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)

Transmission electron microscopy was used to examine active ribosomal ribonucleic acid (rRNA) genes in two strains of Escherichia coli: N2077, deficient in the enzyme responsible for proper cleavage of the 16S sequence from the elongating nascent rRNA transcript; and N2076, functional in ribonuclease (RNase) III activity, yet otherwise isogenic to N2077. In the strain with wild-type RNase III, double gradients corresponding to a pattern of 16S-cleavage-23S transcription were observed. However, the RNase III-deficient strain exhibited a single ribosomal gradient of approximately the same length as the combined 16S-23S gradients of the wild-type strain. When the rRNA genes were somewhat loosely packed with RNA polymerases, a few of the nascent chains in the ribosomal matrixes of the RNase III-deficient strain were cleaved, but most appeared to be unprocessed. The completed, uncleaved transcripts originating from these gradients are believed to be 30S rRNA molecules recently characterized by biochemical probes.
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PMID:Visualization of ribosomal ribonucleic acid synthesis in a ribonuclease III-Deficient strain of Escherichia coli. 33 50

In vitro transcription of T3 DNA by T3 phage-induced RNA polymerase (nucleosidetriphosphate:RNA nucleotidyltransferase; EC 2.7.7.6) yields eight discrete RNAs (designated I-VIII) with molecular weights of approximately 6.2, 4.7, 4, 2.8, 1.8, 0.9, 0.52, and 0.21 X 10(6), respectively. Comparison of the size of in vitro T3 RNA polymerase transcripts with in vivo late T3 mRNAs indicates that several late RNAs produced in T3-infected cells do not correspond to any of the in vitro RNAs, and no RNAs as large as the three largest in vitro RNA species, I, II, and III, are observed. Escherichia coli RNase III cleaves these three high molecular weight T3 RNA polymerase transcripts to discrete RNAs that comigrate in polyacrylamide gel electrophoresis with some of the late T3 RNAs.
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PMID:Ribonuclease III cleavage of bacteriophage T3RNA polymerase transcripts to late T3 mRNAs. 33 3

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

Mutants of Escherichia coli deficient in ribonuclease III are nonmotile. All transductants and revertants that regained ribonuclease III also regained motility, and all transductants that remained or became rnc are nonmotile, although only some of the revertants that regained motility also became ribonuclease III+.
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PMID:Ribonuclease III is involved in motility of Escherichia coli. 34 82

The size of lysozyme mRNA from T7-infected E. coli RNase III+ and RNase III- strains was analyzed by sucrose gradient sedimentation, dimethylsulfoxide (Me2SO) sucorse gradient sedimentation, and preparative gel electrophoresis. Each technique revealed a similar size distribution of multiple lysozyme mRNA's. Analysis by preparative gel electrophoresis of RNA extracted after infection of Escherichia coli Bst (RNase III+) separated lysozyme mRNA into six peaks of activity ranging in size from 0.2 x 10(6) to 1.9 x 10(6) daltons. Four well-resolved major peaks of activity were detected, having apparent molecular weights of approximately 0.61 x 10(6), 0.76 x 10(6), 0.92 x 10(6), and 1.3 x 10(6). A broad band of activity, with a molecular weight range from 0.2 x 10(6) to 0.37 x 10(6), was also present, and a sixth peak of activity was sometimes observed that migrates with a mobility corresponding to a molecular weight of 1.9 x 10(6). Judging from their molecular weight as estimated by electrophoresis, most, if not all, of the lysozyme mRNA's were polycistronic. The RNA extracted after infection of an RNase III- host contained a more heterogeneous collection of lysozyme mRNA's. In addition to lysozyme mRNA activity on RNAs with molecular weights between 0.2 x 10(6) and 1.9 x 10(6), RNA species with molecular weights estimated at 4 x 10(6) to 5 x 10(6) were also detected. The data indicate that RNase III processes at least some of the primary lysozyme transcripts. The multiple lysozyme mRNA's represent discrete RNA species rather than aggregates because analysis of the size of lysozyme mRNA under completely denaturing conditions, in Me2SO, produced a similar size distribution of lysozyme mRNAs. Also, treatment of RNA with 90% Me2SO, which separates the strands of a completely double-stranded RNA, did not significantly alter the electrophoretic mobility of the lysozyme mRNA.
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PMID:Effect of RNase III on the size of bacteriophage T7 lysozyme mRNA. 35 3

RNase III had no positive effect on the translation of bacteriophage T7 lysozyme mRNA in vivo or in vitro. The time of appearance and quanity of lysozyme in T7-infected E. coli BL107, an RNase III- strain, and T7-infected E. coli BL15, a nearly isogenic RNase III+ strain, were indistinguishable. Nearly identical patterns of lysozyme mRNA activity were obtained when RNA extracted at different times after infection of RNase III+ and RNase III- hosts was translated in cell-free extracts of E. coli containing or lacking RNase III. Exposure of RNA extracted from T7-infected E. coli BL107 (RNase III-) to purified RNase III did not increase the lysozyme mRNA activity of this RNA. The only result that implied that RNase III has a differential effect on the translatability of the lysozyme mRNA was the translation of fractionaed RNA from T7-infected E. coli BL107. Translation of the smallest and largest lysozyme messages, 0.33 x 10(6) and 4 x 10(6) to 5 x 10(6) daltons, was the most inefficient in RNase III- cell-free extracts as compared to RNase III+ cell-free translation. The translation of the most abundant, medium-sized lysozyme mRNA between 0.9 x 10(6) and 1.5 x 10(6) daltons was the least affected by the absence of RNase III. The existence of a lag between the appearance of lysozyme mRNA and the appearance of lysozyme in T7 infection was confirmed. In these studies a very rapid method of RNA extraction was used, eliminating the possibility of continued RNA transcription during cell collection and RNA extraction. With this method of analysis, the length of the lag period was established at about 3 min. The possibility that RNase III is the controlling element of the lag period was eliminated by these investigations.
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PMID:Effect of RNase III on efficiency of translation of bacteriophage T7 lysozyme mRNA. 35 4

The nucleotide sequence of Escherichia coli DNA at both ends of the gene for 16S rRNA has been determined for two rRNA operons, rrnD and rrnX. The 400 nucleotides we have examined exhibit only one base change between rrnD and rrnX. Within the 160 nucleotides that precede mature 16S rRNA sequences are cleavage sites for several E. coli endonucleases, including RNase III. A 240-nucleotide segment encompassing the 16S 3' end contains another RNase III site and the point of presumed RNase P scission at the 5' end of tRNA1Ile, the first tRNA appearing in the 16-23S spacer region of rrnD and rrnX. Most importantly, the DNA sequences predict that regions flanking the 16S gene in the rRNA primary transcript extensively base pair to form a double-helical structure whose hairpin loop includes the entire mature 16S molecule; within this structure is a 26-base-pair stem containing the two sequences at which RNase III action generates the 5' and 3' ends of a previously characterized precursor to 16S rRNA. Although our proposed secondary structure for this RNase III site is superficially dissimilar to previously described cleavage sites in the T7 early mRNA precursor, certain common features may constitute signals for RNase III recognition. The suggestion that distant portions of an RNA molecule can form a secondary structure within which specific endonucleolytic cleavages occur may have mechanistic implications for the joining of noncontiguous portions of gene sequences evident in several eukaryotic mRNAs.
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PMID:Complementary sequences 1700 nucleotides apart form a ribonuclease III cleavage site in Escherichia coli ribosomal precursor RNA. 35 89

To determine if proteins RNase III and rho, both of which can determine the 3' ends of RNA molecules, can complement each other, double mutants defective in these two factors were constructed. In all cases (four rho mutations tested) the double mutants were viable at lower temperatures, but were unable to grow at higher temperatures at which both of the parental strains grew. Genetic analyses suggested that the combinations of the rnc rho (RNase III-Rho-) mutations was necessary and probably sufficient to confer temperature sensitivity on carrier strains. Physiological studies showed that synthesis and maturation of rRNA, which is greatly affected by RNase III, as well as other RNAs, was indistinguishable in rnc rho strains as compared to rnc rho+ strains, thus suggesting that RNase III and rho do not complement one another in determining the 3' ends of RNA molecules. In rnc rho strains, however, the newly synthesized rRNA failed to accumulate. Thus, decay of rRNA could be the reason for the temperature sensitivity of the double mutant strains. These experiments suggest that RNase III and rho can both protect rRNA from degradation by cellular ribonucleases. They also point to the possibility that the nucleotide sequences involved in the determination of the 3' ends of RNA molecules by these two factors are not identical.
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PMID:Metabolism of ribosomal RNA in mutants of Escherichia coli doubly defective in ribonuclease III and the transcription termination factor rho. 35 8

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

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


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