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At least 685 records · Page 38Linked to original sources
PubMed1989

Association of adenovirus DNA transcribed activity with nuclear matrix of host cells.

With gentle cell extraction techniques, various DNA components in the HeLa cells after 6 h of adenovirus infection have been obtained. Adenovirus, early transcribed regions (E2a, E1b) and a late transcribed region (L2) were used as probes in Southern hybridization, respectively. The experiment showed that only actively transcribed adenovirus DNA fragments would tightly bind to the nuclear matrix of host cells. We inferred that the nuclear matrix of host cells plays an important role in viral DNA transcription.

Adenoviridae↗
PubMed1990

[Proteolytic degradation of nuclear matrix proteins in the rat liver, Zajdela's hepatoma and hepatoma 22A in the presence of ATP].

An intense proteolytic degradation of both proteins and phosphoproteins has been observed in isolated nuclear matrices from rat liver, Zajdela Hepatoma and Hepatoma 22a, incubated with NP-40, DTT and gamma-[32P] ATP being most intense in Hepatoma 22a. Practically all phosphoproteins of Hepatoma 22a nuclear matrix degraded. This implies either an extremely high proteolytic activity in the preparation or the presence of a specific to phosphoproteins protease absent from rat liver and Zajdela Hepatoma nuclear matrices.

Adenosine Triphosphate↗
PubMed2004

Distinct LIM domains of Hic-5/ARA55 are required for nuclear matrix targeting and glucocorticoid receptor binding and coactivation.

Hydrogen peroxide-inducible clone-5 (Hic-5), belongs to the group III LIM domain protein family and contains four carboxyl-terminal LIM domains (LIM1-LIM4). In addition to its role in focal adhesion signaling, Hic-5 acts in the nucleus as a coactivator for some steroid hormone receptors such as the glucocorticoid receptor (GR) and androgen receptor (AR). Based upon its effect on AR transactivation, Hic-5 has also been designated as ARA55. Here, we report mapping studies of Hic-5/ARA55 functional domains and establish that LIM3 and LIM4 are necessary for maximal effects on GR transactivation. However, results from yeast two-hybrid assays demonstrated that these two LIM domains together, while necessary, are not sufficient to interact with the tau2 transactivation domain of GR. LIM4 also functions as a nuclear matrix targeting sequence (NMTS) for Hic-5/ARA55, as it is both necessary and sufficient to target a heterologous protein to the nuclear matrix. Thus, as suggested from previous analysis of LIM domain-containing proteins, separate but highly related LIM domains serve distinct functions.

Animals↗
PubMed1995

Nuclear domains and the nuclear matrix.

This overview describes the spatial distribution of several enzymatic machineries and functions in the interphase nucleus. Three general observations can be made. First, many components of the different nuclear machineries are distributed in the nucleus in a characteristic way for each component. They are often found concentrated in specific domains. Second, nuclear machineries for the synthesis and processing of RNA and DNA are associated with an insoluble nuclear structure, called nuclear matrix. Evidently, handling of DNA and RNA is done by immobilized enzyme systems. Finally, the nucleus seems to be divided in two major compartments. One is occupied by compact chromosomes, the other compartment is the space between the chromosomes. In the latter, transcription takes place at the surface of chromosomal domains and it houses the splicing machinery. The relevance of nuclear organization for efficient gene expression is discussed.

Animals↗
PubMed2003

Limited capacity of the nuclear matrix to bind telomere repeat binding factor TRF1 may restrict the proliferation of mortal human fibroblasts.

The maintenance of telomere integrity is essential for prolonged cell proliferation, and failure in this mechanism is a most consistent manifestation of cellular senescence. In this study, we investigated the role of telomere repeat binding factor (TRF1) in the proliferation of human fibroblasts. TRF1 expression is upregulated in a large variety of immortal human cells and supports de novo telomere formation in a dose-dependent manner. These observations suggest that the suppression of TRF1 might limit telomere maintenance and thus the life span of mortal cells. However, primary fibroblasts ectopically overexpressing TRF1 were unable to avoid senescence. On the other hand, exogenously expressed TRF1 in primary fibroblasts neither supported de novo telomere formation nor bound to the nuclear matrix as tightly as observed in immortal cells that show upregulated TRF1 expression. We present evidence suggesting that mortal human cells lack specific ligand(s) that anchor TRF1 to the nuclear matrix and that this contributes to their limited lifespan.

Cell Division↗
PubMed1979

The nuclear matrix of slowly and rapidly proliferating liver cells.

The nuclear matrix of slowly proliferating rat liver is compared with rapidly proliferating regenerating liver and Zajdela ascites hepatoma cells. While no differences are detected in overall ultrastructure, composition or polypeptide profiles of normal liver versus regenerating liver matrices, significant alterations are observed in the polypeptides of Zajdela hepatoma nuclear matrices.

Animals↗
PubMed1988

[Changes in the interaction of DNA with chromatin and nuclear matrix proteins during digestion of nuclei with restrictases and nuclease Bal 31].

Earlier experiments with the use of nucleoprotein-celite chromatography revealed that DNA is bound to a replicative complex localized in the nuclear matrix by a topologically tight bond. Induction of site-specific DNA breaks by restriction nucleases in isolated nuclei of proliferating cells causes a gradual concentration-dependent liberation of DNA from the tight binding to the nuclear matrix. The DNA involved in the tight interaction with matrix proteins is especially sensitive to digestion by Sau 3A1, EcoRI, PstI, BCNI and Bam HI restrictases. One-strand DNA-specific nuclease Bal 31 also destroys the tight DNA-matrix bond. The tightness of DNA-protein bonds in chromatin particles formed after the digestion of nuclei with restrictases is dependent on the particle size. The data are summarized in a model of a topological DNA-matrix bond.

Chromatin↗
PubMed1997

The product of the US10 gene of herpes simplex virus type 1 is a capsid/tegument-associated phosphoprotein which copurifies with the nuclear matrix.

We have identified the herpes simplex virus type 1 (HSV-1) US10 gene product using rabbit polyclonal antisera raised against a recombinant 6xHis-US10 fusion protein expressed in Escherichia coli. The antiserum reacted specifically with 34 and 36 kDa proteins in HSV-1 KOS-infected cells as shown by Western blotting and immunoprecipitation experiments. The 36 kDa protein was immunoprecipitated with the US10 antiserum from 32P-labelled lysates of Vero cells infected with HSV-1 KOS, demonstrating that the US10 protein was phosphorylated. Indirect immunofluorescence studies localized the US10 protein mainly to nuclei as large discrete particles at later times post-infection (p.i.), and nuclear fractionation studies revealed that the protein was tightly associated with the nuclear matrix. Moreover, analysis of isolated intracellular capsids showed that both phosphorylated and unphosphorylated forms of the US10 product were also associated with the capsid/tegument. These results indicate that the US10 gene of HSV-1 encodes a capsid/tegument-associated phosphoprotein which copurifies with the nuclear matrix.

Animals↗
PubMed1997

A c-erbB-2 promoter-specific nuclear matrix protein from human breast tumor tissues mediates NF-kappaB DNA binding activity.

The c-erbB-2 gene overexpression plays a major role in the pathogenesis of breast cancer. Binding studies detected a nuclear matrix protein (NMP) in human breast tumor tissues that recognizes a matrix attachment region (MAR) in the immediate vicinity of the c-erbB-2 gene promoter. This NMP is expressed in breast tumor tissues and cell lines along with c-erbB-2, but is not found in corresponding normal tissues. Furthermore, when NMP purified from the breast tumors by its affinity to the MAR sequence is added to nuclear extracts of breast cancer cells, it selectively stimulates the binding of the NF-kappaB transcription factor to DNA. A model is suggested in which the association of the MAR-like sequence with the nuclear matrix raises the local concentration of the specific NMP, which in turn interacts with the nuclear factor NF-kappaB to increase its local level. Such a complex could explain at a molecular level the "increase in NF-kappaB DNA binding activity" often observed in c-erbB-2- and BRCA1-positive human breast tumors. The increased NF-kappaB activity could thereby contribute to breast cancer progression.

Antigens, Nuclear↗
PubMed1982

[Localization of high-molecular alkali-insoluble polypeptides of rat liver cell nuclear matrix revealed by immunological methods].

By means of chicken immunization, antibodies were obtained to two high molecular weight polypeptides of an alkali-insoluble highly dispersed fraction of rat liver cell nuclear matrix. Using methods of indirect immunofluorescence these antibodies were seen fixed selectively on the periphery of the cell nuclei of rat liver, cultured human fibroblasts and of cultured human fibrosarcoma 8387 cells. The same pattern of antibody fixation, with non-specific net-like staining in the cytoplasm, was observed in the light microscope after the immunoperoxidase staining. Using the similar peroxidase staining with electron microscopy, antibody fixation was recorded with nuclear pore complexes, ribosomes, fibrous lamina and intranuclear granular structures in isolated rat liver cell nuclei and in the nuclear matrix. In mitotic cells the cytoplasm displayed a bright fluorescence, whereas the condensed chromosomes showed a fainter fluorescence. Thus, the examined high molecular weight antigens revealed no organ or species specificity. They appear to be constituents of nonmembraneous structures of the nuclear envelope, more likely of the pore complexes.

Animals↗
PubMed1993

Autoantibodies to a novel cell cycle-regulated protein that accumulates in the nuclear matrix during S phase and is localized in the kinetochores and spindle midzone during mitosis.

We have employed human autoantibodies to characterize a novel cell cycle-regulated nuclear protein, provisionally designated p330d (doublet polypeptide of 330 kDa). The expression and intracellular distribution of this protein was followed throughout the cell cycle using immunofluorescence microscopy, laser confocal microscopy, immunoelectron microscopy and flow cytometry. p330d was expressed only in proliferating cells and began accumulating in the nucleus during early S phase. The protein reached maximum expression levels during G2/M. In situ extractions with detergent, salt and nucleases failed to abolish the nuclear staining of interphase cells, suggesting a tight binding of p330d to the nuclear matrix during interphase. p330d was concentrated in the kinetochores during prophase but was relocated to the spindle midzone at the onset of anaphase. By late telophase, it was localized predominantly in the intercellular bridge regions flanking the midbody and disappeared gradually as the daughter cells separated. Immunoblotting analysis showed that the autoimmune sera recognized a doublet of 330 kDa, and affinity-purified antibodies from this doublet reproduced the fluorescence staining pattern of the whole serum. We propose that p330d is a novel member of the class of 'chromosomal passenger' proteins, which are associated transiently with centromeres during early mitosis and are then redistributed to other sites of the mitotic apparatus after the metaphase/anaphase transition. Possible in vivo functions for p330d and related proteins might include roles in centromere/kinetochore maturation and assembly, chromosome segregation, central spindle stabilization and cytokinesis.

Autoantibodies↗
PubMed2004

DNA replication initiates at domains overlapping with nuclear matrix attachment regions in the xenopus and mouse c-myc promoter.

Only a very few origins have been mapped in different multicellular organisms, and they do not share detectable consensus sequence elements. Moreover, it is not clear if origins are localized at similar positions in the corresponding locus in genomes of different organisms. Here, we have mapped DNA replication origins in the c-myc locus both in Xenopus and mouse, allowing a comparison of the corresponding sites in three different animal species (Xenopus, mouse, human). An origin of DNA replication is present in the three homologous c-myc loci. In Xenopus, a main DNA replication origin was located 3 kilobases (kb) upstream of the active c-myc promoter, whereas, in mouse, we detected an origin 1 kb upstream of the promoter, as previously mapped in human c-myc. We also identified a nuclear matrix attachment region in both Xenopus and mouse, which is localized to two different regions of the c-myc promoter region. However, in both cases, the nuclear matrix attachment sites are close to the DNA replication origin mapped in the locus. These data suggest that global features of chromatin organization in different organisms may contribute to DNA replication origin localization.

Animals↗
PubMed1994

Recovery of nuclear matrix ultrastructure of interphase CHO cells after heat shock.

Heat shock induces changes in G1 CHO cell nuclear matrix (NM) ultrastructure that may be related to heat-induced nuclear protein accumulation (Wachsberger and Coss, 1993, J. Cell. Physiol., 155:615-634). The present study quantitates recovery of alterations in NM fine structure in CHO cells heated in G1 and compares structural recovery with recovery of bulk RNA synthesis and surviving fraction (SF). Morphology of NM preparations was quantified 30 min and 20 hr following heat shock by 1) measurement of the number of fiber anastomosing points per unit area per NM, and 2) measurement of the length of fibers between points of anastomoses within individual NMs. Architectural recovery was nearly complete within 20 hr in cells heated at 43 degrees C or 45 degrees C with SFs of 0.27 or greater. No recovery of architecture was observed in heated cells with SFs of approximately 0.01 or less. The residual damage to NMs was associated with RNA-containing fiber networks as determined by means of RNase gold labeling. Recovery from inhibition of RNA synthesis following heat shock was related to recovery of NM architecture. It is suggested that 1) repair of NM architecture does not require full recovery of bulk RNA synthesis, and 2) partial or complete irreversible collapse of the NM may be responsible, in part, for heat-induced, interphase cell death.

Animals↗
PubMed1991

Nuclear matrix bound V(D)J recombination activity in rat thymus nuclei: an in vitro system.

We report here that a high level of V(D)J recombination activity is tightly associated with high-salt-resistant nuclear matrix isolated from thymus glands from 2- to 3-week-old rats. The soluble nuclear fractions either were devoid of or contained a very low level of recombinase activity. This is the first time that the process mimicking V(D)J recombination has been achieved in an in vitro system. The matrix-bound V(D)J recombinase activity was further found to be lymphoid specific, detectable only during early stages of development. These observations suggest that in vitro recombination of V(D)J segments of genes encoding antigen-binding proteins could be a matrix-bound process and that the nuclear matrix may be an important intranuclear domain for the functional organization of the V(D)J recombinase system.

Animals↗
PubMed2003

The transcriptional enhancer of the pea plastocyanin gene associates with the nuclear matrix and regulates gene expression through histone acetylation.

The influence of the transcriptional enhancer of the pea plastocyanin gene (PetE) on the acetylation of histones was examined with chromatin immunoprecipitation (ChIP) experiments using antibodies that recognize acetylated or nonacetylated histones H3 and H4. In transgenic tobacco plants containing the pea PetE promoter fused to uidA, both acetylated and nonacetylated histones H3 and H4 were present on the integrated transgene. Linking the PetE enhancer to the transgene resulted in increased beta-glucuronidase activity and increased amounts of acetylated histones H3 and H4 present on the promoter, suggesting that the enhancer may increase transcription by mediating the acetylation of histones. Trichostatin A and sodium butyrate, which are potent inhibitors of histone deacetylases (HDAs), activated expression from the PetE promoter by fourfold, with a concomitant increase in the acetylation states of histones H3 and H4, as determined by ChIP, indicating that the acetylation of histones has a direct positive effect on transcription. The HDA inhibitors did not increase expression from the PetE promoter when it was linked to the enhancer, consistent with preexisting hyperacetylated histones on the transgene. Mapping of histone acetylation states along the reporter gene indicated that the histones H3 and H4 associated with the promoter and the 5' region of uidA were hyperacetylated in the presence of the PetE enhancer. The PetE enhancer bound to isolated tobacco nuclear matrices in vitro and was associated with the nuclear matrix in nuclei isolated from transgenic tobacco plants. These results suggest that the pea PetE enhancer activates transcription by associating with the nuclear matrix, mediating the acetylation of histones on the promoter and the nearby coding region and resulting in an altered chromatin structure.

Acetylation↗
PubMed1991

Thymic nuclear matrix associated activity is not V(D)J recombinase.

It was previously reported that nuclear matrix isolated from young rat thymus contained an activity that supported V(D)J recombination at a high efficiency (Dave et al., BIOCHEMISTRY 30: 4763-4767, 1991). A similar type of activity is also detected in the matrix prepared from fetal calf thymus. However, restriction enzyme mapping analyses of the recombined product clearly suggest that the double antibiotic resistance exhibited by the matrix treated plasmid substrate is not a consequence of V(D)J signal sequence recombination.

Animals↗
PubMed1988

Changes in structure and protein composition of bovine lymphocyte nuclear matrix during concanavalin-A-induced mitogenesis.

A major component of nuclear change in concanavalin-A-stimulated bovine lymphocytes is a severalfold increase in interchromatinic volume, which coincides with nuclear swelling and extensive structural remodelling. Large-scale ultrastructural changes in isolated nuclei and nuclear matrices (NM) reflect those occurring within nuclei in situ during mitogenesis. While nonchromatinic nuclear material embedded within nuclease- and salt-extracted whole cells closely resembled in situ interchromatinic matrices, large NM isolated in solution shrank after chromatin was extracted. Numerous perinuclear filaments persisted throughout NM isolation and cytoskeletal proteins were identified in two-dimensional (2-D) gels of such preparations. Taken together these data indicated that the lymphocyte cytoskeleton is likely continuous with the nuclear matrix and could play a role in maintaining nuclear organization. A wide range of lymphocyte NM proteins were resolved in 2-D gels. Significant changes in protein composition coincided with nuclear structural remodelling. Lamin B was prominent at each stage of nuclear development, whereas lamins A and C were only found in stimulated lymphocyte matrices. Lymphoblast NM contained more large basic proteins. Progressively increasing polypeptide complexity of these NM arose by de novo protein synthesis and posttranslational modifications throughout concanavalin A stimulation. NM from stimulated lymphocytes also contained more ribonucleoproteins, possibly indicating the presence of significant amounts of transcriptional material.

Animals↗