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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)

The metY gene coding for a minor form of the initiator tRNA is the first gene of a complex polycistronic operon also encoding the transcription termination factor NusA and the translation initiation factor IF2. The mixed tRNA-mRNA polycistronic transcript is cleaved by RNase III in a hairpin structure downstream from the tRNA. This cleavage separates the tRNA from the mRNA and initiates the rapid degradation of the 5' extremity of the downstream mRNA. Dissociation of the structural (tRNA) and informational (mRNA) RNAs from this operon is also achieved by independent transcription in vivo. The presence of two transcription terminators located downstream from metY produces a small tRNAMetf2 precursor transcript, whereas an internal promoter situated between metY and the first open reading frame directs the transcription of only the protein-coding part of the operon.
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PMID:Cleavage by RNase III in the transcripts of the met Y-nus-A-infB operon of Escherichia coli releases the tRNA and initiates the decay of the downstream mRNA. 248 Oct 42

Expression of the int gene of bacteriophage lambda from two promoters, pI and pL, is differentially regulated through RNA processing. Efficient Int protein synthesis from the pL RNA is inhibited by the action of sib, a cis-acting retroregulator downstream from the int gene. We have used mapping procedures with nuclease S1 to study the pL transcripts produced in vivo after phage lambda infection. We have found an RNase III-dependent processing site within the Int coding sequence, 387 nucleotides upstream from the site of the primary cleavage by RNase III at Sib. This secondary processing site is located at the most stable region of secondary structure in the sib int region, as predicted by computer analysis. We suggest that RNase III cleavage at the Sib site allows processive exonucleolytic degradation of the RNA to proceed to a region of secondary structure within the Int coding sequence, which protects the upstream region of the transcript from further degradation.
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PMID:Retroregulation of the bacteriophage lambda int gene: limited secondary degradation of the RNase III-processed transcript. 252 18

RNase III, an Escherichia coli double-stranded endoribonuclease, is known to be involved in maturation of rRNA and regulation of several bacteriophage and Escherichia coli genes. Clones of the region of the E. coli chromosome containing the gene for RNase III (rnc) were obtained by screening genomic libraries in lambda with DNA known to map near rnc. A phage clone with the rnc region was randomly mutagenized with a delta Tn10 element, and the insertions were recombined onto the chromosome, generating a series of strains with delta Tn10 insertions in the rnc region. Two insertions that had Rnc- phenotypes were located. One of them lay in the rnc gene, and one was in the rnc leader sequence. Polarity studies showed that rnc is in an operon with two other genes, era and recO. The sequence of the recO gene beyond era indicated it could encode a protein of approximately 26 kilodaltons and, like rnc and era, had codon usage consistent with a low level of expression. Experiments using antibiotic cassettes to disrupt the genes rnc, era, and recO showed that era is essential for E. coli growth but that rnc and recO are dispensable.
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PMID:Genetic analysis of the rnc operon of Escherichia coli. 254 Jan 51

We have isolated on a multicopy plasmid a mutant rrnB ribosomal RNA operon containing a 130 base-pair deletion immediately preceding the 23 S rRNA gene. The deletion shortens by just three base-pairs the 26 base-pair complementarity of the sequences that flank the 23 S rRNA gene, and which normally form an RNase III cleavage site in the rrnB primary transcript. Both in vivo and in vitro, cleavage at the altered RNase III site was almost completely abolished by the mutation. Our results therefore indicate that even a small perturbation of the double-stranded region normally recognized by RNase III strongly inhibits the action of the enzyme.
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PMID:A mutation in an Escherichia coli ribosomal RNA operon that blocks the production of precursor 23 S ribosomal RNA by RNase III in vivo and in vitro. 258 39

RNase III has been implicated in the control of gene expression by the processing of mRNA. We have found that the rnc operon is autoregulated; rnc- mutant strains oversynthesize the operon's mRNA and protein products. A site in the 5'-noncoding region of the operon's message is cleaved by RNase III. This site-specific cleavage appears to be the initial step in the functional inactivation of the message, since the half-life of the cut message is dramatically shorter than that of the uncut message.
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PMID:Autoregulation of RNase III operon by mRNA processing. 258 4

Immediate precursors of 16S rRNA are processed by endonucleolytic cleavage at both 5' and 3' mature termini, with the concomitant release of precursor fragments which are further metabolized by both exo- and endonucleases. In wild-type cells rapid cleavages by RNase III in precursor-specific sequences precede the subsequent formation of the mature ends; mature termini can, however, be formed directly from pre-16S rRNA with no intermediate species. The direct maturation is most evident in a strain deficient in RNase III, and the results in whole cells are consistent with results from maturation reactions in vitro. Thus, maturation does not require cleavages within the double-stranded stems that enclose mature rRNA sequences in the pre-16S rRNA.
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PMID:Processing pathway of Escherichia coli 16S precursor rRNA. 264 97

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.
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PMID:RNA processing by RNase III is involved in the synthesis of Escherichia coli polynucleotide phosphorylase. 282 71

The location of the RNA start point of in vivo Q-activated late gene RNA of bacteriophage lambda has been determined to be identical to the start point of in vitro 6 S RNA. The 6 S RNA is made early in infection and is efficiently antiterminated by Q. Two RNase III cut sites are located within Q-dependent RNA sequences, 209 and 270 bp from the beginning of the late transcript, and lie on the stem of an inverted repeat which has features in common with previously described RNase III processing sites. This is the third example of RNase III cut sites immediately downstream of transcription termination points in lambda, the others being antiterminated N gene mRNA and int gene mRNA.
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PMID:Q-mediated late gene transcription of bacteriophage lambda: RNA start point and RNase III processing sites in vivo. 284 40

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.
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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.
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PMID:RNase III stimulates the translation of the cIII gene of bacteriophage lambda. 295 96


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