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:3.1.13.1 (exoribonuclease)
732 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An enzyme, purified 300-fold from Escherichia coli infected with bacteriophage T4, catalyzes the conversion of 5'-termini of polyribonucleotides to internal phosphodiester bonds. The reaction requires ATP and Mg(++). For every 5'-(32)P terminus rendered resistant to alkaline phosphatase, an equal amount of AMP and PPi are formed. Various polyribonucleotides are substrates in the reaction; to date, the best substrate is [5'-(32)P]polyriboadenylate. With the latter substrate, no evidence of intermolecular reaction was obtained. However, the 5'-(32)P termini of poly(A) rendered resistant to alkaline phosphatase are also resistant to attack by RNase II, polynucleotide phosphorylase, and low concentrations of venom phosphodiesterase. Since the product formed with poly(A) lacks 3'-hydroxyl ends, as measured with these exonucleases, the enzyme appears to convert linear molecules of polyriboadenylate to a circular form by the intramolecular covalent linkage of the 5'-phosphate end to the 3'-hydroxyl terminus.
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PMID:Purification and properties of bacteriophage T4-induced RNA ligase. 434 72

The location of poly(A) sequences in the RNA of mammalian RNA-tumor viruses was determined by enzymatic analyses. The 56-64S viral genomic RNAs, the 20-40S viral subunit RNAs, and the 4-5S poly(A) sequences excised from these viral RNAs were subjected to either hydrolysis with a 3'-OH specific exoribonuclease from Ehrlich ascites tumor cells or phosphorolysis from the 3'-termini with polynucleotide phosphorylase from Micrococcus luteus. Purified adenosine-labeled poly(A) fragments, excised from genomic viral RNAs by RNase A and T(1) digestion, were hydrolyzed with the 3'-OH specific exoribonuclease for various periods of time. Poly(U) filter binding studies of the residual poly(A) indicated that 97% of the poly(A) fragments were hydrolyzed. Adenosine-labeled genomic and subunit viral RNAs and excised poly(A) fragments were phosphorolyzed from their 3'-termini for various periods of time with polynucleotide phosphorylase. The degree of phosphorolysis was monitored by poly(U) filter binding studies, and CCl(3)COOH insolubility and solubility determinations. There was an initial preferential rate of phosphorolysis of the poly(A) sequences of genomic and subunit viral RNAs as compared to the total adenosine-labeled viral RNAs. The data from these two different enzymatic mechanisms of action indicated conclusively that the poly(A) sequences were located at the 3'-termini of genomic and subunit viral RNAs.
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PMID:Polyriboadenylate sequences at the 3'-termini of ribonucleic acid obtained from mammalian leukemia and sarcoma viruses. 437 12

For the simultaneous determining of several enzymes of nucleic acid metabolism during polynucleotide phosphorylase isolation TLC was used. It was found that using TLC one can simultaneously detect six and more enzymes, e. g. polynucleotide phosphorylase, 5'-nucleotidase, exoribonuclease together with nucleosidediphosphatase, desaminase etc. The method is simple and accessible.
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PMID:[Use of a TLC method for the simultaneous determination of an enzyme complex of nucleic acid metabolism during the isolation of polynucleotide phosphorylase]. 620 91

A 7.1 kb HindIII-XhoI fragment of E. coli DNA which contains the structural gene for ribonuclease II (rnb) has been cloned in the recombinant plasmid pDK24. At least two constitutively expressed genes are encoded on the fragment as shown by maxicell analysis. On denaturing polyacrylamide gels RNase II appears as a single 72,000 dalton species. The approximate site of transcription initiation of the rnb gene has been mapped. Although derivatives of E. coli harboring pDK24 contained 10-fold more RNase II activity that wild type strains without the plasmid, the degradation rate of mRNA was similar in all strains tested. Strains deficient in both RNase II and polynucleotide phosphorylase appear inviable.
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PMID:Amplification of ribonuclease II (rnb) activity in Escherichia coli K-12. 633 77

We have used an in vitro Escherichia coli tRNA processing system to investigate the specific role of individual exoribonucleases in the 3' maturation of tRNA precursors. The processing of pre-tRNA(Tyr)su3+ and pre-tRNA(2Arg) was studied using extracts from cells lacking one or multiple exoribonucleases or using purified RNases. Earlier genetic studies had suggested that multiple exoribonucleases contributed to the maturation of tRNA precursors, and this was proven directly in the studies described here. Complete 3' processing required the combined action of multiple exoribonucleases, and each RNase showed distinct specificities for maturation of the different parts of the 3' precursor segment. RNase II and polynucleotide phosphorylase were most effective in shortening long 3' trailer sequences to intermediates with 2-4 extra 3' residues. Final trimming of the last few 3' nucleotides of these precursors was carried out most efficiently by RNases T and PH, but the two enzymes differed in their specificity for individual nucleotide positions. Depending on the tRNA precursor, the relative importance of the various RNases to the overall maturation process differed. We also showed that purified exoribonucleases can completely complement mutant extracts and that tRNA maturation can be totally reconstructed in vitro using purified enzymes. These studies provide the first detailed information about the specific role of individual exoribonucleases in tRNA processing, and bring us closer to defining a complete E. coli tRNA maturation pathway.
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PMID:The role of individual exoribonucleases in processing at the 3' end of Escherichia coli tRNA precursors. 750 97

Polynucleotide phosphorylase, a 3' to 5' processive exoribonuclease is post-transcriptionally autocontrolled and it was previously shown that this control is dependent on a 5' processing by RNase III. In this paper, the mechanism of regulation is analyzed by studying the properties of a pnp-lacZ translational gene fusion. It is shown that this message is stable, even when processed by RNase III, and that the degradation rate is directly linked to the intracellular concentration of polynucleotide phosphorylase or to the pnp-lacZ messenger translation rate. Mutations able to decrease the level of repression are all located in the ribosome loading site. Taken together, these results suggest that polynucleotide phosphorylase is able to recognize specifically the processed messenger and to prevent its translation, thus allowing degradation of the message.
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PMID:Polynucleotide phosphorylase of Escherichia coli induces the degradation of its RNase III processed messenger by preventing its translation. 751 Mar 92

The Escherichia coli rpsO gene gives rise to different mRNA species resulting either from termination of transcription or from processing of primary transcripts by RNase E and RNase III. The main degradation pathway of these transcripts involves a rate-limiting RNase E cleavage downstream of the structural gene which removes the 3' terminal stem-loop structure of the transcription terminator. This structure protects the message from the attack of 3'-5' exonucleases and its removal results in very rapid degradation of the transcript by polynucleotide phosphorylase and RNase II. Polynucleotide phosphorylase is also able to degrade slowly the mRNA harboring the 3' terminal hairpin of the terminator. In contrast, RNase II appears to protect the rpsO mRNA species which retains the 3' hairpin structure. Rapid degradation of the rpsO mRNA is observed after inactivation of RNase II even in a strain deficient for RNase E and polynucleotide phosphorylase. The enzyme(s) involved in this degradation pathway is not known. We detected an unstable elongated rpsO mRNA presumably resulting from the addition of nucleotides at the 3' end of the transcript.
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PMID:Roles of RNase E, RNase II and PNPase in the degradation of the rpsO transcripts of Escherichia coli: stabilizing function of RNase II and evidence for efficient degradation in an ams pnp rnb mutant. 751 47

RNA-OUT, the 69-nucleotide antisense RNA that regulates Tn10/IS10 transposition folds into a simple stem-loop structure. The unusually high metabolic stability of RNA-OUT is dependent, in part, on the integrity of its stem-domain: mutations that disrupt stem-domain structure (Class II mutations) render RNA-OUT unstable, and restoration of structure restores stability. Indeed, there is a strong correlation between the thermodynamic and metabolic stabilities of RNA-OUT. We show here that stem-domain integrity determines RNA-OUT's resistance to 3' exoribonucleolytic attack: Class II mutations are almost completely suppressed in Escherichia coli cells lacking its principal 3' exoribonucleases, ribonuclease II (RNase II) and polynucleotide phosphorylase (PNPase). RNase II and PNPase are individually able to degrade various RNA-OUT species, albeit with different efficiencies: RNA-OUT secondary structure provides greater resistance to RNase II than to PNPase. Surprisingly, RNA-OUT is threefold more stable in wild-type cells than in cells deficient for RNase II activity, suggesting that RNase II somehow lessens PNPase attack on RNA-OUT. We discuss how this might occur. We also show that wild-type RNA-OUT stability changes only two-fold across the normal range of physiological growth temperatures (30-44 degrees C) in wild-type cells, which has important implications for IS10 biology.
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PMID:Decay of the IS10 antisense RNA by 3' exoribonucleases: evidence that RNase II stabilizes RNA-OUT against PNPase attack. 753 7

As part of our genetic analysis of mRNA decay in Escherichia coli K-12, we examined the effect of the pcnB gene [encoding poly(A) polymerase I] on message stability. Eliminating poly(A) polymerase I (delta pcnB) dramatically stabilized the lpp, ompA, and trxA transcripts. The half-lives of individual mRNAs were increased in both a delta pcnB single mutant and a delta pcnB pnp-7 rnb-500 rne-1 multiple mutant. We also found mRNA decay intermediates in delta pcnB mutants that were not detected in control strains. By end-labeling total E. coli RNA with [32P]pCp and T4 RNA ligase and then digesting the RNA with RNase A and T1, we showed that many RNAs in a wild-type strain contained poly(A) tails ranging from 10 nt to > 50 nt long. When polynucleotide phosphorylase, RNase II, and RNase E were absent, the length (> 100 nt) and number (10- to 20-fold) of the poly(A) tails increased. After transcription initiation was stopped with rifampicin, polyadenylylation apparently continued. Deleting the structural gene for poly(A) polymerase I (pcnB) reduced the amount of 3'-terminal poly(A) sequences by > 90%. We propose a model for the role of polyadenylylation in mRNA decay.
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PMID:Polyadenylylation helps regulate mRNA decay in Escherichia coli. 789 80

Oligoribonuclease, an exoribonuclease specific for small oligoribonucleotides, was initially characterized 20 years ago (S. K. Niyogi and A. K. Datta, J. Biol. Chem. 250:7307-7312, 1975) and shown to be different from RNase II and polynucleotide phosphorylase. Here we demonstrate, using mutant strains and purified enzymes, that oligoribonuclease is not a manifestation of RNases D, BN, T, PH, and R, exoribonucleases discovered subsequently. Thus, oligoribonuclease is the eighth distinct exoribonuclease discovered in Escherichia coli. We also show that oligoribonuclease copurifies with polynucleotide phosphorylase.
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PMID:Oligoribonuclease is distinct from the other known exoribonucleases of Escherichia coli. 760 90


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