Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.8 (polynucleotide phosphorylase)
 723 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The reduction of nucleic acid by an endogenous polynucleotide phosphorylase and ribonuclease in cells of Brevibacterium JM98A (ATCC 29895) was studied. A simple process was developed for the activation of the endogenous RNA-degrading enzyme(s). RNA degradation was activated by the presence of Pi with 14.2 mumol of ribonucleoside 5'-monophosphate per g of cell mass accumulating extracellularly. The optimum pH for degradation of RNA was 10.5 and the optimum temperature was 55 to 60 degrees C. Enzymatic activity was inhibited by the presence of Ca2+, Zn2+, or Mg2+. Although some of the RNA-degrading enzymatic activity was associated with the ribosomal fraction, most was soluble. Both polynucleotide phosphorylase and ribonuclease activities were identified.
 ...
PMID:Reduction of endogenous nucleic acid in a single-cell protein. 3 4

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.
 ...
PMID:A novel oligoribonuclease of Escherichia coli. I. Isolation and properties. 24 Aug 24

The inhibitory properties of poly(A) on human spleen ribonuclease have been investigated. Hydrolytic activity has been shown to be strongly inhibited by poly(A) contained within RNAs isolated from a variety of natural sources. Furthermore, poly(A) segments of varying length have been covalently linked at the 3' terminus of Escherichia coli 5 S rRNA by polynucleotide phosphorylase in an attempt to construct an in vitro demonstration of the stabilization of RNA which contains poly(A). The extent to which these poly(A) tracts, varying from 4 to 132 nucleotides in length, could inhibit endonucleolytic attack on the 5 S rRNA to which they are linked was found to be dependent upon their length and upon small changes in spermidine concentration. The consequences of these findings are discussed in terms of a possible role for poly(A).
 ...
PMID:Stabilization of an RNA molecule by 3'-terminal poly (A)-induced inhibition of RNase activity. 77 65

The kinetics of 3H-uridine incorporation into measles-infected Vero cells demonstrated that maximum virus-specific RNA synthesis occurred between 16 and 20 h after infection. Sedimentation analysis on sucrose gradients revealed the presence of four species of RNA having sedimentation coefficients 4S, 12 to 26S, 28 to 36S and 50S. Annealing studies showed that RNA sedimenting in the 12 to 36S regions was 100% complementary in base sequence to nucleocapsid 50S RNA, and at least 96% of the 50S genomic RNA was transcribed during virus replication. Polynucleotide binding experiments ane ribonuclease treatment indicated that poly(A) sequences were associated with the intracellular 12 to 26S, 28 to 36S and 50S RNAs. Denaturation of intracellular 50S RNA followed by sucrose gadient centrifugation demonstrated that this was a mixture of genomic 50S and heterogeneous RNAs which sedimented at 4 to 40S. The genomic RNA did not contain poly(A) sequences, and these are presumably associated with the heterogeneously sedimenting RNAs. The size of poly(A) sequences present on the 12 to 36S RNAs was estimated to be in the range of 70 to 140 nucleotides. Treatment of the 12 to 36S RNAs and their poly(A) sequences with polynucleotide phosphorylase indicated that the poly(A) was located on the 3' end of the RNAs, but that under the experimental conditions used this was protected by the secondary structure of the molecules.
 ...
PMID:Rolyadenylic acid [poly(A)] sequences associated with measles virus intracellular ribonucleic acid (RNA) species. 88 16

We have used a photoreactive cross-linking reagent, poly(A/8-N3-A) (a poly(A) of average molecular mass of 100 kDa in which 5-10% of the A residues are replaced by 8-N3-A), to label poly(A) binding proteins of rat liver nuclear envelopes. This reagent was prepared by polymerizing a mixture of ADP and 8-N3-ADP with polynucleotide phosphorylase. The purified poly(A) was labeled in the 5'-position with a 32P group. In nuclear envelopes prepared by a low salt DNase I procedure, the poly(A/8-N3-A) labeled a protein-nucleic acid complex of approximately 270 kDa, which on degradation with RNase U2 or NaOH at pH 10 yielded two polypeptides of approximately 50 and 30 kDa. These photoreaction products were markedly decreased when resealed nuclear envelopes or non-nuclear envelope proteins were irradiated in the presence of poly(A/8-N3-A). The affinity labeling was intensified when resealed vesicles were made leaky by freezing or ultrasonication, suggesting that the poly(A) binding proteins are accessible from the nucleoplasmic but not the cytoplasmic face of the envelope. Moreover binding was specific for poly(A). Alternative reagents, random poly(A/8-N3-A,C,G,U) of about 100 kDa and poly(dA) (molecular mass between 350 and 515 kDa), showed a very low affinity for poly(A) recognition proteins in the low salt DNase I-treated nuclear envelopes; the 270-kDa band was labeled only weakly. The binding site was not protected by poly(A,C,G,U), weakly by poly(dA), and distinctly by poly(A).
 ...
PMID:Poly(A) binding proteins located at the inner surface of resealed nuclear envelopes. 169 Nov 70

The rapid synthesis and breakdown of mRNA in prokaryotes can impose a significant energy drain on these cells. Previous in vivo studies [Duffy, J. J., Chaney, S. G. & Boyer, P. D. (1972) J. Mol. Biol. 64, 565-579; Chaney, S. G. & Boyer, P. D. (1972) J. Mol. Biol. 64, 581-591] indicated that while RNA turnover in Escherichia coli was hydrolytic, it was nonhydrolytic in Bacillus subtilis. Here we provide an explanation for these observations based on enzymatic analysis of extracts of these two organisms. RNA degradation to the mononucleotide level in E. coli extracts is due solely to two active ribonucleases, RNase II and polynucleotide phosphorylase, which act hydrolytically and phosphorolytically, respectively. RNase II activity represents close to 90% of the total activity of the extract, as expected for predominantly hydrolytic degradation in this organism. In contrast, RNase II is absent from B. subtilis extracts, and the primary mode of RNA degradation is phosphorolytic, employing the Bacillus equivalent of polynucleotide phosphorylase and releases nucleoside diphosphates as products. A low level of a Mn2(+)-stimulated, hydrolytic ribonuclease is also detectable in B. subtilis extracts. Overall, E. coli and B. subtilis extracts differ by about 20- to 100-fold, depending on the substrate, in their relative use of hydrolytic and phosphorolytic routes of RNA degradation. The relation of the mode of mRNA degradation to the environment of the cell is discussed.
 ...
PMID:Enzymatic basis for hydrolytic versus phosphorolytic mRNA degradation in Escherichia coli and Bacillus subtilis. 170 36

Although polyadenylation has commonly been regarded as a special feature of eukaryotic messenger RNA, there are many reports of polyA tails on bacterial RNA (for example, refs 3-8). In Escherichia coli, adenylation mediated by the pcnB gene greatly accelerates decay of RNA I, an antisense repressor of replication of ColE1 type plasmids that resembles highly structured transfer RNA but shows the rapid turnover characteristic of mRNA. Here we report that both 3' adenylation and 5' phosphorylation affect the rate of digestion of RNA I by the 3' exonuclease, polynucleotide phosphorylase; conversely, mutation of the polynucleotide phosphorylase-encoding pnp gene affects ribonuclease acting at the 5' end. Together these findings indicate that enzymes attacking RNA I at its separate termini can interact functionally. Additionally, our discovery that adenylation-mediated degradation by polynucleotide phosphorylase imparts an mRNA-like half-like to RNA I suggests a possible mechanism to account for the rapid decay of mRNA in E. coli.
 ...
PMID:RNA degradation in Escherichia coli regulated by 3' adenylation and 5' phosphorylation. 753 64

In Escherichia coli, ribonuclease E (RNase E) is a key endonuclease in mRNA decay. We have analysed the role of E coli RNase E on the degradation of a heterologous cytochrome c3 (cyc) mRNA from Desulfovibrio vulgaris Hildenborough. The decay of the cyc transcript in wild-type and mutant E coli cells was followed and the degradation intermediates analysed by Northern blotting and S1 protection analysis. The half-life of total cyc mRNA intermediates was increased in the RNase E mutant. A number of degradation intermediates were stabilised, and new species arose. However, some species decayed faster in the met5 mutant at the non-permissive temperature, suggesting that RNase E might inhibit their degradation. The results indicate that RNase E is involved in cyc mRNA degradation, and, interestingly, decay of certain intermediates could be reduced by this enzyme activity. This may suggest a functional interaction between RNase E and exonucleases, like polynucleotide phosphorylase.
 ...
PMID:RNase E can inhibit the decay of some degradation intermediates: degradation of Desulfovibrio vulgaris cytochrome c3 mRNA in E coli. 887 97

The degradation process of the rpsO mRNA is one of the best characterised in E coli. Two independent degradation pathways have been identified. The first one is initiated by an RNase E endonucleolytic cleavage which allows access to the transcript by polynucleotide phosphorylase and RNase II. Cleavage by RNase E gives rise to an rpsO message lacking the stabilising hairpin of the primary transcript; this truncated mRNA is then degraded exonucleolytically from its 3' terminus. This pathway might be coupled to the translation of the message. The second pathway allows degradation of polyadenylated rpsO mRNA independently of RNase II, PNPase and RNase E. The ribonucleases responsible for degradation of poly(A) mRNAs under these conditions are not known. Poly(A) tails have been proposed to facilitate the degradation of structured RNA by polynucleotide phosphorylase. In contrast, we believe that removal of poly(A) by RNase II stabilises the rpsO mRNA harbouring a 3' hairpin. In addition to these two pathways, we have identified endonucleolytic cleavages which occur only in strains deficient for both RNase E and RNase III suggesting that these two endonucleases protect the 5' leader of the mRNA from the attack of unidentified ribonuclease(s). Looping of the rpsO mRNA might explain how RNase E bound at the 5' end can cleave at a site located just upstream the hairpin of the transcription terminator.
 ...
PMID:Multiple degradation pathways of the rpsO mRNA of Escherichia coli. RNase E interacts with the 5' and 3' extremities of the primary transcript. 891 31

The effect of Escherichia coli ribonuclease II and polynucleotide phosphorylase was analysed on the degradation of Desulfovibrio vulgaris cytochrome c3 (cyc) mRNA. In the absence of these exoribonucleolytic activities, cyc mRNA was stabilised but the two enzymes had a different role in its decay. Surprisingly, a temperature-sensitive mutation in ribonuclease II gave a degradation pattern similar to what had been observed in the absence of endoribonuclease E activity. In an RNase II deletion mutant this was not observed. We propose and verify a model in which the temperature-sensitive ribonuclease II interferes with the action of ribonuclease E.
 ...
PMID:A new role for RNase II in mRNA decay: striking differences between RNase II mutants and similarities with a strain deficient in RNase E. 897 85


1 2 3 4 5 Next >>