticentrin antibodies indicate that they are centrin isoforms of metazoan cells. Finally, we confirm our earlier observation that PtK2 cells contain a centrin‐related protein of M r 165000; QT6 cells also contain centrin‐related proteins (M r 64000–165000). We conclude that centrin is a component of the pericentriolar lattice of higher eukaryotic centrosomes.
Tập 76 - Trang 383-388 - 1992
Fibrillarin: a new protein of the nucleolus identified by autoimmune sera Autoimmune serum from a patient with scleroderma was shown by indirect immunofluorescence to label nucleoli in a variety of cells tested including: rat kangaroo PtK2, Xenopus A6, 3T3, HeLa, and human peripheral blood lymphocytes. Immunoblot analysis of nucleolar proteins with the scleroderma antibody resulted in the labeling of a single protein band of 34 kD molecular weight with a pI of 8.5. Electron microscopic immunocytochemistry demonstrated that the protein recognized by the scleroderma antiserum was localized exclusively in the fibrillar region of the nucleolus which included both dense fibrillar and fibrillar center regions. Therefore, we have named this protein “fibrillarin”. Fibrillarin was found on putative chromosomal nucleolar organizer regions (NORs) in metaphase and anaphase, and during telophase fibrillarin was found to be an early marker for the site of formation of the newly forming nucleolus. Double label indirect immunofluorescence and immunoelectron microscopy on normal, actinomycin D‐segregated, and DRB‐treated nucleoli showed that fibrillarin and nucleolar protein B23 were predominantly localized to the fibrillar and granular regions of the nucleolus, respectively. RNase A and DNase I digestion of cells in situ demonstrated that fibrillarin was partially removed by RNase and completely removed by DNase. These results suggest that fibrillarin is a widely occurring basic nonhistone nucleolar protein whose location and nuclease sensitivity may indicate some structural and/or functional role in the rDNA‐containing dense fibrillar and fibrillar center regions of the nucleolus.
Tập 54 Số 2 - Trang 123-133 - 1985
Nucleologenesis: use of non‐isotopic <i>in situ</i> hybridization and immunocytochemistry to compare the localization of rDNA and nucleolar proteins during mitosis Using in situ hybridization and immunocytochemistry during interphase and mitosis, we have compared the distribution of ribosomal DNA (rDNA) to that of the nucleolar proteins fibrillarin and RNA polymerase I. During interphase, nucleolar proteins were localized at sites throughout the nucleolus while the bulk of rDNA was localized in a single restricted nucleolar area. During metaphase and anaphase, all six NORs were detected by in situ hybridization, Ag‐staining, or by the immunolocalization of RNA polymerase I. During telophase, rDNA and RNA polymerase I were found in a distinct subset of the prenucleolar bodies (PNBs) which obviously must contain the nucleolar organizers. Other numerous PNBs are smaller in size and do not contain detectable amounts of rDNA or RNA polymerase I. Therefore, reconstruction of the nucleolus originates in telophase‐specific domains which contain both rDNA and RNA polymerase I.
Tập 65 Số 3 - Trang 239-246 - 1989
The nucleolus and transcription of ribosomal genes Abstract Ribosome biogenesis is a highly dynamic, steady‐state nucleolar process that involves synthesis and maturation of rRNA, its transient interactions with non‐ribosomal proteins and RNPs and assembly with ribosomal proteins. In the few years of the 21st century, an exciting progress in the molecular understanding of rRNA and ribosome biogenesis has taken place. In this review, we discuss the recent results on the regulation of rRNA synthesis in relation to the functional organization of the nucleolus, and put an emphasis on the situation encountered in mammalian somatic cells.
Tập 96 Số 8 - Trang 579-594 - 2004
Mouse neuroblastoma cells release prion infectivity associated with exosomal vesicles Background information . TSEs (transmissible spongiform encephalopathies) are neurodegenerative disorders affecting humans and animals. PrPSc , a conformationally altered isoform of the normal prion protein (PrPC ), is thought to be the pathogenic agent. However, the biochemical composition of the prion agent is still matter of debate. The potential transmission risk of the prion agent through biological fluids has been shown, but the development of competitive diagnostic tests and treatment for TSEs requires a more comprehensive knowledge of the agent and the cellular mechanisms by which it is disseminated. With this aim, we initiated characterization of the prion agent and the pathways by which it can be propagated using the cellular model system neuroblastoma (N2a).Results . The present study shows that N2a cells infected with scrapie release the prion agent into the cell culture medium in association with exosome‐like structures and viral particles of endogenous origin. We found that both prion proteins and scrapie infectivity are mainly associated with exosome‐like structures that contain viral envelope glycoprotein and nucleic acids, such as RNAs.Conclusions . The dissemination of prions in N2a cell culture is mediated through the exosomal pathway.
Tập 100 Số 10 - Trang 603-618 - 2008
The aquaporin-Z water channel gene of Escherichia coli: Structure, organization and phylogeny
Tập 89 - Trang 321-329 - 1997
Transmembrane scaffolding proteins in the formation and stability of nodes of Ranvier Abstract The function of myelinated fibers depends on the clustering of sodium channels at nodes of Ranvier, the integrity of the myelin sheath, and the existence of tight axoglial junctions at paranodes, on either sides of the nodes. While the ultrastructure of these regions has been known for several decades, recent progress has been accomplished in the identification of proteins essential for their organization, which depends on the interplay between axons and myelinating glial cells. Evolutionary conserved intercellular multimolecular complexes comprising proteins of the Neurexin IV/Caspr/paranodin (NCP) family and of the immunoglobulin‐like cell adhesion molecules superfamily, are essential components for the axoglial contacts at the level of paranodes and juxtaparanodes. These complexes are able to interact with cytoplasmic proteins of the band 4.1 family, providing possible links to the axonal cytoskeleton. While the identification of these proteins represents a significant progress for understanding axoglial contacts, they also raise exciting questions concerning the molecular organization of these contacts and the mechanisms of their local enrichment.
Tập 95 - Trang 447-452 - 2003