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)

T7 early mRNA's are generated from a high-molecular-weight precursor RNA by site-specific RNase III cleavage. When T7 DNA is transcribed in vitro by Escherichia coli RNA polymerase, the transcript is a large, single-piece RNA equivalent to the in vivo precursor RNA. The T7 RNA synthesized in vitro can be translated as a polycistronic messenger without cleavage by RNase III. All T7 early proteins are synthesized in an RNase III-free, protein-synthesizing system directed by the uncleaved T7 RNA.
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PMID:Translation of T7 RNA in vitro without cleavage by RNase III. 77 30

1. New high molecular weight RNA species have been found in an RNase III deficient mutant of E. coli. These RNA's were very minor but stable components of the cells, and their molecular weights, which range from 3-5.5 million daltons, are higher than that of 30S precursor ribosomal RNA. In these respects these RNAs are similar to the 2.5 M RNA reported previously (Yuki and Wittmann, 1974). 2. A method to analyse minor RNA components is described. A linear relationship between logarithms of molecular weights and logarithms of distance moved in 1.5-7.5% polyacrylamide concentration gradient gels is also described in this report. 3. DNA species whose molecular weights ranged from 1.8 to 5.5 million daltons and also a species of 8 million daltons are described. two techniques commonly used to identify RNA, viz. DNase treatment and labeling with radioactive uridine, are discussed in connection with these DNAs. 4. The determination of the molecular weight of 30S precursor ribosomal RNA is discussed and it is suggested that this RNA is heterogenous, consisting of two species of molecular weight 1.8 million daltons and 2.0 million daltons, respectively.
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PMID:Detection of ribonucleic acids which are larger than 30S precursor ribosomal RNA in RNase III deficient E. coli cells. 77 88

An isogenic pair of Escherichia coli strains, one carrying an rnc+ and the other an rnc- allele (a mutation which reduces the level of ribonuclease III), was compared. The rnc- strain fails to grow at very elevated temperatures (for E. coli) while the rnc+ strain does grow exponentially. Assaying the residual RNase III like activity in extracts of the rnc- strain at different pHs and at different temperatures suggested that this residual RNase III like activity is not due to RNase III. This raised the possibility that the rnc- strain is devoid of any RNase III activity in the cell. Comparing the decay of newly synthesized RNA and functional decay of beta-galactosidase mRNA in such strains revealed that in both strains these parameters proceed in similar rates, which suggests that RNase III is not involved in the metabolism of mRNA. During carbon starvation preexisting total RNA, as well as 23S and 16S rRNA, decay faster in the rnc- strain, thus eliminating the possibility that RNase III is the endoribonuclease which initiates the decay of rRNA during starvation (Kaplan and Apirion, 1975a).
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PMID:Consequences of losing ribonuclease III on the Escherichia coli cell. 77 91

T4 Species I RNA, a molecule 140 nucleotides in length with some structural features very much like a tRNA, is specifically cleaved by an enzymatic activity in Escherichia coli extracts to give three segments with 19, 48 and 73 nucleotides. We report the purification and characterization of the E. coli RNase which cleaves two 3' phosphodiester bonds of T4 Species I RNA. This reaction has many properties in common with those catalyzed by E. coli RNase III, although the optimal salt conditions for T4 Species I RNA cleavage differ significantly from those for other RNase III-catalyzed reactions. The reaction is not catalyzed by extracts from an E. coli strain lacking RNase III activity. Furthermore, T4 Species I RNA is cleaved by highly purified E. coli RNase III to yield the same three specific fragments. We conclude that this specific cleavage is due to the action of RNase III, and that the requirement for lower ionic strength may reveal further important properties about this RNA processing enzyme.
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PMID:Cleavage of T4 species I ribonucleic acid by Escherichia coli ribonuclease III. 78 26

The structure, synthesis, and post-transcriptional modifications of 23-S and 16-S ribosomal RNAs (rRNAs) have been studied in the facultatively parasitic bacterium, Bdellovibrio bacteriovorus. The mature 23-S and 16-S type of rRNAs in Bdellovibrio are larger than the analogous molecules in Escherichia coli by at least 1.0 - 10(5) and 0.5 - 10(5) daltons, respectively, and have a conformation different from E. coli rRNAs as judged by relative electrophoretic mobilities in polyacrylamide gels with and without denaturing conditions. Studies on the kinetics of synthesis and maturation of ribosomal RNA in Bdellovibrio show that precursor forms analogous to p23-S and p16-S in E. coli are synthesized. In addition, some earlier precursor rRNAs in Bdellovibrio are seen that appear analogous to the 25S and 17.5-S pre-rRNAs that have only been observed in the RNAase III deficient mutant of E. coli strain AB301-105 (Nikolaev, Birenbaum, M. and Schlessinger, D. (1975) Biocheim, Biophys. Acta 395, 478-489). These early precursor stages have not been observed in other procaryotic species, including E. coli that have normal levels of RNAase III. The results from the Bdellovibrio system provide that the 25-s and 17.5-S pre-rRNAs are normal stages of rRNA modification and are part of a multiple step maturation process, and therefore are not aberrations associated with the RNase III deficient mutation.
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PMID:Structure, synthesis, and post-transcriptional modification of ribosomal ribonucleic acid in Bdellovibrio bacteriovorus. 79 72

"SPACER" SEQUENCES OF AN RRNA gene transcript were detected with high efficiency by hybridization with DNA of the specilized transducing phase phi80rrn. Hybridization-competition studies revealed that 20 to 23% of the 30S precursor rRNA, obtained from E. coli mutant strain AB301/105, consist of "spacer" sequences. The "spacer" sequences formed hybrids with E. coli DNA, but not with Vibrio DNA. Experiments with RNA labeling in the presence of rifampicin showed that more than 80% of the spacer sequences arrive in full-length 30S pre rRNA chains before any cleavage of the RNA occurs. The hybridization assays also permitted the detection of "spacer" sequences in pulse-labeled rRNA of wild-type cells, in which the 30S pre-rRNA is already cleaved during its synthesis. Many of these "spacer" sequences degraded to alcohol-soluble materials with a half-life time of 1.2 min. The half-life was not lengthened by the treatment of cells with chloramphenicol, which stabilizes bulk mRNA. However, unstable "spacer" sequences transcribed in cells deficient in RNase III exhibited slower degradation, with a half-life time of about 9 min, whereas the cleavage of 30S pre-rRNA to smaller RNA species occurred with a half-life of about 3 min. These results are consistent with the notion that a rate-limiting action of RNase III in the initial attack leads to degradation of "spacer" sequences in rRNA gene transcript; and that degradation is not at all connected with ribosome translocation.
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PMID:Stability of "spacer" sequences of pre-ribosomal RNA in Escherichia coli. 79 93

E. coli strains carrying the rnc-105 allele do not show any level of RNase III in extracts, grow slower than rnc+ strains at temperatures up to 45 degrees C and fail to grow at 45 degrees C. Revertants which can grow at 45 degrees C were isolated. The vast majority of them still do not grow as fast as rnc+ strains and did not regain RNase III activity. The mutation(s) which caused them are suppressor mutations (physiological suppressors) which do not map in the immediate vicinity of the rnc gene. A few of the revertants regain normal growth, and contain normal levels of RNase III. They do not harbor the rnc-105 allele and therefore are considered to be true revertants. By using purines other than adenine it was possible to isolate rnc + pur- revertants from an rnc- pur- strain with relative ease. They behaved exactly like the true rnd+ revertants isolated from rns- strains at 45 degrees C. A merodiploid strain which contains the rnc+ gene on an episome behaves exactly like an rnc+ strain with respect to growth and RNA metabolis, eventhough its specific RNase III activity is about 60% of that of an rnc+ strain; thus the level of RNase III is not limiting in the cell. The rnc- strains show a characteristic pattern of transitory molecules, related to rRNA, 30S, 25S, "p23" and 18S, which are not observed in rnc+ strains. This pattern is unchanged in rnc- strains and in the revertants which are still lacking RNase III, regardless of the temperature in which RNA synthesis was examined (30 degrees to 45 degrees C). On the other hand, in the rnc+ strains as well as in the true revertants and the rnc+/rnc- merodiploid, the normal pattern of p16 and p23 is observed at all temperatures. These findings suggest that all the effects observed in RNase III- strains are due to pleiotropic effects of the rnc-105 allele, and that the enzyme RNase III is not essential for the viability of the E. coli cell.
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PMID:Revertants from RNase III negative strains of Escherichia coli. 79 80

Double-stranded RNAs from Penicillium chrysogenum virus have been treated with RNAse III, pancreatic RNAse A and RNAse T1 and the degradation of the RNAs has been studied under different conditions. It was found that only the two former enzymes cut across both strands, RNase T1 cannot cleave double strands. RNase III was shown to digest double-stranded RNA by a two step process: an initial phase of specific cleavage is followed by random degradation. In the first phase the enzyme exhibited a definite preference for some specific base pattern. Partial or complete degradation with pancreatic RNase A could also be achieved in media with high salt concentration provided that the enzyme: substrate ratio was increased together with the salt concentration. By combining different assay techniques, the process of degradation was followed from the early stages to complete digestion and the breakdown products were characterised. It is suggested that a structural change in the enzyme molecules enables them to act on double-stranded RNA. RNAse T1, being unable to cleave double strands, provides a useful tool for studying the secondary structure of RNA molecules. Treatment with different nucleases yielded some new information on the structure of different RNA species in Penicillium stoloniferum virus.
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PMID:Action of nucleases on double-stranded RNA. 81 98

A RNase from calf thymus, which specifically cleaves native or synthetic double-stranded RNA molecules endonucleolytically, has been isolated and purified from calf thymus. For optimal activity, the enzyme requires a sulfhydryl reagent and divalent cations; over 95 per cent of the activity is inhibited by 0.5 mm ethidium bromide. The degradation of [3H]poly(C)-poly(I) by purified enzyme preparations yields labeled dinucleotides and octanucleotides; the latter oligonucleotide contained 5'-phosphate and 3'-hydroxyl termini. The enzyme cleaves high molecular weight RNAs such as RNA products formed in vitro by T3 phage-induced RNA polymerase from T3 phage DNA, heterogeneous RNA isolated from duck reticulocyte nuclei, and 45 S RNA isolated from rat liver nucleoli. The mode of degradation of RNA in vitro with the double-stranded RNase is similar to that of Escherichia coli RNase III and appears to act endonucleolytically. The degradation of 45 S RNA with the enzyme results in the production of 29 S and 19 S RNA fragments. These findings suggest that the enzyme may be involved in the processing of high molecular weight precursor RNAs to mRNA or rRNAs in a manner analogous to that reported for RNase III of E. coli.
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PMID:Isolation and purification of double-stranded ribonuclease from calf thymus. 83 40

Ribonuclease III from Escherichia coli has been purified to apparent homogeneity by affinity chromatography on immobilized double-stranded RNA. Polyacrylamide gel electrophoresis of the purified enzyme in the presence of sodium dodecyl sulfate gave one band of protein with a molecular weight of approximately 25,000. Chromatography on Sephadex G-100 is consistent with a molecular weight of 50,000, suggesting that the native enzyme is a dimer. RNase III cuts some single-stranded RNAs, such as bacteriophage T7 early RNA, at specific sites in vivo. This RNA is cut as these same sites by the purified enzyme under all conditions tested. However, at low ionic strength relatively small increases in enzyme concentration produce cuts as secondary sites. At high ionic strength, the enzyme's preference for the sites cut in vivo is more pronounced and secondary cuts are made only at very high enzyme concentrations. Secondary cuts are shown to occur at specific sites and are made in a variety of RNAs even from sources other than E. coli. By cutting RNAs at secondary sites it should be possible to generate RNA fragments which would be useful in a number of studies.
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PMID:RNase III cleavage of single-stranded RNA. Effect of ionic strength on the fideltiy of cleavage. 93 8


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