Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.13.1 (exoribonuclease)
 732 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The specific activity of alkaline RNase II was l00 to 1800 times higher in mouse pancreas than in mouse liver, serum, ascites fluid, and Ehrlich ascites cell grown intraperitoneally. Ehrlich ascites cells grown in cell culture medium had a much lower alkaline RNase II activity than cells grown intraperitoneally. Chromatography on CM-52 cellulose of acid- and heat-treated preparations showned a considerable heterogeneity of the mouse enzymes. Depending on the source of the extract, two to six forms fo alkaline RNase were eluted. Pancreatic extract contained two RNase forms. These also seemed to be present as minor components in preparations from other sources except Ehrlich ascites cells grown in vitro. Ehrlich ascites cells grown in vivo contained forms of the RNase which were not present in other extracts. Possible reasons for this heterogeneity were investigated. In addition to their stability to acid and heat the different RNase forms were similar in that they were much more active at alkaline pH than at acidic pH, they did not require divalent metal ions for activity, and they degraded RNA 'endonucleolytically.' Also, native DNA, denatured DNA, and poly A were poor substrates compared with RNA. Some differences seemed to exist, however, with respect to their abilities to degrade poly U and poly C and their sensitivities to the endogenous RNase inhibitor.
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PMID:Heterogeneity of alkaline ribonuclease in the mouse and Ehrlich ascites cells. 2 28

We have investigated three aspects of RNA turmor virus replication and cell transformation: (1) the properties of the purified avian and mammalian viral RNA-directed DNA polumerase, (2) some characteristics of the viral 60-70S RNA genome, 30-40S RNA subunits and intracellular viral RNA species, and (3) the interaction of the viral DNA polymerase with its RNA template early during infection and cell transformation by the murine sarcoma-leukemia virus (MSV[MLV]). Avian myeloblastosis virus (AMV) contains two forms of RNA-directed DNA polymerase, alpha, consisting of a single polypeptide of molecular weight 65,000, and alphabeta, consisting of two polypeptides of molecular weights 65,000 and 105,000. The alpha and alphabeta forms of AMV DNA polymerase both possess RNase H activity that requires free end termini on the ribopolymer and can degrade the RNA of the RNA-DNA hybrid in the 3' to 5' and 5' to 3' directions. But, alpha and alphabeta possess a different mode of exoribonuclease activity. While alphabeta RNase H is a processive exoribonuclease that degrades the polynucleotide chain to a core residue before attacking a second chain, alpha RNase H is a random exoribonuclease that releases the polynucleotide after each scission. Highly purified Moloney-MSV(MLV) DNA polymerase has both RNase H activity and the ability to read viral 60-70S RNA. These activities comigrate through five different steps of purification and are present at levels comparable to those found in purified AMV DNA polymerase. The MSV(MLV) 60-70S RNA genome and 35S RNA subunits were shown by periodate oxidationtritiated borohydride reduction to contain adenosine as the major 3'-terminal nucleoside. Poly (A) segments were isolated from viral 60-70S and 35S RNA by treatment with RNase A or RNase T1 and purified by afinity chromatography and gel electrophoresis. Viral poly(A) was shown to be present at the 3' terminus as -G(C,U)A190AOH. The similar sequence reported for poly(A) present in mammalian mRNA suggests that similar mechanisma are involved in the transcription and processing of both cellular and viral DNA sequences. Within transformed cells replicating MSV(MLV), viral 35S and 20S RNA were found in membrane-bound polyribosomes, whereas only 35S RNA was detected in free polyribosomes. The origin and function of 20S RNA is unknown. The early events during rapid infection and cell transformation of mouse 3T6 cells by the Harvey strain of MSV(MLV) were studied. By both autoradiographic analysis and molecular hybridization, viral DNA synthesis was detected in the cytoplasm by 1 hour after infection, reached a maximum at 2 hours, and subsequently decreased. Cytological chase experiments produced evidence that cytoplasmic viral DNA was transported to the nucleus. In situ hybridization experiments using radioactive viral DNA product as a probe demonstrated the rapid association of viral DNA sequences with the chromocenters of interphase nuclei and with the centromeric heterochromatin regions of some chromosomes.
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PMID:Properties of oncornavirus RNA-directed DNA polymerase, the RNA template, and the intracellular products formed early during infection and cell transformation. 5 Sep 2

The infectivity of replicative form RNA (RF-RNA) isolated from poliovirus-infected HeLa cells is completely resistant to the action of T-1 RNase but decreases after exposure to RNase A in the presence of 0.3 M NaCl. Under these conditions neither enzyme produces single-stranded nicks in RF-RNA. Three endonuclease-free exonuleases (RNase II, polynucleotide phosphorylase and spleen phosphodiesterase) rapidly destroy the infectivity of single-stranded RNA, but do not alter the infectivity of RF-RNA. It is concluded that RF-RNA does not contain single-stranded ends essential for infectivity. Indirect evidence suggests that all or most of the poly A region at the 3' end of the plus strand of infectious RF-RNA is base-paired to a poly U region at the 5 end of the minus strand.
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PMID:Poliovirus-induced infectious double-stranded RNA: Effect of RNA-degrading enzymes. 16 28

The synthesis of N3-[3-L-(5-azido-2-nitrobenzamido)-3-carboxypropyl]uridine (4b) and N3-[3-carboxy-3-L-(2,2,5,5-tetramethyl-3-pyrroline-3-carbonylamino)propyl]uridine Npyr-oxyl (4c) starting from the nucleoside X (4a) and the appropriate N-hydroxysuccinimide ester 1 or 2 is described. After acylation of tRNAPhe from E. coli (5a) with 1 or 2, the photolabile tRNAPhe derivative 5b and the paramagnetic tRNAPhe derivative 5c could be isolated. The position of modification in the polynucleotide chain was elucidated by comparison of the ribonuclease II/alkaline phosphatase digestion products of the substituted and unsubstituted tRNAPhe samples, and was identified as being exclusively the amino group of the nucleoside X in position 47 of E. coli tRNAPhe.
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PMID:Photolabile and paramagnetic derivatives of the nucleoside X and of Escherichia coli tRNAPhe. 21 14

Further studies were made on the reassembly of 50S ribosomal subunits from proteins and RNAs of E. coli. The reassembled particles had high activity in poly U-directed polyphenylalanine synthesis and their sucrose sedimentation properties were similar to those of the original intact particles. Several factors affecting the reassembly were examined. The optimal pH for solubilization of ribosomal proteins was pH 9.5, and the optimal Tris concentration was 0.75 to 1.00 M. In the reassembly mixture the pH was adjusted to 8.2 A sharp optimum magnesium ion concentration of 6 to 10 mM was observed. The reassembly required 0.2 to 0.5 M KCl, the optimum concentration being 0.40 M. On incubation for 20 min a temperature of 34 and 40 degrees was necessary, 37 degrees being best. Oligonucleotides, which we previously added to the reassembly mixture were found not to be necessary for inhibition of RNase II [EC 3.1.4.20] activity remaining in the reaction was found necessary to dialyze the reassembly mixture against a buffer containing 10 mM magnesium ion after the incubation. Simultaneous reassembly of 30 and 50S subunits with time was observed, showing that 70S ribosomes were formed first and that they then dissociated into subunits. Reassembly of 50S subunits from their component proteins and RNAs was completely dependent on either 30S particles or the simultaneous reassembly of 30S subunits. Other critical factors affecting the reassembly of 50S subunits must be examined, since the reproducibility of this reassembly is only about 60%, even under the above controlled conditions.
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PMID:Reassembly of functionally active 50S ribosomal particles from proteins and RNAs of Escherichia coli. Dependency of 50S ribosomal reassembly on 30S subunits. 23 3

Exoribonuclease from rat liver cell nuclei was isolated and purified using selective extraction at pH 8.0, salting out with ammonium sulfate (30-50% saturation) and chromatography on DEAE-Sephadex A-50. The enzyme has the pH optimum 7.4-7.6, it requires Mg-2+. It catalyses the gradual removal of ribonucleoside-5'-monophosphates from synthetic polynucleotides and RNA; it preferably attacks single-stranded polynucleotides and is less efficient when hydrolysing poly-stranded helical polymers. It is supposed that exoribonuclease can participate in the destruction of non-informative regions in new-formed hyper-molecular RNA of cell nuclei.
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PMID:[Isolation and some properties of exoribonuclease from the cell nuclei of the rat liver]. 23 81

A new ribonuclease has been isolated from Escherichia coli. The enzyme is present in the 100,000 times g supernatant fraction and has been purified over 200-fold. Studies of the enzyme reveal that: 1. The enzyme shows a marked preference for oligoribonucleotides; indeed, the reaction rate is inversely proportional to the chain length of the substrate. The enzyme does not attack polynucleotides even at high concentrations of enzyme and has no detectable DNase activity. 2. The enzyme is stimulated strongly by Mn2+, less strongly by Mg2+, and not at all by Ca2+ and monovalent cations. 3. The enzyme is purified free of RNase I, RNase II, RNase III, polynucleotide phosphorylase, and other known ribonucleases of E. coli. The enzyme displays identical properties when isolated from mutants of E. coli that are deficient in the above ribonucleases. 4. The enzyme has a marked thermostability, a point of further distinction from RNase II.
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PMID:A novel oligoribonuclease of Escherichia coli. I. Isolation and properties. 24 Aug 24

The acid-soluble ribonucleic acid degradation products formed by Escherichia coli cells starved for a carbon source have been identified. They comprise oligonucleotides, nucleoside diphosphates, 5'- and 3'-nucleoside monophosphates, nucleosides, and free bases. The majority of these products are excreted phates, nucleosides, and free bases. The majority of these products are excreted into the medium, and only small and constant amounts are kept in the pool. During carbon starvation at elevated temperatures, mutants deficient in ribonuclease I do not form oligonucleotides and 3'-nucleoside monophosphates, and mutants that contain a modified form of polynucleotide phosphorylase do not accumulate nucleoside diphosphates. 5'-Nucleoside monophosphates do accumulate, however, in a mutant containing thermoabile ribonuclease II, under conditions where more than 95% of all enzyme activity had been destroyed. The data presented confirm the participation of ribonuclease I and polynucleotide phosphorylase in the final steps of ribonucleic acid degradation and indicate that an exonuclease forming 5'-nucleoside monophosphates is also involved.
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PMID:Accumulation of nucleotides by starved Escherichia coli cells as a probe for the involvement of ribonucleases in ribonucleic acid degradation. 32 Jan 88

The effects of polyamines on the breakdown of synthetic polynucleotides [poly(A), poly(C), and poly(U)] by E. coli ribonuclease I [ribonucleate 3'-oligonucleotidohydrolase, EC 3.1.4.23] and ribonuclease II [EC 3.1.4.1] have been studied. The degradation of poly(C) by RNase II was stimulated by spermine and spermidine, while that of poly(A) by RNase II was not affected by polyamines. Under our standard experimental conditions, the breakdown of poly(U) by RNase II was inhibited slightly by polyamines. The stimulatory effect of spermine and spermidine on the breakdown of poly(C) occurred in the absence of monovalent cations but not in the absence of divalent cations. When polyamines were used as a stimulant of RNase II, the ratio of poly(C) degradation to poly(U) degradation was greater in the presence of inhibitors such as poly(G) than in their absence. Although the breakdown of all synthetic polynucleotides by RNase I was stimulated by polyamines, the degree of stimulation by polyamines was in the order poly(C)greater than poly(A)(see text)poly(U). However, the difference in degree of stimulation among polynucleotides decreased as monovalent cation concentration was increased.
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PMID:Effects of polyamines on the activities of Escherichia coli ribonuclease I and II. 32 40

Exonuclease activity in an Escherichia coli K12 mutant S296 is less than 1% of that in the wild type strain (Nikolaev et al., 1976). Another mutant N464 has thermolabile ribonuclease II (Castles and Singer, 1968; Kuwano et al., 1969). Genetic analysis of these mutants by Hfr conjugation and P1 transduction indicates that the structural gene (rnb) for ribonuclease II is located near the pyrF gene (28 min on the E. coli genetic map of Bachmann, Low and Taylor (1976)), and the most probable gene order is tyrT-trp-pyrF-rnb.
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PMID:Genetic analysis of mutations affecting ribonuclease II in Escherichia coli. 32 98


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