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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 new ribonuclease has been isolated from Escherichia coli. The enzyme is present in the 100,000 times g supernatant fraction and has been purified over 200-fold. Studies of the enzyme reveal that: 1. The enzyme shows a marked preference for oligoribonucleotides; indeed, the reaction rate is inversely proportional to the chain length of the substrate. The enzyme does not attack polynucleotides even at high concentrations of enzyme and has no detectable DNase activity. 2. The enzyme is stimulated strongly by Mn2+, less strongly by Mg2+, and not at all by Ca2+ and monovalent cations. 3. The enzyme is purified free of RNase I, RNase II, RNase III, polynucleotide phosphorylase, and other known ribonucleases of E. coli. The enzyme displays identical properties when isolated from mutants of E. coli that are deficient in the above ribonucleases. 4. The enzyme has a marked thermostability, a point of further distinction from RNase II.
J Biol Chem 1975 Sep 25
PMID:A novel oligoribonuclease of Escherichia coli. I. Isolation and properties. 24 Aug 24

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.
Genetics 1978 Sep
PMID:Metabolism of ribosomal RNA in mutants of Escherichia coli doubly defective in ribonuclease III and the transcription termination factor rho. 35 8

An in vitro replication system has been used to study the control of DNA replication of the relaxed plasmids Col E1 and RSF1030. An RNA transcript approximately 100 nucleotides long is synthesized during the in vitro DNA replication reaction. This RNA is synthesized approximately 450 bp away from the origin of replication. A small insertion in the coding sequence for the RNA made from Col E1 DNA leads to a larger RNA species and simultaneously to an increase in plasmid copy number. Revertants missing the specific insertion show shorter RNA transcripts and wild-type copy number. Although plasmids Col E1 and RSF1030 have no extensive sequence homology, the RNA synthesized during RSF1030 replication has almost the same mobility as the Col E1 RNA on polyacrylamide gels and hybridizes to the Col E1 origin region. Extracts prepared from mutants of Escherichia coli deficient in ribonuclease III do not replicate RSF1030 or Col E1 plasmids in vitro. When supplemented with homogeneous RNAase III, such extracts do support DNA replication on these templates, indicating that RNAase III is required for DNA replication. We propose that the 100 nucleotide RNA species is involved in regulating the initiation of DNA replication of these plasmids, and that RNAase III may be involved in processing this RNA.
Cell 1979 Sep
PMID:Role of plasmid-coded RNA and ribonuclease III in plasmid DNA replication. 38 34

Heterogeneous nuclear RNA (hnRNA) from HeLa cells contains intramolecular duplexes. Since hnRNA is associated with protein in vivo, it is possible that the double-stranded regions observed in deproteinized hnRNA form spontaneously upon the release of protein from single-stranded but potentially complementary sequences. We show here that this is not the case for a class of double-stranded sequences that is defined by resistance to RNases A + T(1) at high ionic strength. Exposure of HeLa hnRNA.ribonucleoprotein (hnRNP) particles to Escherichia coli RNase III, a double-strand-specific endoribonuclease, destroys most of the sequences resistant to RNases A + T(1). This effect is completely blocked when hnRNP is exposed to RNase III in the presence of an excess of purified double-stranded RNA. In addition, we show that there exist two classes of double-stranded RNA in hnRNP at a salt concentration of 0.13 M. These are distinguished by their relative resistance to RNases A + T(1). The more stable double-stranded sequences, which are resistant to RNases A + T(1) at 0.13 M, comprise 1.0-1.1% of the nucleotides in hnRNP. The less stable double-stranded sequences comprise an additional 1.5-2.0% of the nucleotides in hnRNP. These are sensitive to RNase III at 0.13 M, but are not resistant to RNases A + T(1) unless the salt concentration is raised to 0.63 M. The demonstration that double-stranded sequences resistant to RNases A + T(1) exist in native ribonucleoprotein and are not artifacts of deproteinization now makes it appropriate to seriously consider their possible functional role in hnRNA metabolism, perhaps as binding sites for regulatory proteins involved in mRNA processing.
Proc Natl Acad Sci U S A 1977 Sep
PMID:Secondary structure of heterogeneous nuclear RNA: two classes of double-stranded RNA in native ribonucleoprotein. 41 25

We reported earlier that the addition of double-stranded RNA and ATP increases the endonuclease activity more in an extract of Ehrlich ascites tumor cells which have been treated with an interferon preparation than in a comparable extract from control cells. We report here that the addition of double-stranded RNA to an extract from Ehrlich ascites tumor cells which have been treated with an interferon preparation [or with the interferon inducer poly(I)-poly(C)] promotes the phosphorylation by [gamma-32P]ATP of at least two proteins: P1 (molecular weight of 64,000) and P2 (molecular weight of 37,000). Double-stranded RNA also promotes the phosphorylation of at least one (i.e., P1) of these two proteins in an extract from cells which have not been treated with interferon, but the extent of phosphorylation is much smaller. Double-stranded RNA which has been degraded by RNase III, or DNA, does not promote the phosphorylation.
Proc Natl Acad Sci U S A 1976 Sep
PMID:Interferon, double-stranded RNA, and protein phosphorylation. 106 6

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.
Biochem Int 1991 Sep
PMID:RNA processing enzymes RNase III, E and P in Escherichia coli are not ribosomal enzymes. 172 76

Bacteriophage lambda int gene expression is regulated differentially from transcripts originated at the pL and pI promoters. Transcripts initiated at pI terminate at the site tI and express int gene product efficiently. Polymerases starting at pL do not terminate at tI, due to the antiterminating activity of lambda N protein. The pL transcripts are unable to express Int protein efficiently because sib, a control site overlapping tI in the unterminated RNA, is processed by host RNase III. We have isolated lambda sib- mutants by their inability to inhibit int expression from pL transcripts. sib mutations were genetically mapped to the left of the lambda attachment site, and do not structurally alter this site for recombination. Several sib mutations do alter the nucleotide sequence of the overlapping sib and tI sites. The lambda sib- mutants tested prevent RNA processing but do not affect transcription termination in vivo.
J Mol Biol 1986 Sep 05
PMID:Mutations of bacteriophage lambda that define independent but overlapping RNA processing and transcription termination sites. 294 21

The bacteriophage lambda cIII gene product regulates the lysogenic pathway by stabilizing the lambda cII regulatory protein. Our results show that the expression of the lambda cIII gene is subject to specific requirements. Tests of a set of cIII-lacZ gene and operon fusions reveal that a sequence upstream of the cIII ribosome binding site is needed for cIII translation. The sequence contains an inefficient RNase III processing site. Furthermore, expression of cIII is drastically reduced in cells lacking RNase III. We have isolated a phage carrying a mutation (r1), which lies in the upstream sequence, that leads to a reduction in cIII translation and inactivates the RNase III processing site. The r1 mutant is nevertheless still dependent on RNase III for cIII translation; r1 reduces cIII translation by a factor of 3 in wild-type cells and by a factor of approximately equal to 30 in an RNase III mutant host. We propose that RNase III stimulates cIII translation by binding to the upstream sequence and thereby exposing the cIII ribosome binding site. This stimulation does not involve RNA cleavage. Consistent with this hypothesis is our finding that, in vitro, unprocessed cIII mRNA is translated, whereas RNase III-cleaved cIII mRNA is not.
Proc Natl Acad Sci U S A 1987 Sep
PMID:RNase III stimulates the translation of the cIII gene of bacteriophage lambda. 295 96

The RNA polymerases encoded by bacteriophages T3 and T7 have similar structures, but exhibit nearly exclusive template specificities. We have determined the nucleotide sequence of the region of T3 DNA that encodes the T3 RNA polymerase (the gene 1.0 region), and have compared this sequence with the corresponding region of T7 DNA. The predicted amino acid sequence of the T3 RNA polymerase exhibits very few changes when compared to the T7 enzyme (82% of the residues are identical). Significant differences appear to cluster in three distinct regions in the amino-terminal half of the protein. Analysis of the data from both enzymes suggests features that may be important for polymerase function. In particular, a region that differs between the T3 and T7 enzymes exhibits significant homology to the bi-helical domain that is common to many sequence-specific DNA binding proteins. The region that flanks the structural gene contains a number of regulatory elements including: a promoter for the E. coli RNA polymerase, a potential processing site for RNase III and a promoter for the T3 polymerase. The promoter for the T3 RNA polymerase is located only 12 base pairs distal to the stop codon for the structural gene.
Nucleic Acids Res 1985 Sep 25
PMID:Sequence and analysis of the gene for bacteriophage T3 RNA polymerase. 390 58

Transcription of the Caulobacter crescentus phage phi Cd1 genome requires both the host RNA polymerase and a phage-encoded, rifampicin-resistant RNA polymerase. Transcription of the early region of the phi Cd1 genome was examined in vitro with C. crescentus RNA polymerase. Four transcripts, A, B, C, and D, which ranged in size from 2.9 X 10(6) to 0.53 X 10(6) daltons, were synthesized in vitro by the holoenzyme. Transcript A appeared to be the major transcript since (a) it was the size of the entire 20% of the genome shown in vivo to code for the early phage mRNA, (b) it was one of the first transcripts synthesized at low enzyme-to-DNA molar ratios, and (c) it was synthesized in approximately 3 times the molar equivalent observed for the other transcripts. The A transcript initiated primarily with GTP although a portion was also labeled with ATP. The B, C, and D transcripts were present in equivalent molar ratios, were all smaller than transcript A, and were found to yield RNase III digestion products that were subsets of each other as well as of transcript A. Each of these transcripts proved to be a de novo transcript since (a) each could be pulse labeled during the initial 20 s of the reaction and (b) each transcript contained a triphosphate at its 5' terminus. Evidence is presented that suggests that the B and C transcripts initiate at or near the major A promoter but terminate at different termination or pause sites within the early region of the phage genome. Transcript D appears to initiate at a minor promoter within the terminally redundant region of the genome preceding the A promoter.
Biochemistry 1982 Sep 14
PMID:In vitro transcription of the early region of Caulobacter phage phi Cd1 deoxyribonucleic acid by host RNA polymerase. 629 89


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