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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)

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.
Mol Gen Genet 1976 Mar 22
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).
Mol Gen Genet 1976 Mar 22
PMID:Consequences of losing ribonuclease III on the Escherichia coli cell. 77 91

"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.
Mol Gen Genet 1976 Aug 02
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.
Mol Gen Genet 1976 Dec 08
PMID:Revertants from RNase III negative strains of Escherichia coli. 79 80

Using lambda phage clones containing segments of the Escherichia coli K12 chromosome as hybridization probes, we found one gene at 42 min on the E. coli chromosome map, the expression of which was affected by RNase III. The sequence of the DNA fragment containing this gene (gen-165) revealed the presence of an open reading frame encoding a polypeptide of 165 amino acid residues. The amino acid sequence deduced from the nucleotide sequence exhibited a remarkable similarity to that of the human ferritin H chain.
Mol Gen Genet 1991 Mar
PMID:Cloning and sequencing of an Escherichia coli K12 gene which encodes a polypeptide having similarity to the human ferritin H subunit. 201 45

The synthesis of Escherichia coli polynucleotide phosphorylase (PNPase) was examined in a mutant strain defective in the RNA processing enzyme RNase III (Rnc-). We found that the specific activity and the synthesis rate of PNPase were increased in the Rnc- strain by more than three times that in an Rnc+ strain. Such increased synthesis of PNPase was not observed in a mutant strain transformed with a plasmid carrying the rnc+ gene. Quantitative analysis of RNA showed that the transcripts from the pnp gene, which encodes PNPase, were degraded more slowly in the Rnc- strain than in the Rnc+ strain. These results indicate that processing of the transcripts by RNase III is intimately involved in controlling the expression of pnp by affecting the stability of its messenger RNA.
Mol Gen Genet 1987 Aug
PMID:RNA processing by RNase III is involved in the synthesis of Escherichia coli polynucleotide phosphorylase. 282 71

Stability of RNA was tested in strains of Escherichia coli carrying single, double, or triple mutations in the RNA processing enzymes RNase III, RNase E and RNase P. Tests were carried out for total pulse labeled RNA, beta-galactosidase mRNA and for the decay of preexisting RNA during carbon starvation. Decay of RNA was measured at permissive and nonpermissive temperatures, and in no case were significant differences between mutants and non-mutant strains found. Therefore, we conclude that the three processing enzymes; RNase III, E and P do not contribute significantly to turnover of RNA IN Escherichia coli.
Mol Gen Genet 1980 Jan
PMID:Decay of RNA in RNA processing mutants of Escherichia coli. 615 28

The Schizosaccharomyces pombe temperature-sensitive mutant snm1 maintains reduced steady-state quantities of the spliceosomal small nuclear RNAs (snRNAs) and the RNA subunit of the tRNA processing enzyme RNase P. We report here the isolation of the pac1+ gene as a multi-copy suppressor of snm1. The pac1+ gene was previously identified as a suppressor of the ran1 mutant and by its ability to cause sterility when overexpressed. The pac1+ gene encodes a double-strand-specific ribonuclease that is similar to RNase III, an RNA processing and turnover enzyme in Escherichia coli. To investigate the essential structural features of the Pac1 RNase, we altered the pac1+ gene by deletion and point mutation and tested the mutant constructs for their ability to complement the snm1 and ran1 mutants and to cause sterility. These experiments identified four essential amino acids in the Pac1 sequence: glycine 178, glutamic acid 251, and valines 346 and 347. These amino acids are conserved in all RNase III-like proteins. The glycine and glutamic acid residues were previously identified as essential for E. coli RNase III activity. The valines are conserved in an element found in a family of double-stranded RNA binding proteins. Our results support the hypothesis that the Pac1 RNase is an RNase III homolog and suggest a role for the Pac1 RNase in snRNA metabolism.
Mol Gen Genet 1995 Jun 25
PMID:Rescue of the fission yeast snRNA synthesis mutant snm1 by overexpression of the double-strand-specific Pac1 ribonuclease. 761 61

The rnc-97 mutation of the Escherichia coli double-stranded-RNA-specific ribonuclease III (RNAaseIII) was previously isolated by virtue of the lethal expression of RNAaseIII in Saccharomyces cerevisiae. Here we show that rnc-97 is a single point mutation causing the substitution of glycine 97 by glutamic acid. The mutation eliminates the lethal phenotype of RNAaseIII expression in yeast and reduces fourfold the effect of RNAaseIII expression on bacteriophage gy1 propagation in E. coli. Mutant RNAaseIII-G97E and wild-type RNAaseIII were purified according to published procedures. The apparent molecular masses of the two enzymes on SDS polyacrylamide gels are the same but they differ in pI (6.85 for RNAaseIII-G97E and 7.3 for RNAaseIII). Whereas the two enzymes (under standard assay conditions) do not show a great difference in activity towards double-stranded RNA and defined single-stranded RNAaseIII substrates, they differ dramatically (20-fold or more) under conditions of Mg2+ limitation. The hypothesis that limitation of Mg2+ ions in vivo is responsible for the phenotypes of the rnc-97 mutation in S. cerevisiae and E. coli is discussed.
J Gen Microbiol 1993 Apr
PMID:Characterization of the rnc-97 mutation of RNAaseIII: a glycine to glutamate substitution increases the requirement for magnesium ions. 851 31

The importance of Lactococcus lactis biovar diacetylactis (L. diacetylactis) in the dairy industry is due to its ability to produce aroma compounds, such as acetoin and diacetyl, from citrate. The first step in citrate utilization is its uptake by the cells. In L. diacetylactis, the citrate transport system is encoded by the citQRP operon. We have previously proposed that expression of citQRP operon is regulated at the post-transcriptional level. In this paper, we show that the cit mRNA is processed at a complex secondary structure in L. diacetylactis and Escherichia coli. This secondary structure includes the 5'-terminal two-thirds of citQ and the overlap between citQ and citR. Primer-extension analysis revealed that the major cleavage sites are located upstream of citR and within citQ. In an attempt to identify the enzyme(s) responsible for this cleavage, we have analyzed this processing in E. coli mutants deficient in endoribonucleases. A comparative analysis of cit mRNA degradation was performed in RNase E and RNase III mutants and in wild-type strains using Northern blot hybridization. This analysis revealed that the cit transcript is degraded into several breakdown products, which are significantly stabilized in the mutant lacking RNase III. Our results indicate that the complex secondary structure has a critical role in the control of the expression of cit mRNA. A model for processing is discussed.
Mol Gen Genet 1998 Apr
PMID:RNA processing is involved in the post-transcriptional control of the citQRP operon from Lactococcus lactis biovar diacetylactis. 961 67


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