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:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Replication of RNA bacteriophages in the presence of rifamycin was studied in different Escherichia coli strains that vary in RNase content but are not isogenic: AB259 RNase+, Q13 RNase I- PNPase-, AB105 RNase I- RNase III-. It was found that rifamycin did not affect characteristics of phage replication such as the general pattern of viral RNA synthesis and intracellular development of the phage. These characteristics are strain specific and independent of the cell growth rate, which defines only phage release. The inhibition of cell division by rifamycin interfered with the release of the phage and thus produced an apparent effect of rifamycin on phage replication.
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PMID:Replication of RNA bacteriophages in the presence of rifamycin. 36 77

The disappearance of ribosomes in Escherichia coli cells starved for a carbon source was studied. We used a series of mutants, some of them lacking in ribonuclease I(RNase I, EC 2.7.7.17), and other containing various combinations of modified polynucleotide phosphorylase (PNPase, EC 2.7.7.8) and modified ribonuclease II (RNase II, EC 3.1.4.1). RNA was prepared from the starved mutant cells and separated on polyacrylamide gels. The results obtained indicate that 23 S RNA degradation is similar in all strains that lack RNase I, and is slightly increased in the strain that contains this enzyme. The extent of 16 S RNA degradation is identical in all strains tested. RNA species in the size of 4 S and smaller accumulate in mutants containing modified forms of PNPase and RNase II. The appearance of an RNA species 10% smaller than 16 S RNA (d16 S RNA) was observed in all strains that contain unmodified RNase II. Analysis of ribosomes and polysomes and their RNA content indicated that polysomes are converted to monosomes and these, in turn, to ribosomal subunits. No RNA degradation products were found in polysomes, 70 S, OR 50 C particle; 30 S subunits contained 16 S RNA as well as the d16 S RNA species. Subunits are degraded to a similar extent in all strains lacking RNase I, and at a slightly faster rate in the strain that contains RNase I. The RNA to protein ratio in subunits prepared from starved cells is similar to that of unstarved cultures. Very little degradation of ribosomal proteins occurs in these mutants during carbon starvation. The proteins released from degraded ribosomes are found in the fast sedimenting (20,000 times g) pellet. Cell viability studies indicated a direct correlation between the capacity of the mutants to recovery from starvation and their capacity to degrade RNA. Thus a biological necessity for degradation of ribosomes during starvation is implied. Based on these data we propose that the endonucleolytic degradation of ribosomal RNA is the primary event in starvation degradation. It takes place in ribosomal subunits, which fall apart after the endonucleoltic attack. The RNA pieces produced by this cleavage are degraded to nucleotide by RNase II and PNPase. The ribosomal proteins attach to the cell membrane.
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PMID:The fate of ribosomes in Escherichia coli cells starved for a carbon source. 108 66

In the presence of Mg2+ ions, polynucleotide phosphorylase (PNPase, EC 2.7.7.8) is known to synthesize RNA-like polymers using ribonucleoside-5'-diphosphate (NDP) substrates but to be unable to utilize deoxyribonucleoside substrates. Our experiments show that when MgCl2 is replaced by FeCl3, PNPase becomes able to synthesize deoxyheteropolymers using deoxyribonucleoside-5'-diphosphates (dNDPs). The deoxyheteropolymer formed from the four dNDPs is degraded by pancreatic DNase, but not by RNase, and is readily used as a template by DNA-dependent DNA polymerase. Synthesis of this DNA-like polymer is accomplished de novo without the help of any primer or preexisting template. What is more, dA/dG and dC/dT ratios of polymers synthesized by different bacterial PNPases closely match ratios found in DNA of the bacterial species the enzyme came from.
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PMID:De Novo Synthesis of DNA-Like Molecules by Polynucleotide Phosphorylase In Vitro 866 1

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.
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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

Genome comparison permits identification of chromosome regions conserved during evolution. Bacillus subtilis and Escherichia coli are so distant that there exists very few conserved landmarks in their genome organisation. Analysis of the conserved cmk rpsA cluster pinpointed the importance of cytosine nucleotide metabolism. In these bacteria, mRNA turnover provides an efficient means to fulfil the need for CDP as a precursor of DNA synthesis. The cmk rpsA operon is responsible for CDP synthesis. This function is self-explained in the case of the cmk gene (which codes for cytidylate kinase). The case of rpsA, that codes for ribosomal protein S1, is more subtle. It is suggested here that S1 is a RNA-binding protein helping polynucleotide phosphorylase (PNPase, known to be phylogenetically related to S1) to degrade mRNA, or helper molecule involved in other RNase activities. This provides an explanation for the elusive function of PNPase, which generates nucleoside diphosphates (not monophosphates) when degrading RNA. This also accounts for the discovery that the B. subtilis comR gene product is PNPase. This article briefly discusses the availability of cytosine nucleotides in eukaryotes, and suggests that they are derived from phospholipids turnover. Finally, the GC content of genomes is discussed in this new light.
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PMID:Comparison between the Escherichia coli and Bacillus subtilis genomes suggests that a major function of polynucleotide phosphorylase is to synthesize CDP. 917 91

mRNA instability is an intrinsic property that permits timely changes in gene expression by limiting the lifetime of a transcript. The RNase e of Escherichia coli is a single-strand-specific endo-nuclease involved in the processing of rRNA and the degradation of mRNA. A nucleolytic multi-enzyme complex now known as the RNA degradosome was discovered during the purification and characterization of RNase E. Two other components are a 3' exoribonuclease (polynucleotide phosphorylase, PNPase) and a DEAD-box RNA helicase (RNA helicase B, RhlB). RNase E is a large multidomain protein with N-terminal ribonucleolytic activity, an RNA-binding domain and a C-terminal "scaffold" that binds PNPase, enolase and RhlB. RhlB by itself has little activity but is strongly stimiulated by its interaction with RNase E. RhlB in vitro can facilitate the degradation of structured RNA by PNPase. Since the discovery of the RNA degradosome in E. coli, related complexes have been described in other organisms.
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PMID:The Escherichia coli RNA degradosome: structure, function and relationship in other ribonucleolytic multienzyme complexes. 1203 60

In this paper we show that RNase R is a cold shock protein that is induced seven- to eightfold by cold shock and that its expression is tightly regulated by temperature. Transcriptional studies reveal that the rnr gene is co-transcribed with flanking genes as an operon induced under cold shock. The induction of RNase R levels is mainly a result of the stabilization of the rnr transcripts. The transient stability of the rnr transcripts is shown to be regulated by PNPase at the end of the acclimation phase. Studies with an rnr mutant revealed a cold-shock phenotype showing that RNase R contributes to growth at low temperatures. We have shown that RNase R can be involved in the maturation of SsrA/tmRNA, an important small stable RNA involved in protein tagging and ribosome rescue. The wide biological significance of RNase R regarding adaptation to cold shock and its involvement in RNA surveillance, protein quality control and pathogenesis is discussed.
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PMID:Cold shock induction of RNase R and its role in the maturation of the quality control mediator SsrA/tmRNA. 1462 21

When Bacillus subtilis is grown in the presence of excess tryptophan, transcription of the trp operon is regulated by binding of tryptophan-activated TRAP to trp leader RNA, which promotes transcription termination in the trp leader region. Transcriptome analysis of a B. subtilis strain lacking polynucleotide phosphorylase (PNPase; a 3'-to-5' exoribonuclease) revealed a striking overexpression of trp operon structural genes when the strain was grown in the presence of abundant tryptophan. Analysis of trp leader RNA in the PNPase(-) strain showed accumulation of a stable, TRAP-protected fragment of trp leader RNA. Loss of trp operon transcriptional regulation in the PNPase(-) strain was due to the inability of ribonucleases other than PNPase to degrade TRAP-bound leader RNA, resulting in the sequestration of limiting TRAP. Thus, in the case of the B. subtilis trp operon, specific ribonuclease degradation of RNA in an RNA-protein complex is required for recycling of an RNA-binding protein. Such a mechanism may be relevant to other systems in which limiting concentrations of an RNA-binding protein must keep pace with ongoing transcription.
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PMID:Recycling of a regulatory protein by degradation of the RNA to which it binds. 1497 55

In a continuing effort to identify ribonucleases that may be involved in mRNA decay in Bacillus subtilis, fractionation of a protein extract from a triple-mutant strain that was missing three previously characterized 3'-to-5' exoribonucleases (polynucleotide phosphorylase [PNPase], RNase R, and YhaM) was undertaken. These experiments revealed the presence of a high-molecular-weight nuclease encoded by the yhcR gene that was active in the presence of Ca(2+) and Mn(2+). YhcR is a sugar-nonspecific nuclease that cleaves endonucleolytically to yield nucleotide 3'-monophosphate products, similar to the well-characterized micrococcal nuclease of Staphylococcus aureus. YhcR appears to be located principally in the cell wall and is likely to be a substrate for a B. subtilis sortase. Zymogram analysis suggests that YhcR is the major Ca(2+)-activated nuclease of B. subtilis. In addition to having a unique overall domain structure, YhcR contains a hitherto unknown structural domain that we have named "NYD," for "new YhcR domain."
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PMID:Bacillus subtilis YhcR, a high-molecular-weight, nonspecific endonuclease with a unique domain structure. 1529 38

mRNA decay is a major determinant of gene expression. In Escherichia coli, message degradation initiates with an endoribonucleolytic cleavage followed by exoribonuclease digestion to generate 5'-mononucleotides. Although the 3' to 5' processive exoribonucleases, PNPase and RNase II, have long been considered to be mediators of this digestion, we show here that another enzyme, RNase R, also participates in the process. RNase R is particularly important for removing mRNA fragments with extensive secondary structure, such as those derived from the many mRNAs that contain REP elements. In the absence of RNase R and PNPase, REP-containing fragments accumulate to high levels. RNase R is unusual among exoribonucleases in that, by itself, it can digest through extensive secondary structure provided that a single-stranded binding region, such as a poly(A) tail, is present. These data demonstrate that RNase R, which is widespread in prokaryotes and eukaryotes, is an important participant in mRNA decay.
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PMID:An important role for RNase R in mRNA decay. 1566 99


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