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)

Examination of double mutants lacking one of the exoribonucleases, RNase II, RNase D, RNase BN, or RNase R, and also devoid of tRNA nucleotidyltransferase has suggested that none of these RNases participates in the end-turnover of tRNA. This prompted a search for and identification of a new exoribonuclease, termed RNase T. RNase T could be detected in mutant Escherichia coli strains lacking as many as three of the known exoribonucleases, and it could be separated from each of the four previously described RNases. RNase T is optimally active at pH 8-9 and requires a divalent cation for activity. The enzyme is sensitive to ionic strengths greater than 50 mM and is rapidly inactivated by heating at 45 degrees C. Its preferred substrate is tRNA-C-C-[14C]A, with much less activity shown against tRNA-C-C. RNase T is an exoribonuclease that initiates attack at the 3' hydroxyl terminus of tRNA and releases AMP in a random mode of hydrolysis. The possible involvement of RNase T in end-turnover of tRNA and in RNA metabolism in general are discussed.
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PMID:Ribonuclease T: new exoribonuclease possibly involved in end-turnover of tRNA. 637 42

The nucleotide sequence of the 5'-terminal oligonucleotides produced by pancreatic RNase digestion of bacteriophage T3 RNA polymerase (EC 2.7.7.6) transcripts of T3 DNA has been determined. The sequence determination is based upon a simple isolation procedure for the 5'-terminal oligonucleotides. This procedure involves treatment of pancreatic RNase digests of alpha 32P-labeled T3 RNA polymerase transcripts with bovine brain exoribonuclease to remove oligonucleotides with free 5'-hydroxyl termini and then chromatographing the products on hydroxylapatite to resolve the remaining oligonucleotides having 5'-phosphate termini. By application of standard two-dimensional separation and sequence techniques, the major 5'-end sequences deduced were pppGpGpGpApGpApGpApY(Y = pyrimidine nucleoside) and pppGpGpGpApGpApCp. In addition, the sequences of other minor 5'-terminal oligonucleotides observed on homochromatograms were also determined. The sequences of these 5'-oligonucleotides were pppGpGpGpApApCpY, pppGpGpGpApApUpY, pppGpGp(2-4 Gp, 2-3 ApGp)..., and pppGpGpGp.... These results demonstrate that T3 phage-induced RNA polymerase possesses a high degree of specificity in the initiation of RNA chains.
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PMID:Isolation and sequence determination of 5'-terminal oligonucleotide fragments of RNA transcripts synthesized by bacteriophage T3-induced RNA polymerase from T3 DNA. 693 43

Some early T4 ribonucleic acids were not found in an infected ribonuclease II-deficient strain but were formed in ribonuclease II+ transductants as well as in wild-type Escherichia coli.
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PMID:Altered bacteriophage T4 ribonucleic acid metabolism in a ribonuclease II-deficient mutant of Escherichia coli. 698 8

In quail oviducts the rate of synthesis of avidin, the biological end-point marker for the molecular events caused by progesterone, decreases with age. The cause of the reduced capacity of avidin induction has been studied on the molecular biological level polyadenylation of RNA which is one step in the process of post-transcriptional modification of heterogeneous nuclear RNA resulting in the formation of functional mRNA molecules. This novel approach was biochemically possible after the discovery of the poly(A) anabolic enzyme (poly(A) polymerase) and the two poly(A) catabolic enzymes (endoribonuclease IV and 5'-exoribonuclease). These enzymes are involved in the synthesis and degradation of the poly(A) segment of mRNA in vitro and most likely also in poly(A) metabolism in intact cell systems. Enzymatically controlled poly(A) metabolism of mRNA is regulated by the following interrelations: poly(A)-associated proteins and endoribonuclease IV; labilizing factor and poly(A)-associated proteins; 5'-exoribonuclease in cooperation with endoribonuclease IV and poly(A) polymerase. A close correlation between high levels of poly(A) catabolic enzymes and low rate of protein synthesis which was established in cell culture systems, seems also to be partially the biochemical cause for the reduced avidin synthesis in aging quail oviduct.
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PMID:Age-dependent gene induction in quail oviduct X. Alterations on the post-transcriptional level (enzymic aspect). 720 15

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

The maturation of 5S RNA in Escherichia coli is poorly understood. Although it is known that large precursors of 5S RNA accumulate in mutant cells lacking the endoribonuclease-RNase E, almost nothing is known about how the mature 5' and 3' termini of these molecules are generated. We have examined 5S RNA maturation in wild-type and single- or multiple-exoribonuclease-deficient cells by Northern blot and primer-extension analysis. Our results indicate that no mature 5S RNA is made in RNase T-deficient strains. Rather, 5S RNA precursors containing predominantly 2 extra nucleotides at the 3' end accumulate. Apparently, these 5S RNAs are functional inasmuch as mutant cells are viable, growing only slightly slower than wild type. Purified RNase T can remove the extra 3' residues, showing that it is directly involved in the trimming reaction. In contrast, mutations affecting other 3' exoribonucleases have no effect on 5S RNA maturation. Approximately 90% of the 5S RNAs in both wild-type and RNase T- cells contain mature 5' termini, indicating that 5' processing is independent of RNase T action. These data identify the enzyme responsible for generating the mature 3' terminus of 5S RNA molecules and also demonstrate that a completely processed 5S RNA molecule is not essential for cell survival.
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PMID:The tRNA processing enzyme RNase T is essential for maturation of 5S RNA. 754 80


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