Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Complete suppression of polyadenylation of nuclear precursors of rat brain mRNA by cordycepin leads to degradation of some translatable sequences of both poly(A)(+)- and poly(A)- pre-mRNA localized in 80S hnRNP-particles. This fact has been established by comparative analysis of the data of two-dimensional gel-electrophoretic mapping of translation products synthesized in reticulocytic cell-free system using the exogenous purified templates of rapidly labelling translatable 9-17S hn RNA (pre-mRNA) isolated from brain 80S hn RNP particles of experimental (4 hrs after cordycepin injection) and control (injection of physiological solution) adult healthy male rats. Long contact of brain cells with cordycepin (4 or more hrs) creates conditions for formation of hnRNP-particles devoid of poly(A)+ RNA and poly(A)-binding proteins. These particles differ from "normal" ones by the value of the RNA/protein ratio, and by considerably lower resistance to the action of exogenous ribonucleases and endogenous RNase. Cordycepin does not have a direct effect on biosynthesis of nuclear poly(A)-binding proteins within the duration of the experiment (8 hrs). The phenomena described are discussed.
...
PMID:The molecular mode of brain mRNA processing damage followed by the suppression of post-transcriptional poly(A) synthesis with cordycepin. 226 8

When fixed newt lampbrush chromosomes are treated with RNase to remove nascent transcripts and are then probed with radiolabeled single-stranded DNA in 0.1 x SSC, proteins associated with the majority of the lateral loops bind the probe nonspecifically. One or more common hnRNP proteins, several of which are known to bind single-stranded DNA, could be responsible for this generalized binding. In 1.0 x SSC only a relatively small subset of loops continues to bind the probe. In order to characterize this subset of loops, we prepared polyclonal antibodies against DNA-binding proteins initially identified by "Southwestern" analysis. We show by an in situ double labeling experiment that a polyclonal serum raised against gel-eluted histone H1 recognizes the same lateral loops that bind DNA in 1.0 x SSC.
...
PMID:DNA-binding proteins on lampbrush chromosome loops. 248 28

A heterogeneous RNP structure has been isolated from rat liver nuclei by a method previously used for the isolation of 30S RNP complexes carrying heterogeneous RNA (hnRNA) [1]. The RNP sediments in sucrose gradients with s-values of 70-110S. Formaldehyde-fixed preparations band at Q = 1.40 in isopycnic CsCl gradients. The RNP structure is composed of a heterogeneous population of polypeptides, prominent among which are two proteins with Mr 74000 and 72000. It contains both rapidly labelled RNA as well as several species of snRNA, as demonstrated by double-labelling experiments and gel electrophoresis. Treatment of rats with alpha-amanitin leads to a significant decrease in the amount of recovered RNP. In the presence of 0.7 M NaCl the s-value of the complex changes from 70-110S to 40-80S. The RNP structure is stable to mild RNase A or micrococcal nuclease digestion. Transmission electron microscopy reveals the presence of a heterogeneous population of particles with a mean diameter of 300-360 A. The isolated RNP structure differs completely from the well-known monoparticle or polyparticle hnRNP complexes and from the 30S or smaller snRNP particles but could be similar to or identical with the heterogeneous complex described by Jacob et al. [29].
...
PMID:Isolation and characterization of nuclear particles containing rapidly labelled hnRNA and snRNA in combination with a distinct set of polypeptides of Mr 74000 and 72000. 257 70

The organization of select proteins within ribonucleoprotein particles containing heterogeneous nuclear and uridine-rich small nuclear RNAs (hnRNP and UsnRNP respectively) was examined by chemical cross-linking and ribonuclease digestion using diagonal two dimensional PAGE and immunoblotting detection systems. Monoclonal antibodies specific for A2, C1 and C2 hnRNP proteins, detected these proteins at gel coordinates which suggested homotypic dimers and trimers of A2 and homotypic trimers, hexamers and larger multimers of C1 and C2. Ribonuclease digestion did not alter the cross-linking properties of hnRNP C1 and C2 proteins but did result in loss of A2 homotypic dimers and trimers. Blots simultaneously reacted with hnRNP specific monoclonal antibodies and autoimmune patient serum (RNP/Sm), or monoclonal antibodies reactive with the U1 snRNP specific 63 kDa protein and/or the UsnRNP common proteins B', B and D revealed no complexes which would indicate interactions between hnRNPs and UsnRNPs. The U1 UsnRNP specific 63 kDa protein appeared not to be cross-linked to UsnRNP common B', B and D proteins. The data also suggested that UsnRNP common protein D was cross-linkable to UsnRNP common proteins D', E and G but not to B' and B. The cross-linking properties of D were unaffected by ribonuclease digestion. In contrast, ribonuclease digestion resulted in an inability to cross-link select complexes containing either B' and B, or p63. The data suggest that both hnRNPs and UsnRNPs are comprised of RNA-dependent and RNA-independent protein-protein interactions.
...
PMID:Reversible chemical cross-linking and ribonuclease digestion analysis of the organization of proteins in ribonucleoprotein particles. 323 Dec 14

A monoclonal antibody obtained after mice were immunized with hnRNP purified from HeLa cells recognizes two polypeptides of Mr 35,000 and 37,000. By immunocytofluorescence, these antigens can be visualized only in cells previously heat shocked at 45 degrees C for 5 or 10 min, although they are present at the same level in unstressed and stressed cells. The signal, which is mostly concentrated in the interchromatin space, where hnRNP fibrils are located, does not accumulate with time and disappears 4 to 5 h after heat shock. Discrimination between the two types of hnRNP substructures, the 30-50 S monoparticles and the nuclear matrix fibrils, based on differential sensitivity to salt or ribonuclease treatment, showed that in unstressed cells the antigens behave as monoparticle proteins. In contrast, in heat-shocked cells, most 35-37K antigens behave as nuclear matrix proteins. Thus, heat shock seems to induce a rapid and reversible switch of these two antigens from hnRNP monoparticles to the nuclear matrix. The data demonstrate that heat shock, which was previously shown not to alter the overall RNA: protein packaging ratio of hnRNP, induces subtle modifications of their substructure. Such modifications might be of importance since heat shock is known for instance to affect pre-mRNA processing.
...
PMID:The distribution of two hnRNP-associated proteins defined by a monoclonal antibody is altered in heat-shocked HeLa cells. 327 13

Heteronuclear RNA (hnRNA) is preferentially associated (76%) with the nuclear matrix in mammalian cells. Active mRNA, in the form of polyribosomes, is associated (greater than 97%) with the cytoskeletal framework. In this report, we present evidence that the association of both hnRNA and mRNA with structural networks of the cell may be essential features of gene expression. To study the association of polyribosomes with the cytoskeletal framework, cytochalasin D was used to release mRNA from the cytoskeletal framework. Protein synthesis was inhibited by cytochalasin D in direct proportion to the release of mRNA. The released mRNA is unaltered in its translatability as measured in vitro but is no longer translated in the cytochalasin-treated HeLa cells. The residual protein synthesis occurs on polyribosomes that are reduced in amount but display a normal sedimentation distribution. The results support the hypothesis that mRNA binding to the cytoskeletal framework is necessary, though not sufficient, for translation. Further fractionation of the cytoskeletal framework separates nuclear constituents into three distinct protein fractions. Chromatin proteins and 94% of the DNA are released by 0.25 M-ammonium sulphate after inter-nucleosomal DNA is cut with DNase I. The resulting structure retains 76% of the hnRNA in the form of ribonucleoprotein and is designated the RNP-containing nuclear matrix. The proteins of hnRNP complex are those associated with the nucleus only if RNA is intact. These proteins and 97% of the hnRNA are released after brief digestion with RNase A. Visualizing the nuclear matrix using resinless sections shows that nuclear RNA plays an important role in the organization of the nuclear matrix. Electron micrographs of resinless sections show the interior of the matrix to be a three-dimensional network of thick filaments bounded by the nuclear lamina. The filaments are densely covered with 20-30 nm electron-dense particles, which may contain the hnRNA. The RNP-depleted matrix is disordered and the interior fibres aggregated. These results suggest that hnRNA is involved in the spatial organization of the interior of the nuclear matrix.
...
PMID:Association of RNA with the cytoskeleton and the nuclear matrix. 347 58

The present report describes the isolation of hnRNP complexes with sedimentation coefficients greater than 80 S from rat liver nuclei without the use of ribonuclease inhibitors. The RNA moiety from these complexes is heterogeneous in size, with a mean sedimentation coefficient of 16 S when assayed with polyacrylamide-formamide gel electrophoresis. About 3% of this RNA binds to oligo(dT)-cellulose, the size of the bound fraction being somewhat smaller than the bulk of the hnRNP-RNA. This poly(A) RNA contains two adenylate tracts, one with about 30 and the second with about 200 adenylate residues. Reverse transcription of the poly(A)-containing RNA and hybridization of the cDNA with their respective templates shows two well-defined frequency populations, the first one separated from the second by almost 2.5 logs in the R0t curve. The same distribution was found, whether the hybrids were analysed with S1 nuclease or hydroxyapatite. Both separated frequency classes hybridize to total genomic DNA, the abundant one at C0t values typical for repetitive and unique sequences, the scarce one only at C0t values typical for unique sequences. The two populations are also able to hybridize with polysomal polyadenylated mRNA, the dilution of both frequencies being very similar in the cytoplasm.
...
PMID:Poly(A)- and oligo(A)-adjacent sequences in RNA from the large hnRNP complexes of rat liver. 616 64

Of the RNA labelled after incubation of hepatoma cells with radioactive precursors for 20 and 150 min. 35% and 70%, respectively, can be isolated from nuclei by two consecutive extractions with 0.14 M NaCl at pH 8. The isolated RNA is complexed with nuclear proteins forming structures with sedimentation coefficients of less than 30 S to greater than 100 S. Similar complexes from rat liver isolated under the same experimental conditions show coefficients of 30-40 S. The RNA-associated proteins are similar, on the basis of sodium dodecyl sulphate/polyacrylamide gel electrophoresis, to the respective proteins of other cell types. The presence on these RNP complexes of six discrete small nuclear RNAs (snRNA) has been established. Experiments with a reversible inhibitor of RNA synthesis, D-galactosamine, demonstrated, differences in the turnover of hnRNA and snRNA. The half-lives of the six snRNA species has been determined, varying from 32 h for snRNA species a, b and d, to 22 h for snRNA species e and f and to 13 h for snRNA species c. Treatment of the nuclear extracts with 0.7 M and 1 M NaCl results in dissociation of hnRNA from the 'core' and other polypeptides, whereas snRNA remains complexed with polypeptides of Mr 54 000-59 000. Incubation of the nuclear extracts at 0 C with low doses of pancreatic R Nase (up to 1.5 micrograms/ml), which renders approximately 80% of the hnRNA acid-soluble and cleaves most of the snRNA, results in conversion of the high-molecular-weight hnRNPs to 30-S structures, without disrupting the 30-S RNP. Treatment of the nuclear extracts with higher doses of RNase (3 micrograms/ml) leads to disruption of the 30-S RNP and release of the hnRNA-associated proteins, underlining the importance of hnRNA-protein interaction for the retainment of the hnRNP structures.
...
PMID:Isolation and characterization of hnRNA-snRNA-protein complexes from Morris hepatoma cells. 618 25

Chromatin-depleted nuclei (CDN) were prepared from Friend erythroleukemia cell nuclei by partial digestion with DNase I and extraction of the chromatin by 2 mM EDTA as described in the preceding paper (Long and Ochs, 1983. Biol. Cell 48, 99-108). These structures contained dense networks of matrix fibrils surrounded by distinct laminae but no morphologically distinct residual nucleoli. CDN disrupted by gentle shearing or 1 microgram/ml RNase were fractionated into laminae and matrix fibrils by differential centrifugation. Protein composition of the lamina fraction was dominated by two prominent lamina proteins that were not detectable in the matrix fraction. Mild RNase treatment led to a conversion of the fibrous network to a particulate morphology while mild shearing resulted in an apparently unaltered fibril fraction. The matrix fibril fractions contained hnRNP proteins and the snRNAs. These results suggest that EDTA-prepared CDN may provide a system for studying snRNP-hnRNP interactions and hnRNP processing that is less complex than intact nuclei.
...
PMID:Isolation from Friend erythroleukemia cells of an RNase-sensitive nuclear matrix fibril fraction containing hnRNA and snRNA. 620 Dec 19

Nonhistone proteins (NHPs) of salt-soluble chromatin (Chromatin S) and of the residual nuclei (Chromatin P) from rat liver and thymus were studied by SDS-polyacrylamide gel electrophoresis. The two chromatin fractions of the liver showed significant differences in their NHP patterns with most of the hnRNP and matrix proteins occurring in Chromatin P. In accordance with the low protein content of thymus nuclei, the corresponding thymus fractions exhibited electrophoretic patterns with a markedly lower amount of NHPs than in liver. Chromatin P from thymus, in contrast to the liver fraction, revealed only a very low content of hnRNP-specific proteins of molecular weight 30,000-40,000 (30 K to 40 K) (informosomal proteins) consistent with the significantly lower RNA content of thymus nuclei. In the region of the matrix proteins (60-75 K) Chromatin P showed only two bands of about 64 K and 73 K in thymus, whereas in liver five strong bands at 64 K, 66 K, 69 K, 73 K, and 75 K were found. RNase digestion was employed to discriminate hnRNP-specific protein from "real" chromosomal NHPs. At least about 65% and 25% of the NHPs from Chromatin P and S of liver, respectively, were found to be RNP-specific. The two chromatin fractions were further fractionated by sucrose gradient centrifugation and isopycnic banding in metrizamide. After centrifugation the main peaks, both of Chromatin S and P, contained only minor amounts of NHPs with a predominating protein of 38 K. By the centrifugation procedures described in this paper, a small subfraction of chromatin could be separated which was enriched in newly synthesized RNA, informosomal proteins, matrix- and other high molecular weight proteins. This subfraction might be related to transcriptionally active chromatin.
...
PMID:Discrimination of several classes of nonhistone proteins in chromatin fractions from liver and thymus nuclei of rats. 714 70


1 2 3 Next >>

---