Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.5 (RNase)
 17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A heat-labile, non-dialyzable factor(s) in soluble fractions from porcine, bull, rabbit and cock spermatozoa was found to incorporate the radioactivity of [14C]isoleucine into a 95 degrees C CCl3COOH-insoluble fraction. The incorporation required ATP, Mg2+, casein and 2-mercaptoethanol. Trypsin and alpha-chymotrypsin inhibited the incorporation, while RNase A and DNase I did not. A mixture of 19 amino acids other than isoleucine had no effect on the incorporation. The reaction product was identified as protein. The incorporated moiety was the isoleucyl moiety of isoleucine and it retained a free alpha-amino group in the product protein. Some other characteristics of this incorporation are also described.
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PMID:Incorporation of isoleucine into protein by a soluble fraction from spermatozoa. 398 5

The ultrastructure and the polypeptide composition of residual nuclear substructures including nuclear matrices, nuclear ghosts, and residual envelopes were investigated by means of electron microscopy and two-dimensional gel electrophoresis. Nuclear matrices were prepared by digesting isolated nuclei with DNase I alone, followed by high-salt extraction in 2 M NaCl. Nuclear ghosts were obtained by high-salt extraction of nuclei previously digested with DNase and RNase in MgCl2-containing buffers. To prepare residual envelopes, nuclei were first digested with RNase in the presence of EDTA, then digested with Mg2+ -activated DNase I, and extracted in 2 M NaCl. The results of this comparative study support the conclusion that the intranuclear matrix is made of two distinct RNA-containing elements. One of these elements appears on ultrathin sections as a thin fibrillar network. It disappears from RNase-digested nuclei, together with numerous basic proteins, whatever the conditions of digestion. Although this element is present in extranucleolar territories, it is a major component of residual nucleoli. The second element appears as coarse-beaded fibers absent from the nucleolar areas. Its preservation in residual nuclear substructures depends on the presence of Mg2+ ions during RNase digestion of nuclei. It is enriched in two minor basic proteins of relative mass 49 000 and 70 000. The involvement of this fibrogranular element in heterogeneous nuclear RNA attachment to the nuclear matrix is discussed.
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PMID:Nuclear RNA-associated proteins and their relationship to the nuclear matrix and related structures in HeLa cells. 404 64

When rat liver nuclear chromatin was sonicated in buffer containing 0.35 M (NH4)2SO4 to release the engaged RNA polymerases, a potent inhibitor was also released. This inhibitor elicited dramatic inhibition of RNA synthesis regardless of whether the free or engaged RNA polymerase was used. On further analysis, it became apparent that the site of inhibition was on the DNA template, not on the enzyme. This inhibitor could be extracted into 0.25 N HCl by the standard procedure for the isolation of histones. This acid-soluble inhibitor, showing typical histone band on gel, was RNase A and DNase I resistant, but was sensitive to both pronase and snake venom phosphodiesterase digestion, as well as to 0.1 N KOH hydrolysis. Furthermore, when [14C]adenine labeled poly-ADP-ribosylated histones were digested by snake venom phosphodiesterase, the release of radioactivity was in parallel to the loss of inhibitor activity. We conclude that the inhibitor substances are poly-ADP-ribosylated histones and propose that the poly-ADP-ribosylated histones rather than the histones are the natural suppressors of the gene.
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PMID:Poly-ADP-ribosylated histones: potent DNA suppressors. 404 88

A macromolecule binding 3H-methylcholanthrene (3H-MCA) and 3H-benzo(a)pyrene (3H-BaP) and sedimenting in the 4-5 S region of sucrose gradient (4.5 S) was identified in rat liver cytosol. The binding was displaced by 100-fold molar excess unlabeled ligands whereas 2,3,7,8-tetrachloro-dibenzo-p-dioxin (TCDD) was ineffective. The dissociation constant for both polycyclic aromatic hydrocarbons (PAHs) was of the order of 10(-8) M or lower. Both 3H-MCA and 3H-BaP bound to 4.5 S in a non covalent manner, since 92% of the bound radioactivity was extractable with ethyl ether. Furthermore the binding was strongly reduced by urea 8 M and by guanidine. HCl 4 M (99 and 70% respectively). Thin layer chromatography of the ethyl ether-solubilized radioactivity showed a peak comigrating with PAHs used as standards. When chromatographed on Sephadex G-200, 4.5 S was eluted as a sharp peak with an apparent molecular weight of 50-60,000 daltons. Enzyme treatment of liver cytosol showed that the 4.5 S binding sites were destroyed by micrococcal nuclease (92% of inhibition). Papain and phosphodiesterase I and II reduced the binding to 50%, whereas DNase I, DNase II, RNase, phospholipase A2 and C and trypsin were ineffective. These data suggest that the PAHs binding macromolecule of rat liver cytosol is a protein associated with a polynucleotide. The binding of both PAHs was enhanced by increasing the incubation temperature, the maximum being reached after 20-30 min at 37 degrees C. After 2.5 min at 65 degrees C, binding sites were completely destroyed. The same temperature-induced "activation" was obtained also by prewarming the cytosol at 37 degrees C in the absence of ligands.
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PMID:Polycyclic aromatic hydrocarbon binding macromolecules. Identification, characterization and temperature activation of a 4.5 S binding nucleoprotein. 406 Feb 44

A POLYRIBOADENYLATE [POLY(A)] POLYMERASE, PURIFIED FROM VACCINIA VIRUS CORES, WAS STIMULATED BY POLYDEOXYRIBOADENYLATE: polydeoxyribothymidylate [poly(dA:dT)] and by polyribocytidylate [poly(C)] primers suggesting mechanisms of either transcription or terminal addition. Evidence for the latter was obtained by the demonstration of covalent linkages between the poly(A) products and both primers. In 99% dimethylsulfoxide-sucrose gradients, the sedimentation of poly(A) formed with poly(dA: dT) primer was reduced after DNase I treatment and the sedimentation of poly(A) formed with poly(C) primer was reduced by RNase A treatment, whereas the sedimentation of poly(A) formed without primer was not affected by either. Formation of a phosphodiester bond between primer and product was demonstrated by means of isotope transfer experiments. (32)P from alpha-[(32)P]ATP was transferred to 2'(3')-CMP after alkaline or enzymatic hydrolysis of the poly(C)-primed polymerase reaction product. Transfer primarily or exclusively to 3'-dTMP was found after enzymatic hydrolysis of the poly(dA: dT)-primed polymerase reaction product. The elution pattern of the poly(A) polymerase from DNA-cellulose suggested that a single enzyme catalyzes the attachment of adenylate residues to both polyribonucleotide and polydeoxyribonucleotide primers; nevertheless the purest enzyme preparations contain two bands resolved by polyacrylamide gel electrophoresis in sodium dodecyl sulfate.
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PMID:Vaccinia virus polyriboadenylate polymerase: convalent linkage of the product with polyribonucleotide and polydeoxyribonucleotide primers. 483 99

In an earlier report, it was shown that aflatoxin B1 treatment strongly inhibits rat liver nucleolar RNA synthesis (Yu, F. L. (1977) J. Biol. Chem. 252, 3245-3251). The present paper is an attempt to elucidate the mechanism of this inhibition. Two h after aflatoxin B1 injection (0.3 mg/100 g body weight), rat liver nucleolar RNA synthesis, in vitro, was inhibited by an average of 90%. This inhibition could result from (a) inhibited RNA polymerase I activity per se, (b) impaired nucleolar DNA template, or (c) impaired nucleolar chromatin. Earlier studies found that the total RNA polymerase I activity was not affected by aflatoxin B1 treatment. In the present work the total nucleolar DNAs from control and from aflatoxin B1-treated groups were isolated and compared for template efficiencies in directing RNA synthesis with solubilized RNA polymerase I from the control group. No difference was found. However, when nucleolar chromatin function was analyzed, it was found that aflatoxin B1 treatment resulted in a dramatic reduction in the RNA chain elongation rate to only 13% of the control. The chain number, which is a measure of the number of engaged enzymes transcribing the nucleolar chromatin initiated in vivo, was only slightly reduced (33%). Furthermore since it was found that aflatoxin B1 treatment did not increase RNase activity in the treated nucleoli, the dramatic decrease in RNA chain elongation is therefore believed to be the major mechanism of aflatoxin B1 inhibition of rat liver nucleolar RNA synthesis. DNase I digestion of the nucleolar chromatin suggests that aflatoxin B1 treatment may have altered the conformation of the transcriptionally active regions of the nucleolar chromatin.
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PMID:Studies on the mechanism of aflatoxin B1 inhibition of rat liver nucleolar RNA synthesis. 616 44

The amplified, extrachromosomal nucleoli of Xenopus oocytes contain a meshwork of approximately 4-nm-thick filaments, which are densely coiled into higher-order fibrils of diameter 30-40 nm and are resistant to treatment with high- and low-salt concentrations, nucleases (DNase I, pancreatic RNase, micrococcal nuclease), sulfhydryl agents, and various nonionic detergents. This filamentous "skeleton" has been prepared from manually isolated nuclear contents and nucleoli as well as from nucleoli isolated by fluorescence-activated particle sorting. The nucleolar skeletons are observed in light and electron microscopy and are characterized by ravels of filaments that are especially densely packed in the nucleolar cortex. DNA as well as RNA are not constituents of this structure, and precursors to ribosomal RNAs are completely removed from the extraction-resistant filaments by treatment with high-salt buffer or RNase. Fractions of isolated nucleolar skeletons show specific enrichment of an acidic major protein of 145,000 mol wt and an apparent pI value of approximately 6.15, accompanied in some preparations by various amounts of minor proteins. The demonstration of this skeletal structure in "free" extrachromosomal nucleoli excludes the problem of contaminations by nonnucleolar material such as perinucleolar heterochromatin normally encountered in studies of nucleoli from somatic cells. It is suggested that this insoluble protein filament complex forms a skeleton specific to the nucleolus proper that is different from other extraction-resistant components of the nucleus such as matrix and lamina and is involved in the spatial organization of the nucleolar chromatin and its transcriptional products.
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PMID:A nucleolar skeleton of protein filaments demonstrated in amplified nucleoli of Xenopus laevis. 616 28

A unique DNA-binding protein was detected that inhibited DNA degradation induced by bleomycin and was decreased in sera of cancer patients. The protein from normal human serum was purified to homogeneity by ammonium sulfate precipitation and DEAE-cellulose and DNA-cellulose column chromatography. Two-dimensional isoelectric focusing gel electrophoresis revealed a single protein spot with a molecular weight of 64,000 and a pI at pH 5.9. The NH2 terminus was lysine, and the ratio of acidic to basic residues was 1.2. DNA binding was demonstrated by column chromatography, agarose gel electrophoresis, fluorescence quenching, and circular dichroism. The inhibitory activity was abolished by treatment with Pronase but not by RNase or DNase I. FeCl2 caused a partial loss of inhibitory activity. The inhibition of DNA degradation was more effective for breakage induced by bleomycin than neocarzinostatin, macromomycin, or DNase I. Evidence from DNA-binding studies suggests the inhibition is due to binding of the protein to sites on DNA preferred by bleomycin. Thus, the protein could be useful for studies on the mechanism of action of bleomycin and other antitumor agents, the cytotoxic effects of which are due primarily to damage of cellular DNA. The protein was decreased significantly in sera of cancer patients, and its potential use as a diagnostic tool for neoplasias is being investigated further.
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PMID:Inhibition of PM-2 DNA degradation by a human serum protein. 617 27

Morphologically intact nuclei have been prepared from embryos of Drosophila melanogaster by a simple and rapid procedure. These nuclei have been further treated with high concentrations of DNase I and RNase A followed by sequential extraction with 2% Triton X-100 and 1 M NaCl to produce a structurally and biochemically distinct preparation designated Drosophila subnuclear fraction I (DSNF-I). As seen by phase-contrast microscopy, DSNF-I is composed of material which closely resembles unfractionated nuclei; residual internal nuclear structures including nucleolar remnants are clearly visible. By transmission electron microscopy, nuclear lamina, pore complexes, and a nuclear matrix are similarly identified. Biochemically, DSNF-I is composed almost entirely of protein (greater than 93%). SDS PAGE analysis reveals several major polypeptides; species at 174,000, 74,000, and 42,000 predominate. A polypeptide coincident with the Coomassie Blue-stainable 174-kdalton band has been shown by a novel technique of lectin affinity labeling to be a glycoprotein; a glycoprotein of similar or identical molecular weight has been found to be a component of nuclear envelope fractions isolated from the livers of rats, guinea pigs, opossums, and chickens. Antisera against several of the polypeptides in DSNF-I have been obtained from rabbits, and all of them show only little or no cross-reactivity with Drosophila cytoplasmic fractions. Initial results of immunocytochemical studies, while failing to positively localize either the 174- or 16-kdalton polypeptides, demonstrate a nuclear localization of the 74-kdalton antigen in all of several interphase cell types obtained from both Drosophila embryos and third-instar larvae.
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PMID:Isolation and characterization of a proteinaceous subnuclear fraction composed of nuclear matrix, peripheral lamina, and nuclear pore complexes from embryos of Drosophila melanogaster. 617 1

Nuclear matrix was prepared by sequential treatment of oviduct nuclei with Triton X-100, DNase I, and 2 M NaCl. Published procedures were modified such that as many steps as possible were performed at -20 degrees C to minimize endogenous ribonuclease activity. Examination of electron micrographs confirmed the isolation of intact nuclear matrix structures. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the proteins in these structures showed an absence of histones and an enrichment of certain nonhistone proteins. RNA was isolated from the nuclear matrix preparations and subjected to denaturing gel electrophoresis. Gels were analyzed by ethidium bromide staining and by hybridization of Northern blots to cloned DNA probes for ovalbumin, ovomucoid, 5.8S ribosomal RNA, and U1 RNA. All of the precursors to ovalbumin and ovomucoid mRNAs (including various splicing intermediates) and all of the precursors to ribosomal RNA were associated exclusively with the nuclear matrix fraction. By contrast, mature ovalbumin and ovomucoid mRNAs were distributed between matrix and nonmatrix fractions. These observations were further supported by quantitative hybridization analysis of the RNA in nuclear and matrix fractions. It was found that less than 50% of the mature message of intact nuclei was recovered in the matrix, while most significantly, over 95% of the mRNA precursors remained associated with the matrix. Finally, mature ribosomal RNAs and virtually all of the small nuclear RNAs (including U1 RNA) were also distributed between matrix and nonmatrix fractions. Our results suggest that all precursor RNAs (be they precursors to mRNA or rRNA) are exclusively associated with the nuclear matrix and support the notion that the nuclear matrix may be the structural site for RNA processing within the nuclei of eucaryotic cells.
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PMID:Ribonucleic acid precursors are associated with the chick oviduct nuclear matrix. 618 7


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