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

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Query: EC:3.1.26.9 (ribonuclease)
6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A ribonuclease was isolated and completely purified from sporulating cells of Bacillus subtilis. This RNase has a M.W. of about 150,000 daltons. It hydrolyzes single stranded RNA and single stranded synthetic polynucleotides yielding nucleoside 5'-monophosphates. The enzyme is an exonuclease which degrades polynucleotides from the 3'-end in the direction of the 5'-terminal. The RNase activity is strikingly inhibited by cGMP and to a lesser extent by cAMP. This inhibition (Ki = 0.1 mM) is of a non competitive nature. It appeared that in addition to the inhibition site, the enzyme contains a high affinity binding site for the two cyclic mononucleotides (K (cAMP) = 8.3 x 10-8; K (cGMP) = 2.5 x 10-7). The RNase activity is also strongly inhibited by spermidine. This inhibition appeared to be due to the polyamine binding with the RNA, thus lowering the affinity of the substrate for the active site of the enzyme. This RNase may play a role in vivo in selective degradation of newly synthesized mRNA during sporulation.
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PMID:Isolation and properties of a cyclic guanosine-monophosphate sensitive intracellular ribonuclease from Bacillus subtilis. 18 87

Theophyllin, an inhibitor of cAMP-degrading phosphodiesterase, stimulates melanin biosynthesis in cultures of RPMI 3460 hamster melanoma cells. Although theophylline does produce an initial transient elevation of intracellular cAMP levels, long-term treatment with theophylline produces a significant decrease in cAMP content. There is an inhibition of the theophylline stimulation by dibutyryl-cAMP; this is apparently caused by interference of dibutyryl-cAMP with the uptake and incorporation of theophylline, as shown by experiments with 3H-theophylline. An alternative theory is that theophylline, being a methylxanthine compound, is metabolized by the cell and possibly causes melanotic stimulation by becoming incorporated into cellular nucleic acids or by altering the normal nucleic acid metabolism. The following observations are consistent with this theory: (u) 3H-theophylline was incorporated into both trichloroacetic acid (TCA)-soluble and TCA-insoluble cell fractions; most of the insoluble label became soluble after digestion with ribonuclease and deoxyribonuclease. (2) These nuclease digests of the 3H-theophylline-labeled TCA-insoluble cell fractions contained 3H-labeled material that chromatographed differently from normal nucleotides on ion exchange thin layer sheets. (3) The acid-soluble pool of 3H label disappeared rapidly while both the insoluble label and the induction of melanogenesis remained stable for 50 hr after the removal of exogenous 3H-theophylline.
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PMID:Theophylline incorporation into the nucleic acids of theophylline-stimulated melanoma cells. 21 85

Cyclic AMP-dependent protein kinases from several mammalian sources inhibit Na+-dependent alpha-aminoisobutyric acid transport by membrane vesicles isolated from 3T3 cells. Evidence is provided that phosphorylation of membrane proteins by the enzyme is responsible for the inhibition. Lysis of the vesicles, or a reduction in the intravesicular volume is not the cause of reduced transport. The cyclic AMP-dependent protein kinase and its catalytic subunit phosphorylate a number of membrane proteins. Most of these proteins are phosphorylated, but to a lesser extent in the absence of protein kinase or cyclic AMP. The phosphorylated proteins remain associated with the membranes during hypotonic lysis treatments, which would be expected to release intravesicular contents and loosely associated membrane proteins. 32P-labeled bands detected on sodium dodecyl sulfate polyacrylamide gels after phosphorylation of membranes by the catalytic subunit of the cyclic AMP-dependent kinase are eliminated by treatment with either pronase or 1 N NaOH, but not by ribonuclease nor by phospholipase C. The stability of the incorporated radioactivity to hot acid and hydroxylamine relative to hot base suggests that most of the 32P from [gamma-32P]ATP is incorporated into protein phosphomonoester linkages.
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PMID:Inhibition of alpha-aminoisobutyric acid transport in membrane vesicles from mouse fibroblasts after phosphorylation by cyclic AMP-dependent protein kinase. 22 60

Rat ventricular cardiac muscle has previously been shown to contain exceptionally high levels of preproenkephalin mRNA (ppEnk mRNA). We have recently determined that the level of ppEnk mRNA is developmentally and hormonally regulated in rat ventricular cardiac muscle tissue and in cultured myocytes (J. P. Springhorn and W. C. Claycomb. Biochem. J. 258: 73-77, 1989). We demonstrate in the current study that heart ppEnk mRNA is structurally identical at the 5' end to brain ppEnk mRNA using a ribonuclease protection assay and that heart ppEnk mRNA can be translated in vitro using a rabbit reticulocyte lysate system. In vitro synthesized preproenkephalin peptides were immunoprecipitated with a polyclonal antibody directed to the carboxy-terminal seven amino acids of preproenkephalin. We have also established by radioimmunoassay that enkephalin-containing peptides are secreted from cultured neonatal and adult rat ventricular cardiac muscle cells. This secretion is linear with respect to time and can be stimulated by phorbol 12-myristate 13-acetate (PMA) and adenosine 3',5'-cyclic monophosphate (cAMP). It was determined by column chromatography that cAMP induced neonatal rat ventricular cardiac muscle cells to secrete Met5-enkephalin-Arg6-Phe7, whereas PMA plus 3-isobutyl-1-methylxanthine induced adult rat ventricular cardiac muscle cells to secrete Met5-enkephalin. These studies establish that ventricular heart muscle ppEnk mRNA can be translated and that enkephalin peptides are secreted from ventricular cardiac muscle cells.
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PMID:Translation of heart preproenkephalin mRNA and secretion of enkephalin peptides from cultured cardiac myocytes. 127 91

The effects of hCG, 8-bromo-cAMP, 4 beta-phorbol 12 beta-myristate 13 alpha-acetate, and forskolin on insulin-like growth factor-I (IGF-I) receptor gene expression of Leydig cells were studied. The treatment of purified Leydig cells with hCG caused a dose-dependent increase in [125I]IGF-I binding to Leydig cells without changes in binding affinity, indicating that the increased binding was due to increased receptor numbers and not to increased affinity. The minimal time required for hCG to induce IGF-I binding was 6 h, and it had reached a plateau at 16 h. 8-Bromo-cAMP (1 mM) increased IGF-I binding about 2-fold, and forskolin (10 microM) increased binding about 51%. Using the ribonuclease protection assay, we found that hCG and 8-bromo-cAMP could increase IGF-I receptor mRNA expression as early as 2 h before the increase in IGF-I binding. The induction by hCG was over 3.5-fold at 4 h and decreased to about 2-fold at 6 h. 4 beta-Phorbol 12 beta-myristate 13 alpha-acetate had a very small effect on IGF-I receptor mRNA levels (1.5-fold increase at 2 h and no changes at 4 and 6 h). In conclusion, IGF-I receptors can be up-regulated by hCG, 8-bromo-cAMP, and forskolin. The up-regulation of IGF-I receptor number is associated with transient increases in IGF-I receptor mRNA levels. This could be a mechanism by which hCG and IGF-I interact to enhance Leydig cell steroidogenesis.
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PMID:Human chorionic gonadotropin up-regulates insulin-like growth factor-I receptor gene expression of Leydig cells. 165 15

We studied the 5' untranslated regions (UTRs) of the mouse lymphocyte pore-forming protein (PFP, perforin, and cytolysin). 5' UTRs were determined by primer extension analysis, sequencing PFP cDNA clone PFP-7, ribonuclease protection assays, and amplification of poly(A)+ RNA of cytolytic T lymphocyte using polymerase chain reaction (PCR). Two alternatively spliced 5' UTRs, designated type I and type II, of 222 and 115 bp, respectively, were found associated with PFP. Type II is identical to type I, except for being 107 bp shorter in the second exon. This deletion was generated by the use of alternative acceptor splice sites. The mouse PFP gene (Pfp) encodes three exons, is separated by two small introns, and spans a chromosomal region of approximately 7 kb. The first exon contains 79 bp of 5' UTR, the second exon contains 143 or 36 bp of 5' UTR (type I or type II UTR, respectively) plus the NH2-terminal region of the mouse PFP, and the third exon contains the rest of the COOH-terminal mouse PFP. The organization of the mouse Pfp is similar to that of the human gene. Moreover, the 5' flanking sequence of the mouse Pfp is highly homologous to that of the human Pfp. In contrast to the human sequence, the more immediate 5' flanking sequence of mouse Pfp contains two tandem "TATA" box-related elements and a GC box, but lacks a typical CAAT box-related sequence. Several other enhancer elements were found further upstream, including cAMP-, phorbol ester-, interferon-gamma-, and UV-responsive elements, and PU box-like and NFkB binding site-like elements. In addition, we found a nuclear inhibitory protein-like element, a transcriptional silencer, and a pair of purine-rich sequence motifs that were found in other T cell-specific genes, and three repeats of GGCCTG that may be a variation of a highly repetitious GCCCTG consensus sequence found in human Pfp.
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PMID:Structure of the mouse pore-forming protein (perforin) gene: analysis of transcription initiation site, 5' flanking sequence, and alternative splicing of 5' untranslated regions. 184 Jun 7

Brief exposure of Chinese hamster ovary cell monolayers prelabeled with [(32)P]phosphate and [(3)H]leucine to 1 mug/ml of trypsin under conditions in which cells remain fully viable causes the release of macromolecular (32)P and (3)H. Whereas ribonuclease treatment was found to affect markedly both the (32)P and (3)H radioactivity, Pronase treatment had little effect on the macromolecular (32)P. Treatment of cells prelabeled with [(3)H]glucosamine and [(32)P]phosphate with insolubilized papain also revealed a parallel release of macromolecular glucosamine together with ribonuclease-susceptible macromolecular phosphate. Lactoperoxidase-mediated radioiodination of surface components in cells prelabeled with [(32)P]phosphate revealed electrophoretic comigration between the (125)I and the (32)P that are removed from the cells by mild proteolysis. Growth of the cells in Bt(2)cAMP-testosterone altered the kinetics of release and nature of the macromolecular (32)P liberated by proteolysis.
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PMID:An "external" RNA removable from mammalian cells by mild proteolysis. 453 Oct 29

Evidence is presented that isoproterenol treatment of rat C6 glioma cells, under conditions that increase glioma cell cAMP levels, causes the phosphorylative modification of several RNA polymerase II subunits. RNA polymerase II in control and isoproterenol-stimulated 32Pi-labeled confluent glioma cells was immunoprecipitated from ribonuclease-treated nuclear extracts with hen anti-calf RNA polymerase II antiserum conjugated to Sepharose. The immunoprecipitated RNA polymerase II was analyzed for 32P-labeled subunits by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels. Using this technique, we have shown that isoproterenol causes a time-dependent increase of phosphate incorporation into RNA polymerase II subunits of 214,000, 180,000, 140,000, 35,000, 28,000, and 16,500 daltons. Phosphate incorporation occurred exclusively on serine in all of the six subunits. About 0.5-2 mol of phosphate/mol of RNA polymerase II subunit were incorporated. Dibutyryl cAMP (10(-3)M) mimics the stimulatory action of isoproterenol and mediates increased phosphate incorporation into the six subunits. (RS)-propranolol (10(-4)M) prevents the isoproterenol-mediated phosphorylative changes. These data indicate that isoproterenol, via cAMP, mediates a transient structural modification of RNA polymerase II subunits in rat C6 glioma cells which may possibly lead to a modulation of RNA polymerase II function(s).
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PMID:Phosphorylation of rat C6 glioma cell DNA-dependent RNA polymerase II in vivo. Identification of phosphorylated subunits and modulation of phosphorylation by isoproterenol and N6,O2'-dibutyryl cyclic AMP. 609 70

The effect of thyrotropin (TSH) on the ADP-ribosylation of endogenous thyroid cell acceptor proteins was examined. Cells were "permeabilized" at 4 degrees C in hypotonic medium and then exposed to [(32)P]- or [(3)H-adenine]NAD(+). The net incorporation of labeled ADP-ribose was measured by trichloroacetic acid precipitation. TSH (100 mU/ml) enhanced ADP-ribosylation with a maximum effect after 30-60 min in the majority of experiments. TSH stimulation was observed even when the incubation contained 1,000-fold more exogenous NAD(+) than the amount of NAD(+) contributed by the permeabilized cells, indicating an effect on enzymatic activity rather than an alteration in NAD(+) pool size or specific activity. No incorporation of radioactivity from labeled NAD(+) was observed in cells not rendered permeable to NAD(+) by hypotonic shock. TSH did not increase the rate of disappearance of trichloroacetic-precipitable radioactivity and did not contain intrinsic NAD(+) glycohydrolase activity. Alkali and snake venom phosphodiesterase, but not ribonuclease or deoxyribonuclease digestion of trichloroacetic acid precipitable thyroid cell radioactivity, revealed primarily 5'-AMP, consistent with an effect of TSH on mono-ADP ribosylation. Nicotinamide and thymidine (50 mM) inhibited both basal and TSH-stimulated ADP-ribosylation of thyroid cell protein. Dibutyryl cyclic (c)AMP (0.1 mM) inhibited endogenous ADP-ribosylation by approximately 35% but had no effect at lower concentrations. 0.5 mM isobutylmethylxanthine inhibited this reaction by approximately 60%. We suggest that TSH enhances thyroid cell ADP-ribosylation by a mechanism independent of cAMP as a second messenger, and that ADP-ribosylation plays a role in the expression of TSH.
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PMID:Hormonal stimulation of eucaryotic cell ADP-ribosylation. 626 5

A nuclear p53/55 protein kinase has been isolated from nuclear ribonucleoprotein particles from human tumor cells. The enzyme was purified approximately 2200-fold cell nuclei by sequential ribonuclease digestion of the RNP particles, DEAE cellulose and phosphocellulose chromatography. The kinase which was cAMP independent, catalyzed the phosphorylation of rabbit muscle glycogen synthase in the amino terminal domain, and conversion of the I to D form. The D synthase had a phosphorylation stoichiometry of 8 moles 32P per mole of synthase subunit with maximal specificity for ATP as phosphate donor; its Km was 30 microM. An antinucleolar antibody inhibited enzyme activity by 80%. Substrates for most other kinases were inactive. The kinase was essentially unaffected by the Walsh inhibitor, EGTA, regulatory subunits of protein kinase, calmodulin, trifluoperazine or heparin. Its activity was lost at 1 mM polyamine, but was enhanced 3-fold by MnCl2 and 4- to 9-fold by deoxymononucleotides. The nuclei of HeLa cells contained 64% of the total kinase of which 64% of the total kinase of which 11% were in nucleoli; the specific activity of the nucleolar kinase was twice that of the nuclear supernatant and four times that of the cytoplasmic kinase. These results indicate that nucleolar ribonucleoprotein particles of human tumor cells contain a cAMP-independent protein kinase which is similar to glycogen synthase kinase.
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PMID:Purification of p53/55 kinase from nuclear ribonucleoproteins of Namalwa cells. 643 81


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