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Results for “Nuclear Matrix”

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PubMed1983

Processing of SV40 RNA is associated with the nuclear matrix and is not followed by the accumulation of low-molecular-weight RNA products.

Nuclear matrices from SV40-infected cells were prepared by treating purified nuclei with DNase and salt to extract DNA and histones. After a 10-min pulse with [5,6(-3)H]uridine over 85% of the viral RNA was found in association with the nuclear matrix. Following a 3-hr chase with glucosamine and unlabeled uridine, 2-4 S nuclear viral components accumulate, but they are not associated with the nuclear matrix. The 2-4 S components had been characterized previously as viral RNA processing products (N. H. Chiu, M. F. Radonovich, M. M. Thoren, and N. P. Salzman, J. Virol. 28, 590-599, 1978). The results of the present study identify the 2-4 S components as DNA rather than RNA, thus indicating that the synthesis and the majority of the processing products of the viral RNA are associated with the nuclear matrix.

Animals↗
PubMed1992

Localization of nuclear matrix core filament proteins at interphase and mitosis.

The gentle removal of chromatin uncovers a nuclear matrix consisting of two parts: a nuclear lamina connected to the intermediate filaments of the cytoskeleton and an internal matrix of thick, polymorphic fibers connecting the lamina to masses in the nuclear interior. This internal nuclear matrix can be further fractionated to uncover a highly branched network of 9 nm and 13 nm core filaments retaining some enmeshed bodies. The core filament network retains most of the nuclear RNA, as well as the fA12RNP antigen, and may be the most basic or core element of internal nuclear structure. One high molecular weight protein component of the core filament network, the H1B2 antigen, is normally masked in the interphase nucleus and is uncovered as the chromatin condenses at mitosis. This protein is associated with a fibrogranular network surrounding and connected to the chromosomes. The core filament-associated fA12 antigen also becomes associated with this perichromosomal network. We propose that the core filament nuclear matrix structure may not completely disassemble at mitosis but, rather, that parts remain as a structural network connected to chromosomes and other mitotic structures. These mitotic networks may, in turn, serve as the core structures on which the nuclear matrices of daughter cells are built.

Animals↗
PubMed1999

The nuclear matrix in pathology.

For a long time the molecular basis of nuclear structure has been a matter of debate rather than an established fact. In the last decade the concept of the nuclear matrix has emerged, and the molecular basis of this nuclear infrastructure, although still incomplete, is gradually being unravelled. In early studies concerning the nuclear structure, autoantibodies derived from patients with collagen disease had a significant role. This matrix, the structure remaining after extraction of membranes, nucleic acids and histones, consists of the nuclear lamina, the nucleolus and a fibrillogranular network. The nuclear lamina is composed of the lamins. The nucleolar matrix contains the proteins involved in rRNA processing. The fibrillogranular network is composed of nuclear matrix proteins, a wide variety of which has been discovered. It has become clear that the nuclear matrix not only provides a structural basis for nuclear architecture but also plays a part in regulating nuclear function. Lamins provide mechanical continuity between cytoskeleton and nuclear interior. Aberrant patterns of lamin expression have been described in cancer; these are not sufficiently specific to be used in histopathological diagnosis, however. Nucleolar size and expression levels of nucleolar proteins have been shown to correlate well with proliferative activity, which may revitalize interest in nucleolar organizing regions as a tool in histological diagnosis of cancer. The fibrillogranular network is involved in functional compartmentalization of replication and transcription. A variety of nuclear matrix proteins has been described, which appear to be specifically expressed in cancer cells. Analysis of expression of these proteins might play a significant role in cancer diagnosis.

Animals↗
PubMed1999

Nuclear shape and nuclear matrix protein composition in prostate and seminal vesicles.

OBJECTIVES: The nucleus controls cell function and behavior. The nuclear matrix determines internal nuclear changes. Two-dimensional gel electrophoresis is the reference standard for the analysis of nuclear matrix protein (NMP) composition. Differences in NMP composition should therefore be reflected by changes in nuclear shape. We investigated the differences in NMP composition and nuclear morphometry of the prostate and seminal vesicles. Both tissues are androgen-dependent sex accessory organs with completely different biologic behavior. METHODS: High-resolution two-dimensional gel electrophoresis and silver staining were used to evaluate NMP composition from histologically normal prostate and seminal vesicle epithelial cells. Nuclear morphometry, performed using a computer-assisted image analysis system, described the distribution, variability, and extremes of nuclear shape. RESULTS: NMP composition analysis demonstrated that both tissues have a similar NMP composition, and tissue-specific NMPs that were consistently present in all specimens of each tissue could not be demonstrated. Nuclear morphometry showed a significantly greater heterogeneity in nuclear shape in the seminal vesicles than in the prostate. CONCLUSIONS: The striking similarity of the NMP composition demonstrates the close biologic relationship between prostate and seminal vesicle tissue. The similar NMP composition does not correlate with the marked alterations in nuclear shape and structure between these tissues. Therefore, nuclear morphometry may depict differences in the functional state of a similar set of NMPs, shown by two-dimensional gel electrophoresis, which may be responsible for the different biologic behavior of these tissues.

Antigens, Nuclear↗
PubMed1995

Inhibition of the association with nuclear matrix of pRB, p70 and p40 proteins along with the specific suppression of c-MYC expression by geldanamycin, an inhibitor of Src tyrosine kinase.

Geldanamycin is an antibiotic that preferentially inhibits G1/S transition and causes G2/M arrest in human leukemia HL-60 cells. With it, we selectively inhibited recombinant Src tyrosine kinase without significantly inhibiting protein kinase A. The perturbation of cell cycling by geldanamycin was accompanied by marked suppression of c-MYC expression. In contrast to this, pRB expression was remarkably enhanced by geldanamycin. In the untreated HL-60 cells, c-MYC was apparently enriched in nuclear matrix preparation, and significant amounts of hyperphosphorylated pRB, p70 and p40 proteins were observed to associated with the nuclear matrix. The amounts of these proteins associated with the nuclear matrix, however, were markedly decreased by treatment with geldanamycin. This finding suggests that the association of c-MYC, hyperphosphorylated pRB, p70 and p40 proteins with the nuclear matrix is essential in cell cycling, especially in G1/S and G2/M progressions, and that this association is a part of signal transduction pathway in Src kinase activation.

Antibiotics, Antineoplastic↗
PubMedDate not supplied

[Proteins of the nuclear matrix and their phosphorylation in normal and tumor cells].

The protein composition of the nuclear matrix of normal and tumor cells is discussed. A characteristic feature of the latter is the predominance of high molecular weight polypeptides containing mainly glyco- and phosphoproteins. Only few of them are identified. Nuclear matrix preparations from tumors differ by the presence of fibronectin and phosphotyrosine-containing proteins with a molecular mass of nearly 180 and 170 kDa as well as of high turnover of high molecular weight protein group and inhibition of their biosynthesis by chloramphenicol.

Animals↗
PubMedDate not supplied

[Proteins bound to satellite DNA, are present in human nuclear matrix cell preparations].

The presence of protein or complex of proteins that specifically bind to human satellite 3 (HS3) was shown during investigations of the nuclear matrix. The specificity of binding of HS3 was shown by using nuclear matrix immobilized on nitrocellulose. The activity disappeared after extractions of the nuclear matrix. The presence of specific activity in low salt extract was shown by gel retardation assay with whole HS3 fragment. All the subfragments of HS3 after Sau3A restriction (1 kb, 0.36 kb, 0.41 kb) also retarded in the mixture with this protein extract. DNA-protein complexes were stable even in the presence of a 1000-fold excess of competitive DNA. These data are discussed in the frame of hypotheses about the three dimensional organization of interphase chromatin.

Autoradiography↗
PubMed1988

Androgen-dependent nuclear proteins in rat ventral prostate are glycoproteins associated with the nuclear matrix.

The major rat ventral prostate androgen-dependent nuclear proteins were studied using isolated nuclei, nuclear matrix and nuclear envelope fractions. Nuclear and subnuclear fractions obtained were characterized by electron microscopy and SDS-polyacrylamide gel electrophoresis. A group of approximately 20 kDa peptides is demonstrated to be present in nuclei, nuclear matrices and nuclear envelopes from normal prostate. Time course experiments indicate that the 20 kDa peptides become drastically reduced after 7 or 10 days following castration and are incompletely restored after 3 daily testosterone injections. Lectin binding studies demonstrate that the 20 kDa peptides bind both to Concanavalin A and Wheat Germ Agglutinin. These peptides represent the major nuclear Concanavalin A binding glycoproteins from normal prostate nuclei and nuclear matrices.

Androgens↗
PubMed2001

Human papillomavirus 16 E6 is associated with the nuclear matrix of esophageal carcinoma cells.

AIM: To explore the etiologic role of HPV infection in esophageal carcinoma, and the association of HPV-16 E6 with the nuclear matrix of carcinoma cells. METHODS: Two esophageal carcinoma cell lines,EC/CUHK1 and EC/CUHK2, were tested for HPV-16 E6 subgenetic fragment by polymerase chain reaction amplification of virus DNA associated nuclear matrix. RT-PCR and immunocytochemistry were also used to visualize the expression of E6 subgene in the cells. RESULTS: The HPV-16 E6 subgenetic fragment was found to be present in nuclear matrix-associated DNA, E6 oncoprotein localized in the nucleus where it is tightly associated with nuclear matrix after sequential extraction in EC/CUHK2 cells. It was not detected, however, in EC/CUHK1 cells. CONCLUSION: The interaction between HPV-16 E6 and nuclear matrix may contribute to the virus induced carcinogenesis in esophageal carcinoma.

Antigens, Nuclear↗
PubMed1993

On the association of DNA primase activity with the nuclear matrix in HeLa S3 cells.

We have reinvestigated the association of DNA primase activity with the nuclear matrix prepared from exponentially growing HeLa S3 cells. We have found that 25-30 per cent of the nuclear primase activity resists extraction with 2 M NaCl and digestion with Dnase I. Unlike previous investigations, done with the same cell line, the results showed that nuclear matrix-bound DNA primase activity represented less than 10 per cent of the total cell activity. Association of high levels of primase activity with the nuclear matrix was strictly dependent on a 37 degrees C incubation of isolated nuclei prior to subfractionation. Evidence was obtained that the method used for preparing nuclei can have a dramatic effect on the amount of primase activity which is recovered both in the postnuclear supernatant and in isolated nuclei, thus seriously affecting the interpretation of the results about the quantity of DNA primase activity bound to the nuclear matrix.

Cell Compartmentation↗
PubMed1989

Microtubule-associated protein-2 stimulates DNA synthesis catalyzed by the nuclear matrix.

Microtubule-associated protein-2 (MAP-2) isolated from porcine brains stimulated DNA synthesis catalyzed by the nuclear matrix isolated from Physarum polycephalum in the presence of activated DNA as exogenous templates. The degree of the stimulation depended on the amount of the nuclear matrix, but not on that of the template. MAP-2 also stimulated DNA polymerase alpha activity solubilized from nuclei, but not DNA polymerase beta activity. These results suggest that MAP-2 stimulates DNA synthesis by interacting with the putative DNA replication machinery including DNA polymerase alpha bound to the matrix. Similar stimulation occurred in the nuclear matrix isolated from HeLa and rat ascites hepatoma cells, which strongly suggests that MAP-2 is involved in the control of DNA replication in eukaryotic cells.

Animals↗
PubMed1986

Protein composition of nuclear matrix preparations from HeLa cells: an immunochemical approach.

Procedures for the isolation of HeLa S3 nuclear matrices were re-examined with special emphasis on the use of various nucleases and detergents as well as on the ionic strength of the final salt extraction. The protein composition of the resulting nuclear matrix preparations was analysed by one- and two-dimensional gel electrophoresis and found to be extremely reproducible. By means of co-electrophoresis several typical cytoskeletal proteins (actin, vimentin and cytokeratins) and heterogeneous nuclear RNA (hnRNA)-associated core proteins (hnRNP) were shown to be present in such nuclear matrix preparations. The nature of some other protein components was elucidated using two-dimensional immunoblotting and immunofluorescence. For this purpose mouse monoclonal antibodies to cytoskeletal components (vimentin, cytokeratins), small nuclear RNP (70 X 10(3) Mr protein of U1-RNP), hnRNP (C1/C2) and the pore-complex lamina (lamins A, B and C) were used next to human autoimmune sera obtained from patients with connective tissue diseases and directed against the residual nucleoli and the internal fibrillar mass. These antibodies enabled us to identify a number of proteins present specifically in the nuclear matrix and to show that part of the cytoskeletal proteins are still present in the isolated structures.

Cell Nucleus↗
PubMed1991

A comprehensive study on the isolation and characterization of the HeLa S3 nuclear matrix.

Different agents have been employed to extract the histones and other soluble components from isolated HeLa S3 nuclei during nuclear matrix isolation. We report that 0.2M (NH4)2SO4 is a milder extracting agent than NaCl and LIS (lithium 3,5-diiodosalicylate), on the basis of the apparent preservation of the elaborate fibrogranular network and the residual nucleolus that resemble the in situ structures in whole cells and nuclei, minimal aggregation, and sufficient solubilization of DNA and histones. The importance of intermolecular disulfide bonds, RNA and 37 degrees C stabilization on the structural integrity of the nuclear matrix was examined in detail using sulfydryl alkylating, reducing and oxidizing agents, and RNase A. The data suggest that any disulfides formed during the isolation are not essential for maintaining the structural integrity of the in vitro matrix. However, structural integrity of the matrix is dependent upon RNA and to some degree on disulfides that presumably existed in situ. Sodium tetrathionate and 37 degrees C stabilization of isolated nuclei resulted in nuclear matrices containing an approximately twofold greater amount of protein, RNA and DNA than control preparations. The 37 degrees C incubation, unlike the sodium tetrathionate stabilization, does not appear to induce intermolecular disulfide bond formation. Neither stabilizations resulted in significant differences of the major matrix polypeptide pattern on two-dimensional (2-D) gels stained with Coomassie Blue as compared to that of unstabilized matrix. The major nuclear matrix proteins, other than the lamins, did not react to the Pruss murine monoclonal antibody (IFA) that recognizes all known intermediate filament proteins, suggesting that the internal matrix proteins are not related to the lamins in intermediate filament-like quality.

Blotting, Western↗
PubMed2000

Detection of lectins in the nuclear matrix of nerve tissue cells.

Lectins have been detected in the nuclear matrix of nerve tissue cells, and an extraction procedure for the protein fraction with lectin activity has been developed. The lectins are characterized by hemagglutinating activity that is inhibited by D-GlcNAc, D-Gal, Lac, and D-Glc. The existence of lectins with similar molecular masses (from 7 to 20 kD) in the nuclear matrix of calf and rat brain has been shown.

Animals↗
PubMed1983

Specific DNA sequences associated with the nuclear matrix in synchronized mouse 3T3 cells.

Eukaryotic chromatin appears to be organized into arrays of supercoiled loops anchored to the scaffolding structure of the mitotic chromosome core or to the nuclear matrix of interphase nuclei. To reveal whether specific DNA sequences are involved in this level of chromatin organization, we isolated and cloned a population of DNA molecules [average length of 150 base pairs (bp)] closely associated with the nuclear matrix after exhaustive DNase digestion and subsequent extensive protease digestion. The nuclear matrix was obtained from murine BALB/c 3T3 cells synchronized at the G1/S border of the cell cycle. We report the structure of two sequences, designated G4 and G5, which are highly enriched in the matrix DNA. Sequence G4, of 152 bp, contains three 31-bp direct head-to-tail repeats. An 11-bp sequence at the end of each repeat is homologous to the first large tumor antigen recognition site of human papova virus. Sequence G5, of 135 bp, consists of two well-defined domains, in which the first domain is a fragment of the B1 repetitive sequence. The results suggest the possibility that the loops of histone-depleted chromatin are connected to the scaffold of the nuclear matrix, with specific DNA sequences at the anchorage sites.

Animals↗
PubMed1998

Comparison of nuclear matrix proteins between EGFR-antisense transfected and untransfected glioblastoma cells.

The protein composition of the nuclear matrix is both tissue and cell type specific, and it undergoes changes with differentiation and transformation. In the present study, nuclear matrix proteins of EGFR-antisense transfected glioblastoma cell lines, U87 and U343, were compared with untransfected cell lines using two dimensional-gel electrophoresis. After EGFR-antisense transfection, the protein compositions of the nuclear matrices in both cell lines were different. Several nuclear proteins were only found in EGFR-antisense transfected cell lines. There was no difference in NuMA expression in the transfected and untransfected cell lines. These results suggest that EGFR-antisense reduced tumorigenicity on human glioblastoma cells by changing nuclear matrix protein compositions.

Journal Article↗
PubMed1985

Specific binding of 3H-estradiol to rat prostate nuclear matrix.

Specific estradiol binding activities can be demonstrated in nuclear matrix preparations obtained from intact rat prostate nuclei. Some of the characteristics of these in vitro binding activities to intranuclear components are presented and compared to those exhibited by purified nuclear fractions. Examination of the effects of exposure to castration and testosterone on the number of nuclear matrix binding sites revealed that the quantity and quality (Type) of receptors was modified. Furthermore, these changes are prevented when protein synthesis was inhibited.

Animals↗
PubMed1987

Pre-replicative association of multiple replicative enzyme activities with the nuclear matrix during rat liver regeneration.

As a step toward the molecular elucidation of the putative replicational apparatus associated with the nuclear matrix, we have investigated the possible matrix association of several replicational related enzymes. In addition to the previously identified DNA polymerase alpha, DNA primase, 3'-5' exonuclease, RNase H, and DNA methylase were all recovered at significant levels (20-30% of total nuclear activity) in nuclear matrix isolated from regenerating rat liver during maximal in vivo replication (22 h post-hepatectomy). In contrast, DNA ligase was not detected on the nuclear matrix even though significant activity was present in isolated nuclei. Examination of the replicative dependency of these enzyme activities following partial hepatectomy revealed pre-replicative elevations which were distinct for each matrix-bound enzyme. A second late-replicative peak in DNA methylase is consistent with a role of this matrix-bound enzyme in the maintenance of the inheritable methylation pattern. Mild sonication resulted in a significant release of all of these activities except RNase H. A major portion of the matrix-solubilized DNA polymerase alpha, DNA primase, 3'-5' exonuclease, and DNA methylase activities cosedimented on sucrose gradients between approximately 8-12 S. Our results are consistent with the organization of at least a portion of these replicative enzymes into nuclear matrix-bound replicational complexes. We also propose a novel pre-replicative assembly model of the matrix-bound replicational apparatus in which DNA primase plays an initial and critical role.

Animals↗