Navegando por Palavras-chave "nucleolus"
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- ItemSomente MetadadadosThe behavior of the coiled body in cells infected with adenovirus in vitro(Kluwer Academic Publ, 1996-01-01) Rodrigues, S. H.; Silva, N. P.; Delicio, L. R.; Granato, C.; Andrade, LEC; Universidade Federal de São Paulo (UNIFESP)The coiled body is a phylogenetically conserved nuclear organelle whose function is not known. Probes for detection of p80-coilin, an 80 kDa protein enriched in the coiled body, have made possible studies determining the behavior of the coiled body during the cell cycle, in proliferating cells, as well as reports suggesting some relationship of the coiled body to mRNA splicing and to the nucleolus. the objective of this study is to examine the distribution of p80-coilin and nucleolar proteins in cells infected with adenovirus in vitro. HeLa cells grown as monolayers were infected with successive dilutions of type 5 human adenovirus culture and fixed in methanol/acetone at different time points. Single and double indirect immunofluorescence was performed with human autoantibodies to p80-coilin, fibrillarin, NOR-90/hUBF, RNA polymerase I, PM-Sd, and To, as well as rabbit polyclonal serum to p80-coilin (R288) and mouse monoclonal antibody to adenovirus 72-kDa DNA-binding protein. Indirect immunofluorescence (IIF) with anti- p80-coilin antibodies showed that the usual bright dot-like coiled body staining pattern was replaced in infected cells by 1-5 clusters of tiny dots at the periphery of the nucleus. This phenomenon was first detected within 12 h of infection and affected more severely cells with increased length and load of infection. Cells subjected to heat shock presented no such alteration. Double IIF showed that cells with abnormal coiled body appearance expressed the viral 72-kDa DNA-binding protein. Nucleolar proteins RNA polymerase I and NOR-90/hUBF became associated with the p80-coilin-enriched clusters and were no longer detected in the nucleolus. Other nucleolar proteins, like PM-Sd and To, remained associated to the nucleolus and were not detected in the newly formed clusters. Fibrillarin had a heterogeneous behavior, being restricted to the nucleolus in some infected cells while in some others it was associated with the p80-coilin-enriched clusters. Thus our results showed that in vitro adenovirus infection induced radical redistribution of nucleolar and coiled body constituents into newly formed structures characterized by clusters of tiny dots in the periphery of the nucleus. the fact that three major proteins involved in rRNA synthesis and processing colocalized with p80-coilin in these clusters may bring additional support to the idea that the coiled body and p80-coilin may be implicated in functions related to the nucleolus.
- ItemSomente MetadadadosNuclear subcompartments: an overview(Wiley-Blackwell, 2017) Nunes, Vinicius Santana [UNIFESP]; Moretti, Nilmar Silvio [UNIFESP]The advance in biochemical and microscopy techniques has revealed the complexity and intricate nucleoplasm structure. Several subcompartments were identified in nucleus and the importance of these subcompartments in processes crucial for normal nuclear activity has been demonstrated. In this mini-review, we will give an overview about the composition, function, and importance of the major nuclear subcompartments. Also, we will show the impact that perturbing these structures can cause in normal nuclear activity, and how these can contribute to the development of some human diseases.
- ItemSomente MetadadadosThree-Dimensional Reconstruction of Trypanosoma cruzi Epimastigotes and Organelle Distribution Along the Cell Division Cycle(Wiley-Blackwell, 2011-07-01) Ramos, Thiago Cesar Prata [UNIFESP]; Freymüller-Haapalainen, Edna [UNIFESP]; Schenkman, Sergio [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)Trypanosoma cruzi is the protozoan that causes Chagas disease. It divides in the insect vector gut or in the cytosol of an infected mammalian cell. T cruzi has one mitochondrion, one Golgi complex, one flagellum, and one cytostome. Here, we provide three-dimensional (3D) models of this protozoan based on images obtained from serial sections on electron microscopy at different stages of the cell cycle. Ultrathin serial sections were obtained from Epon (TM) embedded parasites, photographed in a transmission electron microscope, and 3D models were generated using Reconstruct and Blender 3D modeling softwares. the localization and distribution of organelles was evaluated and attributed to specific morphological patterns and deduced by distribution of specific markers by immunofluorescence analysis. the new features found in the 3D reconstructions are (1) the electron-dense chromatin is interconnected leaving an internal space for a centrally located nucleolus; (2) the kinetoplast is accommodated within a separated branch of the tubular and single mitochondrion; (3) the disk shaped kinetoplast, which is the mitochondrial DNA, duplicates from the interior in G2 phase; (4) the mitochondrion faces the external membrane and shrinks to accommodate an enlarged number of cytosolic vesicles from G1 to G2; (5) the cytostome progress from the parasite surface toward the posterior end contouring the kinetoplast and nucleus and retracts during cell cycle. These new observations might help understanding how organelles are formed and distributed in early divergent eukaryotic cells and provides a useful method to understand the organelle distribution in small eukaryotic cells. (C) 2011 International Society for Advancement of Cytometry
- ItemSomente MetadadadosTranscription rate modulation through the Trypanosoma cruzi life cycle occurs in parallel with changes in nuclear organisation(Elsevier B.V., 2001-01-15) Elias, MCQB; Marques-Porto, R.; Freymuller, E.; Schenkman, S.; Universidade Federal de São Paulo (UNIFESP)In trypanosomes transcription occurs as large polycistronic units, with trans-splicing and polyadenylation generating each individual mRNA. There are no defined RNA. polymerase II promoters and mRNA stabilisation is most likely the process controlling levels of differentially expressed mRNAs, since no selective modulation of gene activity has even been reported at the transcriptional level. Here, we show a large decrease in the transcription rates by RNA polymerases I and II when proliferative forms of Trypanosoma cruzi (epimastigotes and amastigotes) transform into non-proliferative and infective forms (trypomastigotes). We also show that these changes in transcription occur in parallel with modifications in the nuclear structure. While nuclei of proliferative forms are round, contain small amounts of peripheral heterochromatin and a large nucleolus, nuclei of trypomastigotes are elongated, the nucleolus disappears and the heterochromatin occupies most of the nuclear compartment. the decrease in the transcription parallels the nucleolus disassembly, as seen by the dispersion of nucleolar antigens. As T. cruzi cycles continuously through proliferative and infective forms, the molecular mechanisms involved in the control of nuclear organisation and chromatin remodelling can be revealed by this system. (C) 2001 Elsevier Science B.V. All rights reserved.