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)

The presence of a nuclear DNA polymerase in mouse sperm from adult testes has been confirmed and the properties of this enzyme further investigated. This activity was shown to be greatly enhanced by treating the spermatozoa with methanol or ethanol before incubation in the reaction medium or by their addition in small amounts to this medium. It was protected against degradation by nuclear proteases by adding soybean trypsin inhibitor and was stimulated by ATP. It was found to be Mg2+ dependent (optimum concentration: 7.5 mM), DNA dependent, and all four deoxynucleoside triphosphates were needed for optimal reaction. The radioactive acid-precipitable product of polymerization was not eliminated by organic solvents, nor by pronase, ribonuclease or by nuclease S1; however, it was converted to a large extent to acid-soluble products by pancreatic deoxyribonuclease. Since it was only partially solubilized by Triton X-100, it therefore did not appear to be preferentially associated with the nuclear membranes. The activity recovered after incubation depended also on the pH (optimum at pH 8.3) and did not work well in a medium for DNA polymerase alpha. The temperature for maximum incorporation of nucleotides was found to be 32 degrees C and, under our conditions, the reaction was linear for 30 min. The DNA polymerase activity was inhibited by low and high concentrations of KCl. It was not lowered by N-ethylmaleimide or p-hydroxymercuribenzoate; urea slightly stimulated the reaction and this stimulation was reversed by subsequent treatment with N-ethylmaleimide. Actinomycin D (40 mug/ml), ethidium bromide (25--50 muM), netropsin (5--50 mug/ml), and spermidine (0.5--2.5 mM) lowered the polymerization of DNA precursors. The nuclear enzyme could shift from the endogenous template to activated exogenous calf thymus DNA, the resulting nuclear radioactivity being reduced. The endogenous DNP template ability was not increased by deoxyribonuclease activation according to the method of Aposhian and Kornberg (J. Biol. Chem. (1962) 237, 519--525) suggesting that the amount of DNA polymerase associated with chromatin was probably limiting the reaction. The DNA polymerase activity detected in mouse sperm nuclei has numerous properties of low molecular weight DNA polymerases (DNA polymerase beta) reported in several eukaryotic organisms.
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PMID:Further characterization of a DNA polymerase activity in mouse sperm nuclei. 1 3

The incorporation of [3H]AAadenosine into cold trichloroacetic acid (TCA) insoluble material by the mouse 1-cell embryo has been studied. Incorporation of label was high immediately after fertilization, then decreased over the next 7 h with the sharpest decline occurring 3-5 h after fertilization. A small maximum was observed at the time of pronuclear DNA synthesis. Actinomycin D at a concentration which inhibited the cleavage of 1-cell embryos by 50% had little effect on this incorporation, which in the period 1-6 h post-fertilization was shown by autoradiography to be confined to the ooplasm of the newly fertilized ovum. [3H]Adenosine and poly ([3H]A) were released from embryo RNA labelled 1-3 h after fertilization with [3H]adenosine by digestion with a mixture of ribonucleases A and T1. The poly ([3H]A) segments were hydrolysed by alkali to 3'-[3H]AMP and [3H]adenosine ([3H]AMP/[3H]adenosine = 5/1), and by snake venom phosphodiesterase to 5'-[3H]AMP but very little [3H]adenosine. These results suggest that adenylation of RNA occurs soon after fertilization, that this is a cytoplasmic event, and that most of the newly synthesized poly ([3H]A) segments are joined to pre-existing poly (A) tracts. The unusual polynucleotide, poly (ADP-ribose), identified by its resistance to alkali and the release of 2'-(5''-phosphoribosyl)-5'[3H]AMP on incubation with snake venom phosphodiesterase, was also found in the ribonuclease digest.
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PMID:Adenylation and ADP-ribosylation in the mouse 1-cell embryo. 44 65

Purification of feline calicivirus was achieved by cycles of differential centrifugation and two cycles of sucrose gradient centrifugation. Feline calicivirus grown in the presence of Actinomycin D and 3H-uridine-5, sediments in 15% to 45% sucrose gradients and forms a peak of radioactivity which corresponds with the peak of infectivity. Ribonucleic acid (RNA) extracted from the peak radioactive fractions taken from the sucrose gradient sedimented as a single peak ahead of the 28S peak of cellular RNA. It was sensitive to ribonuclease and was presumed to be single stranded feline calicivirus RNA with sedimentation of 32S-35S. A single peak of radioactivity at 35S was extracted from purified virus by heating at 60 degrees for two minutes in 1% sodium dodecyl sulphate (SDS), or by heating at 37 degrees for 5 minutes at 1% SDS. Virus extracted at 37 degrees for 10 minutes in 1% SDS showed also a small peak at 16S and by 15 minutes at 37 degrees only a broad peak at 16S occurred. All peaks were susceptible to ribonuclease. A component sedimenting at 18S which was resistent to degradation by ribonuclease under the conditions outlined by Baltimore (4) and presumed to be double-stranded RNA was present in kitten kidney cells infected with feline calicivirus.
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PMID:Feline calicivirus: purification of virus and extraction and characterisation of its ribonucleic acid. 97 39

Actinomycin D, at a concentration that inhibits cellular ribonucleic acid (RNA) synthesis, inhibited the production of foot-and-mouth disease virus-induced RNA polymerase in baby hamster kidney cells. Inhibition was proportional to exposure time and reached 85% when actinomycin D was added 90 min before infection. Polymerase production was inhibited to the same extent in growth and minimal media, and the kinetics of its appearance were slightly different than in untreated cells. Enzyme preparations from actinomycin-treated cells having one-third to one-tenth the activity of untreated samples gave products with RNA profiles similar to those of controls. The 37S viral peak, 20S ribonuclease-resistant peak, and 26 to 28S peaks were present in all cases. Actinomycin D did not consistently inhibit virus production in either medium. Insulin did not prevent the actinomycin induced inhibition of polymerase and virus production from occurring.
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PMID:Effect of actinomycin D on virus-induced ribonucleic acid polymerase formation in foot-and-mouth disease virus-infected baby hamster kidney cells. 431 46

Regulation of GH-releasing hormone receptor (GHRH-R) messenger RNA (mRNA) expression was studied, with the ribonuclease protection assay, in the fetal rat pituitary gland and in MtT-S clonal cells. GHRH-R mRNA was first detected on embryonic day (E)19 and increased rapidly thereafter, to reach a maximum at E21. Incubation of E17 or E18 pituitaries with 50 nM dexamethasone (DEX), a synthetic glucocorticoid, induced GHRH-R mRNA expression, suggesting that glucocorticoids play a pivotal role in the developmental expression of this mRNA. In E19 pituitaries, 24 h treatment with DEX increased GHRH-R mRNA by 60%, and GH mRNA by 76%, but did not affect pit-1 mRNA level, suggesting that the effect of DEX is specific for expressions of GH mRNA and GHRH-R mRNA. The accumulation of GHRH-R mRNA by DEX was time dependent, and it was slightly enhanced by the protein synthesis inhibitor, puromycin (100 microM). In MtT-S cells (a pituitary cell line established from an estrogen-induced tumor), DEX induced GHRH-R mRNA expression within 2 h in a dose-dependent manner. This induction was augmented by puromycin (100 microM) or cycloheximide (3.5 microM). However, the RNA synthesis inhibitor Actinomycin D (1 microM) completely inhibited GHRH-R mRNA accumulation in response to either DEX or DEX plus puromycin, suggesting that glucocorticoids induce GHRH-R mRNA mainly through stimulation of mRNA transcription. These results suggest: that GHRH-R mRNA accumulation in the fetal pituitary gland of rats normally occurs at E19, probably because of the direct action of glucocorticoids on the pituitary gland, to stimulate GHRH-R mRNA transcription; and that the expression of glucocorticoid receptors is an important event in GH cell development in rats. Accordingly, immunocytochemical results suggest an increase in glucocorticoid receptors in immature GH cells between E17 and E18. The present results also imply that MtT-S cells may be a good model in which to further study the molecular mechanisms of the regulation of GHRH-R gene expression.
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PMID:Regulation of growth hormone-releasing hormone receptor messenger ribonucleic acid expression by glucocorticoids in MtT-S cells and in the pituitary gland of fetal rats. 1034 67

Leptin is a 16-kDa hormone with an array of biologic actions. We, and others, have demonstrated that leptin is critical to the development of liver fibrogenesis both in vitro and in the lean littermates of ob/ob mice exposed to carbon tetrachloride (CCl(4)). Controversy exists as to whether leptin can act as a direct cytokine in the development of increased collagen expression, and whether ob/ob mice are resistant to potential injury from CCl(4). Here, we provide evidence that strongly suggests that leptin acts to increase nascent production of mRNA for the alpha2(I) collagen gene based upon ribonuclease protection analysis (RPA). Actinomycin D, but not cyclohexamide, or the pan-neutralizing antibody to transforming growth factor beta one (TGFbeta1), significantly diminished the effect of leptin on total alpha2(I) collagen mRNA levels. Further evidence that leptin acts directly on HSCs to alter gene expression in liver wounding is demonstrated by enhanced binding of phosphorylated signal transduction and activator of transcription factor 3 (pStat3) to a cis-inducible element (SIE) oligonucleotide by electrophoretic mobility shift assay (EMSA). This consensus sequence is responsible for production of a critical collagen transcription factor, AP-1. Finally, we have demonstrated from the ob/ob mouse model that these animals are at least as sensitive to CCl(4) as their respective lean animals as assessed by serum alanine aminotransferase (ALT) measurements. Taken together, the current data provide a continued framework that leptin is a profibrogenic cytokine and plays a key role in liver fibrosis.
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PMID:Leptin induces increased alpha2(I) collagen gene expression in cultured rat hepatic stellate cells. 1270 94

Major increases occurred in the capacity of damaged potato leaf and tuber tissues to hydrolyse ribonucleic acid whilst relatively minor increases were found in the activity of acid phosphomonoesterase and acid phosphodiesterase. Partial purification of homogenates by gel filtration on Sephadex G-100 revealed that much of the increased capacity to degrade ribonucleic acid following damage was due to increased ribonuclease activity. Although appreciable differences in the elution patterns of tuber homogenates subjected to gel filtration were observed before and after the breaking of dormancy the increased ribonuclease activity following damage was a constant feature. Actinomycin D had a relatively small effect on preventing these increases in phosphate-ester hydrolase activities whilst the effect of cycloheximide was very pronounced. Isopycnic equilibrium centrifugation experiments, using deuterium oxide as a density label, provided no evidence that the increased enzyme activity following damage was due to synthesis of new enzyme.
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PMID:Increase in ribonuclease activity following mechanical damage to leaf and tuber tissues of Solanum tuberosum L. 2448 75