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:3.1.26.3 (RNase III)
1,015 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A temperature-sensitive mutant strain was isolated from an RNase III-(rnc) strain of Escherichia coli. At the permissive temperature it behaves like the parental strain, but at the nonpermissive temperature it fails to produce normal levels of 23 S and 5 S rRNA, while instead the 25 S rRNA species becomes very prominent. (The 25 S molecule appears in rnc cells and contains 23 S rRNA sequences). When an rnc+ mutation was introduced to such a strain, or when the rnc mutation was replaced by an rnc+ allele, the strain remained temperature-sensitive. At the permissive temperature such strains synthesized rRNA like any other E. coli strain, but at the nonpermissive temperature they remained unable to synthesize normal levels of 5 S rRNA, and instead a larger molecule was accumulated. The simplest interpretation of theses findings is that the mutant strain contains a temperature-sensitive processing endoribonuclease, RNase E, which normally introduces a cut in the growing rRNA chain somewhere between the 23 S and the 5 S rRNA cistrons. These findings help also to explain the nature and origin of the various rRNA species observed in RNase III- cells and add to our understanding of processing of ribosomal RNA in normal cells of Escherichia coli.
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PMID:A conditional lethal mutant of Escherichia coli which affects the processing of ribosomal RNA. 34 28

Temperature-sensitive mutants were isolated from an rnc (RNase III-) strain of Escherichia coli, and their rRNA metabolism was analyzed on 3% polyacrylamide gels. One of these mutants was unable to produce 23S and 5S rRNAs at the nonpermissive temperature. When an rnc+ allele was introduced to this strain, it remained temperature sensitive. At the nonpermissive temperature, this strain could then produce 23S rRNA but was unable to make normal levels of 5S rRNA. In matings and transduction experiments, the defect in rRNA metabolism and temperature sensitivity behaved as a syndrome caused by a single point mutation, which was mapped at min 23.5 on the E. coli chromosome. This mutation probably affects an enzyme, ribonuclease E (RNase E), which introduces a cut in the nascent rRNA transcript between the 23S and the 5S rRNA cistrons. The mutation rne is recessive with respect to temperature sensitivity and the pattern of rRNA. Revertants able to grow at 43 degrees and with normal metabolism of rRNA were isolated; genetic analysis showed that they do not contain the original rne mutation, suggesting that they were true revertants. By combining the rne mutation with an rnc mutation, double rnc rne strains were synthesized, which behaved very similarly to the original rnc strain from which the rne mutation was isolated. Such strains have RNA metabolism that is similar to that of rnc strains at permissive temperatures, but at the nonpermissive temperature they fail to synthesize p23, m23, and 5S rRNAs. Thus, the experiments reported here, together with previous studies, suggest the existence of a new processing ribonuclease activity in Escherichia coli, which is called ribonuclease E.
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PMID:Isolation, genetic mapping and some characterization of a mutation in Escherichia coli that affects the processing of ribonuleic acid. 36 43

1. A precursor to small stable RNA, 10Sa RNA, accumulates in large amounts in a temperature sensitive RNase E mutant at non-permissive temperatures, and somewhat in an rnc (RNase III-) mutant, but not in an RNase P- mutant (rnp) or wild type E. coli cells. 2. Since p10Sa RNA was not processed by purified RNase E and III in customary assay conditions, we purified p10Sa RNA processing activity about 700-fold from wild type E. coli cells. 3. Processing of p10Sa RNA by this enzyme shows an absolute requirement for a divalent cation with a strong preference for Mn2+ over Mg2+. Other divalent cations could not replace Mn2+. 4. Monovalent cations (NH+4, Na+, K+) at a concentration of 20 mM stimulated the processing of p10Sa RNA and a temperature of 37 degrees C and pH range of 6.8-8.2 were found to be optimal. 5. The enzyme retained half of its p10Sa RNA processing activity after 30 min incubation at 50 degrees C. 6. Further characterization of this activity indicated that it is RNase III. 7. To further confirm that the p10Sa RNA processing activity is RNase III, we overexpressed the RNase III gene in an E. coli cells that lacks RNase III activity (rnc mutant) and RNase III was purified using one affinity column, agarose.poly(I).poly(C). 8. This RNase III preparation processed p10Sa RNA in a similar way as observed using the p10Sa RNA processing activity purified from wild type E. coli cells, confirming that the first step of p10Sa RNA processing is carried out by RNase III.
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PMID:Characterization of the RNA processing enzyme RNase III from wild type and overexpressing Escherichia coli cells in processing natural RNA substrates. 137 63

We have established that the long non-coding intercistronic region of the dicB operon of Escherichia coli expresses a trans-acting division inhibitor specified by a region dicF, at most 65 nucleotides-long. The present study deals with the processing of dicBF operon mRNA in vivo, and identifies the dicF gene product as a 53 nucleotide RNA species. A sequence at the end of DicF resembles, and behaves as, a Rho-independent terminator, but further processing of readthrough transcripts, presumably by RNase III, followed by a limited 3' to 5' degradation, appears to generate additional DicF-RNA 3' ends. For the 5' end of DicF-RNA, our results show that a 190 nucleotide precursor DicF-RNA species is formed by cleavage at an RNase III site, while the 53 nucleotide minimal DicF-RNA is generated by further processing requiring the presence of an active form of RNase E in vivo. These data indicate that an untranslated product derived from an operon RNA can have a regulatory activity by affecting cell division.
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PMID:Escherichia coli cell division inhibitor DicF-RNA of the dicB operon. Evidence for its generation in vivo by transcription termination and by RNase III and RNase E-dependent processing. 169 Dec 99

The transcripts of the rpsO-pnp operon of Escherichia coli, coding for ribosomal protein S15 and polynucleotide phosphorylase, are processed at four sites in the 249 nucleotides of the intercistronic region. The initial processing step in the decay of the pnp mRNA is made by RNase III, which cuts at two sites upstream from the pnp gene. The other two cleavages are dependent on the wild-type allele of the rne gene, which encodes the endonucleolytic enzyme RNase E. The cuts are made 37 nucleotides apart at the base of the stem-loop structure of the rho-independent attenuator located downstream from rpsO. The cleavage downstream from the attenuator generates an rpsO mRNA.nearly identical with the monocistronic attenuated transcript, while the cleavage upstream from the transcription attenuator gives rise to an rpsO mesage lacking the terminal 3' hairpin structure. The rapid degradation of the processed mRNA in an rne+ strain, compared to the slow degradation of the transcript that accumulates in an rne- strain, suggests that RNase E initiates the decay of the rpsO message by removing the stabilizing stem-loop at the 3' end of the RNA.
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PMID:Decay of mRNA encoding ribosomal protein S15 of Escherichia coli is initiated by an RNase E-dependent endonucleolytic cleavage that removes the 3' stabilizing stem and loop structure. 170 67

We recently showed that RNase III can process a small stable RNA, precursor 10Sa RNA, that accumulates in an rne (RNase E) strain at non-permissive temperatures. Precursor 10Sa (p10Sa) RNA is processed to 10Sa RNA in two steps, the first step is catalyzed by RNase III in the presence of Mn2+ but not Mg2+. It was shown that RNase III cosediments with membrane preparation from wild type as well as RNase III overexpressing cells. However, the possibility of membrane preparation contamination with ribosomes could not be ruled out. Here we show that RNase III, E and P are not associated with ribosomes. E. coli cells were opened either by alumina grinding or by sonication and fractionated into cytosolic and pellet fractions. The characterization of membrane preparations was done by assaying NADH oxidase, a bona fide membrane enzyme. Ribosomes prepared by alumina grinding were found to be contaminated with small fragments of membrane which contained RNase III activity. RNase III and NADH oxidase activities were present in the ribosomal preparations which could be solubilized by reagents that dissolve the inner membrane. Isopycnic sucrose gradient centrifugation of the membrane and ribosomal preparations also confirmed that RNase III fractionated with the inner membrane. Similarly RNase P activity was found in the corresponding fractions when isopycnic centrifugation of membrane and ribosome preparations was carried out. RNase E activity was also found to be present mostly in the post-ribosomal supernatant. These findings show that RNase III, E and P are not ribosomal enzymes.
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PMID:RNA processing enzymes RNase III, E and P in Escherichia coli are not ribosomal enzymes. 172 76

Cells overexpressing the RNA-processing enzymes RNase III, RNase E and RNase P were fractionated into membrane and cytoplasm. The RNA-processing enzymes were associated with the membrane fraction. The membrane was further separated to inner and outer membrane and the three RNA-processing enzymes were found in the inner membrane fraction. By assaying for these enzymatic activities we showed that even in a normal wild-type strain of Escherichia coli these enzymes fractionate primarily with the membrane. The RNA part of RNase P is found in the cytosolic fraction of cells overexpressing this RNA, while the overexpressed RNase P protein sediments with the membrane fraction; this suggests that the RNase P protein anchors the RNA catalytic moiety of the enzyme to a larger entity. The implications of these findings for the cellular organization of the RNA-processing enzymes in the cell are discussed.
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PMID:Location of the RNA-processing enzymes RNase III, RNase E and RNase P in the Escherichia coli cell. 194 11

The splice junction sequence of td mRNA from T4-infected cells has been determined (5'....GGU-CUA....3') and shown to be identical to that of the RNA ligation product encoded by the cloned gene [Belfort et al. Cell 41 (1985) 375-382]. The RNA processing functions, T4 RNA ligase, T4 polynucleotide kinase, and the host prr gene product appear not to be essential for exon ligation; neither are the host endoribonucleases RNase III, RNase P and RNase E required for intron excision. While these results are consistent with the autocatalytic splicing mechanism demonstrated in vitro [Chu et al. J. Biol. Chem. 260 (1985) 10680-10688], they leave unanswered the question of which protein(s), if any, might stimulate the in vivo reaction. Analysis of the products of the cloned td gene has led to identification of two td-encoded polypeptides, namely a polypeptide corresponding to the exon-I-coding sequence (NH2-TS), and the catalytically active thymidylate synthase (TS). Kinetic and nucleotide sequence data provide evidence that NH2-TS is the product of the primary transcript and that TS is encoded by spliced mRNA. These results suggest that splicing may provide a switch controlling the relative expression of NH2-TS and TS, two proteins with markedly different temporal appearances despite their identical transcriptional and translational start sites.
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PMID:RNA splicing and in vivo expression of the intron-containing td gene of bacteriophage T4. 242 90

The secondary structure of the 9S RNA precursor to ribosomal 5S RNA in Escherichia coli has been determined using chemical reagents and ribonucleases in combination with a reverse transcription procedure. The 9S RNA precursor was generated in vitro by T7 RNA polymerase, and the rrnB operon terminator, T1, was able to terminate the in vitro transcript. The secondary structure model exhibits three structural domains corresponding to a 5' region, a mature region and a terminator region. The mature domain is structurally identical to 5S RNA, and the ribosomal proteins L18 and L25 are able to bind to the precursor. The processing endoribonuclease RNase E cleaves between the structural domains. Moreover, an intramolecular refolding of the nascent transcript must take place if the current view of RNase III processing stems is correct.
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PMID:The 9S RNA precursor of Escherichia coli 5S RNA has three structural domains: implications for processing. 304 57

The bla and ompA gene transcripts were used as substrates to probe Escherichia coli extracts for ribonucleolytic activities. A site specific endoribonucleolytic activity was identified that cleaves ompA and bla mRNA. The cleavages occur in vitro and in vivo. For both the bla and ompA mRNA most of the cleavage sites which were identified map in the 5' non-coding region. The cleavages of the ompA transcript have been previously suggested to regulate the growth rate dependent stability of this mRNA. Thus we propose that the identified endoribonucleolytic activity may be involved in the degradation of mRNA. Analysis of mutants revealed that the cleavages are mediated by endonucleases which do not seem to be identical to RNase III, RNase E or RNase P.
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PMID:In vivo and in vitro identity of site specific cleavages in the 5' non-coding region of ompA and bla mRNA in Escherichia coli. 304 39


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