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 cytoplasmic, microsomal bound RNA-dependent RNA polymerase has been purified 2500-fold from rabbit reticulocyte lysates. The synthesis of RNA with the purified enzyme is absolutely dependent on the addition of an RNA template. The best template is hemoglobin messenger RNA, while bacteriophage RNA and poly(A,G) are less active, and DNA is completely inactive as a template. With poly(A,G) as a template, only UTP and CTP are incorporated into polynucleotide chains, indicating that the RNA polymerase is an RNA replicase and not a terminal transferase. With messenger RNA as a template, all four ribonucleoside triphosphates are required for maximal activity. The RNA-dependent RNA polymerase reaction is extremely sensitive to low concentrations of heme, rifamycin AF/013, and ribonuclease and resistant to actinomycin D and DNase. The discovery of RNA-directed RNA synthesis in reticulocytes offers an additional site for control of gene expression in mammalian cells and provides a possible mechanism for amplification of the expression of specific genes.
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PMID:Reticulocyte RNA-dependent RNA polymerase. 451 33

The presence is reported of an RNA-instructed DNA polymerase in visna virus, the causative agent of a "slow" neurological disease in sheep. The product synthesized by the RNA-directed reaction has been shown to be a DNA heteropolymer by the following criteria: synthesis requires the presence of all four deoxyriboside triphosphates; the product is resistant to ribonuclease and alkali but is degraded by DNase; and the product has a density of 1.420 in Cs(2)SO(4) solution, characteristic of DNA.Visna virions, like those of the oncogenic RNA viruses, contain DNA polymerase activities that respond to a variety of double-stranded DNAs and to synthetic DNA.RNA hybrids.
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PMID:DNA polymerase activities in varions of visna virus, a causative agent of a "slow" neurological disease. 499 14

Insulin-like growth factor-II (IGF-II) is a secreted 67-amino acid peptide that functions principally as a prenatal growth regulator in mammals. To date, the mechanisms involved in the stimulation of IGF-II expression in the embryo and its attenuation after birth are unknown. Recent studies have shown that IGF-II mRNA and protein are induced during the terminal stages of muscle development in vitro, and that IGF-II may act as an autocrine differentiation agent for skeletal myoblasts. We now have investigated the regulation of IGF-II gene expression in muscle cells. Steady state levels of IGF-II mRNA increased by more than 30-fold during terminal differentiation of the C2 mouse myoblast cell line. Transcription run-on experiments using isolated muscle cell nuclei and direct analysis of nuclear RNA each demonstrated a greater than 10-fold rise in nascent IGF-II mRNA during cellular differentiation, and ribonuclease protection experiments showed that more than 95% of IGF-II mRNAs initiated in noncoding exon 3, implying that transcriptional activation occurs principally through promoter 3, the most 3' of the three mouse IGF-II gene promoters. Analysis of chromatin structure around the IGF-II gene in C2 cells revealed four major and four minor DNase-I-hypersensitive sites, but did not provide insight into the mechanisms of gene activation, since all sites were present in proliferating and differentiating cells. Gene transfer experiments showed that promoter 3 was at least 50-fold more active than promoter 1 or 2 in C2 cells, but the functional assessment of nearly 26 kilobases of additional DNA within the IGF-II locus by an "enhancer trap" approach did not delineate any chromosomal regions capable of mediating differentiation-specific gene activation. Our results demonstrate that muscle cells encode mechanisms for activating IGF-II gene transcription and suggest that these cells may be excellent models for identifying the developmentally regulated factors that control IGF-II gene expression.
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PMID:Transcriptional activation of the insulin-like growth factor-II gene during myoblast differentiation. 846 41

In this report, we describe the molecular cloning and characterization of DLAD, a novel mammalian deoxy-ribonuclease homologous to DNase II. The full length cDNA for mouse DLAD has been cloned by polymerase chain reaction. The cDNA contains a 1065 bp open reading frame (ORF) encoding a 354 amino acid protein with a calculated molecular mass of 40 767. The predicted protein for DLAD shares 34.4% identity with DNase II. DLAD is also homologous to three predicted proteins, C07B5.5, F09G8.2 and K04H4.6, from the nematode Caenorhabditis elegans. Furthermore, the third ORF of the fowlpox virus genome is found to encode a DLAD homologue showing 37. 1% identity at the amino acid level. Northern blot analysis reveals that expression of the DLAD mRNA is highly restricted to the liver. DLAD mainly exists as a cytoplasmic protein with divalent cation-independent endonuclease activity and cleaves DNA to produce 3'-phosphoryl/5'-hydroxyl ends. It is active under a wide range of pH with maximum activity at pH 5.2. Among known DNase inhibitors tested, aurintricarboxylic acid and Zn(2+)are found to be effective inhibitors of the DLAD activity.
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PMID:DLAD, a novel mammalian divalent cation-independent endonuclease with homology to DNase II. 1049 74

High-carbohydrate feeding and triiodothyronine (T3) increase the abundance of acetyl-CoA carboxylase-alpha (ACC alpha) mRNA in avian hepatocytes, whereas starvation, glucagon, and medium-chain fatty acids decrease the abundance of ACC alpha mRNA. These changes in ACC alpha mRNA levels are mediated by alterations in the rate of transcription of the ACC alpha gene. In liver, ACC alpha transcription is initiated from two promoters, promoter 1 and promoter 2, resulting in transcripts that contain heterogeneity in their 5'-untranslated regions. Here, we investigated the role of promoter 1 and promoter 2 in mediating nutrient- and hormone-induced changes in ACC alpha mRNA abundance by measuring the level of transcripts expressed from promoter 1 and promoter 2 using a ribonuclease protection assay. The results indicated that both promoter 1 and promoter 2 were regulated by starvation/refeeding in livers of intact chicks and by T3, glucagon, and medium-chain fatty acids in chick embryo hepatocyte cultures and that alterations in the activity of promoter 2 accounted for a greater proportion of the changes in total ACC alpha mRNA abundance caused by nutrient and hormone treatment. Five DNase-hypersensitive sites were also identified between -500 and +1 bp relative to the transcription start site of promoter 2 in livers of intact chicks and in chick embryo hepatocyte cultures. In transient transfection analyses, this region of DNase hypersensitivity conferred regulation of transcription by T3, glucagon, and medium-chain fatty acids in chick embryo hepatocytes. Data from this study demonstrate that diet-induced changes in the activities of promoter 1 and promoter 2 in livers of intact chicks are mimicked in chick embryo hepatocyte cultures by manipulating the concentrations of T3, glucagon and medium-chain fatty acids in the culture medium and that cis-acting sequences mediating the effects of nutrients and hormones on promoter 2 activity are located immediately upstream of the transcription start site of this promoter.
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PMID:Thyroid hormone, glucagon, and medium-chain fatty acids regulate transcription initiated from promoter 1 and promoter 2 of the acetyl-CoA carboxylase-alpha gene in chick embryo hepatocytes. 1111 20

Basal, "insulin-independent" glucose uptake into skeletal muscle is provided by glucose transporters positioned at the plasma membrane. The relative amount of the three glucose transporters expressed in muscle has not been previously quantified. Using a combination of qualitative and quantitative ribonuclease protection assay (RPA) methods, we found in normal human muscle that GLUT1, GLUT3, and GLUT4 mRNA were expressed at 90 +/- 10, 46 +/- 4, and 156 +/- 12 copies/ng RNA, respectively. Muscle was fractionated by DNase digestion and differential sedimentation into membrane fractions enriched in plasma membranes (PM) or low-density microsomes (LDM). GLUT1 and GLUT4 proteins were distributed 57% to 67% in LDM, whereas GLUT3 protein was at least 88% in the PM-enriched fractions. These data suggest that basal glucose uptake into resting human muscle could be provided in part by each of these three isoforms.
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PMID:Comparison of GLUT1, GLUT3, and GLUT4 mRNA and the subcellular distribution of their proteins in normal human muscle. 1114 24

Nucleic acids in young leaves of Swiss chard have been studied by light and electron microscope techniques. Leaf DNA has also been characterized by density gradient centrifugation and shown to contain a minor band of higher guanine plus cytosine (GC) content, presumably attributable to chloroplasts. The chloroplasts were faintly stained by the Feulgen reaction; radioautography demonstrated the incorporation of tritiated thymidine in the cytoplasm and in some nuclei. The Feulgen stainability and most of the radioactivity were removable with DNase. Under the electron microscope, both mitochondria and chloroplasts were found to contain filamentous and particulate components within the matrix areas. The morphology of the filamentous component was dependent on the fixation, being partially clumped after OSO(4) or formalin, but finely filamentous after Kellenberger fixation. The filaments were stainable with uranyl acetate, and were extractable with DNase following formalin fixation under conditions in which nuclear DNA was also extracted. The particulate component, after formalin fixation and uranyl staining, was prominent in chloroplasts from young leaves, but was only sparsely distributed in mitochondria. The stainability was removed with ribonuclease. We have concluded that chloroplasts and mitochondria of Swiss chard possess a filamentous component that contains DNA, probably responsible for both cytoplasmic thymidine incorporation and the minor band in CsCl centrifugation. A particulate ribosome-like component that contains RNA is also present.
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PMID:NUCLEIC ACIDS OF CHLOROPLASTS AND MITOCHONDRIA IN SWISS CHARD. 1428 84

The profile of major ribonuclease (RNase) activities of Arabidopsis thaliana has been identified and characterized using a substrate-based gel assay. Following sodium dodecyl sulfatepolyacrylamide gel electrophoresis, as many as 16 RNases, varying in size from 9 to 41 kilodaltons can be detected. Most of the RNase activities exhibit a pH optimum of about 6.5; however, the activity of a 22.6-kilodalton RNase is greatly enhanced at low pH. A number of the RNases in the 30- to 41-kilodalton range are sensitive to ethylenediaminetetraacetic acid, and their activities are enhanced by the presence of a low concentration of zinc during renaturation. At least one RNase appears to comigrate with a major DNase activity. The differential accumulation of several RNases in stems versus leaves indicates that some RNases are controlled in an organ-specific manner in A. thaliana.
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PMID:Identification and Properties of the Major Ribonucleases of Arabidopsis thaliana. 1666 75

Although the human mitochondrial genome has been investigated for several decades, the proteins responsible for its replication and expression, especially nucleolytic enzymes, are poorly described. Here, we characterized a novel putative PD-(D/E)XK nuclease encoded by the human C20orf72 gene named Ddk1 for its predicted catalytic residues. We show that Ddk1 is a mitochondrially localized metal-dependent DNase lacking detectable ribonuclease activity. Ddk1 degrades DNA mainly in a 3'-5' direction with a strong preference for single-stranded DNA. Interestingly, Ddk1 requires free ends for its activity and does not degrade circular substrates. In addition, when a chimeric RNA-DNA substrate is provided, Ddk1 can slide over the RNA fragment and digest DNA endonucleolytically. Although the levels of the mitochondrial DNA are unchanged on RNAi-mediated depletion of Ddk1, the mitochondrial single-stranded DNA molecule (7S DNA) accumulates. On the other hand, overexperssion of Ddk1 decreases the levels of 7S DNA, suggesting an important role of the protein in 7S DNA regulation. We propose a structural model of Ddk1 and discuss its similarity to other PD-(D/E)XK superfamily members.
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PMID:Identification of a novel human mitochondrial endo-/exonuclease Ddk1/c20orf72 necessary for maintenance of proper 7S DNA levels. 2335 26

S-type pyocins are bacteriocins produced by Pseudomonas aeruginosa isolates to antagonize or kill other strains of the same species. They have a modular organization comprising a receptor-binding domain recognizing a surface constituent of the target bacterium, a domain for translocation through the periplasm, and a killing or toxic domain with DNase, tRNase, or pore-forming activity. Pyocins S2, S3, S4, and S5 recognize TonB-dependent ferri-siderophore receptors in the outer membrane. We here describe a new nuclease bacteriocin, pyocin S6, encoded in the genome of a P. aeruginosa cystic fibrosis (CF) clinical isolate, CF_PA39. Similarly to pyocins S1 and S2, the S6 toxin-immunity gene tandem was recruited to the genomic region encoding exotoxin A. The pyocin S6 receptor-binding and translocation domains are identical to those of pyocin S1, whereas the killing domain is similar to the 16S ribonuclease domain of Escherichia coli colicin E3. The cytotoxic activity was abolished in pyocin S6 forms with a mutation in the colicin E3-equivalent catalytic motif. The CF_PA39 S6 immunity gene displays a higher expression level than the gene encoding the killing protein, the latter being only detected when bacteria are grown under iron-limiting conditions. In the S1-pyocinogenic strain P. aeruginosa ATCC 25324 and pyocin S2 producer P. aeruginosa PAO1, a remnant of the pyocin S6 killing domain and an intact S6-type immunity gene are located downstream of their respective pyocin operons. Strain PAO1 is insensitive for pyocin S6, and its S6-type immunity gene provides protection against pyocin S6 activity. Purified pyocin S6 inhibits one-fifth of 110 P. aeruginosa CF clinical isolates tested, showing clearer inhibition zones when the target cells are grown under iron limitation. In this panel, about half of the CF clinical isolates were found to host the S6 genes. The pyocin S6 locus is also present in the genome of some non-CF clinical isolates.
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PMID:Identification and functional analysis of a bacteriocin, pyocin S6, with ribonuclease activity from a Pseudomonas aeruginosa cystic fibrosis clinical isolate. 2686 Apr 27


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