Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A precursor molecule for 10Sb (M1) RNA, the RNA moiety of the RNA processing enzyme ribonuclease P (EC 3.1.26.5), is accumulated transiently in an Escherichia coli strain containing a plasmid that carries the 10Sb RNA gene. The same RNA precursor molecule is accumulated, in relatively large quantities, in a temperature-sensitive RNase E- mutant at the nonpermissive temperature. The RNA precursor includes 10Sb RNA and an extra 3' fragment that contains a termination stem and loop. It can be processed in vitro to a molecule the size of 10Sb RNA. None of the four endoribonucleases of E. coli--RNase III, RNase E, RNase F, or RNase P--takes part in this cleavage reaction. Therefore, we suggest that the processing of the precursor-10Sb RNA to 10Sb RNA is carried out by a thus-far unidentified endoribonuclease. The accumulation of a RNA molecule in a RNase E- mutant that does not contain a cleavage site for RNase E has been encountered previously and can be explained by assuming the existence of a RNA processing complex in the E. coli cell.
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PMID:Identification of a precursor molecular for the RNA moiety of the processing enzyme RNase P. 619 33

Using RNA-directed synthesis of the alpha-peptide of beta-galactosidase as an assay, a factor was purified that inactivated further function of the mRNA. In the presence of Ca2+ ions to inhibit most nuclease activity, inactivation of mRNA occurred during incubation with ribosomes or with a 1 M KCl wash of ribosomes. The inactivation activity required Mg2+ ions, and purified as a single factor which did not bind to DEAE-cellulose, but bound reversibly to phosphocellulose. The factor eluted from Sephadex G-150 with an apparent molecular weight of about 43,000. Purified 700-fold, it showed no detectable exonuclease activity, and little or no cleavage of a variety of single-stranded substrates, including full length lac operon mRNA; but repurified inactivated mRNA was still inactive for protein synthesis. The factor did not inhibit poly(U)-directed polyphenylalanine synthesis. When proteins isolated from the ribosomal wash were individually tested, highly purified RNase III, which purifies in the same way and has the same size, also inactivated lac mRNA. The ribosomal wash from an RNase III- strain showed little if any activity compared to that from an isogenic RNase III+ strain. The possibility of a site-specific inactivating cleavage of mRNA by RNase III at or near the 5' end is considered.
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PMID:Functional inactivation of lac alpha-peptide mRNA by a factor that purifies that Escherichia coli RNase III. 625 91

9-S RNA is a processing intermediate that accumulates in an RNase E- strain of Escherichia coli. It spans from the RNase III cleavage site, after 23-S rRNA, to the 3' end of the transcript and is derived from rRNA genes which do not contain tRNAs distal to 5-S rRNA. Here, we have studied the processing of 9-S RNA with ribonuclease E. RNase E cleaves 9-S RNA in two sites: one of these is three nucleotides upstream from the 5' end of 5-S rRNA, the other downstream from its 3' end. Both cleavages are probably introduced by the same enzyme, since both cleavages are thermolabile when an extract of a temperature-sensitive RNase E mutant was used for processing in vitro. In order to asses the role of 5' and 3' end precursor-specific sequences in the RNase E reaction, we isolated the molecules lacking nucleotides at the 5' or 3' end. Molecules having the 5' end of 9-S RNA but missing nucleotides from the 3' end (called 8-S RNA) were as good a substrate for RNase E as 9-S, RNA itself. However, molecules having the 3' end of 9-S RNA but the 5' end of p5 (called 7-S RNA), were less efficient substrates for RNase E. Finally, the removal of as little as seven nucleotides from the 5' end of 8-S RNA rendered it almost completely unsuitable as a substrate for RNase E.
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PMID:Maturation of 5-S rRNA: ribonuclease E cleavages and their dependence on precursor sequences. 633 34

A double-stranded ribonuclease has been purified more than 90-fold to near homogeneity from the yeast, Saccharomyces cerevisiae. The enzyme shows a high specificity for double-stranded RNA as its substrate. It has a molecular weight of 27000 as determined by sodium dodecyl sulphate/polyacrylamide gel electrophoresis. The enzyme degrades dsRNA optimally at 30 degrees C; it is stimulated by KCl and by the -SH reagent, dithiothreitol. In contrast to RNase III from Escherichia coli, the yeast enzyme is inhibited by divalent cations. Physiological studies have demonstrated that in vivo levels of the enzyme activity fell during the latter part of the exponential growth phase but rose during stationary phase. The specific activity of the enzyme in nitrogen-starved yeast cells was 2-3-fold higher than in non-starved cells. The enzyme could be detected in yeast strains containing both, one or none of the species of cytoplasmic dsRNA (L and MdsRNAs) and may, therefore, have some wider role.
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PMID:Purification and properties of a double-stranded ribonuclease from the yeast Saccharomyces cerevisiae. 636 60

RNase III makes the initial cleavages that excise Escherichia coli precursor 16S and 23S rRNA from a single large primary transcript. In mutants deficient in RNase III, no species cleaved by RNase III are detected and the processing of 23S rRNA precursors to form mature 23S rRNA fails entirely. Instead, 50S ribosomes are formed with rRNAs up to several hundred nucleotides longer than mature 23S rRNA. Unexpectedly, these aberrant subunits function well enough to participate in protein synthesis and permit cell growth. Consistent with the inference that RNase III cleavages are absolutely required for 23S rRNA maturation, when 50S ribosomes from a strain deficient in RNase III were incubated with a ribosome-free extract from a RNase III+ strain, rRNA species processed by RNase III and species with normal mature 23S rRNA termini were produced.
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PMID:RNase III cleavage is obligate for maturation but not for function of Escherichia coli pre-23S rRNA. 636 33

The Escherichia coli rpsO gene gives rise to different mRNA species resulting either from termination of transcription or from processing of primary transcripts by RNase E and RNase III. The main degradation pathway of these transcripts involves a rate-limiting RNase E cleavage downstream of the structural gene which removes the 3' terminal stem-loop structure of the transcription terminator. This structure protects the message from the attack of 3'-5' exonucleases and its removal results in very rapid degradation of the transcript by polynucleotide phosphorylase and RNase II. Polynucleotide phosphorylase is also able to degrade slowly the mRNA harboring the 3' terminal hairpin of the terminator. In contrast, RNase II appears to protect the rpsO mRNA species which retains the 3' hairpin structure. Rapid degradation of the rpsO mRNA is observed after inactivation of RNase II even in a strain deficient for RNase E and polynucleotide phosphorylase. The enzyme(s) involved in this degradation pathway is not known. We detected an unstable elongated rpsO mRNA presumably resulting from the addition of nucleotides at the 3' end of the transcript.
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PMID:Roles of RNase E, RNase II and PNPase in the degradation of the rpsO transcripts of Escherichia coli: stabilizing function of RNase II and evidence for efficient degradation in an ams pnp rnb mutant. 751 47

RNase protection experiments show that the sizes of the two R100 finP molecules are 74 and 135 nucleotides. In an RNase III mutant, finP transcripts form stable double-stranded hybrids of 108 bp and 68 bp with traJ transcripts. RNase protection experiments also show that most R100-1 transcripts originating in traM cross the traM-traJ intergenic region and end inside the untranslated leader region of traJ. Some extend into the traJ open reading frame. These findings mean that the antisense finP RNA, thought to regulate traJ translation, must regulate traJ transcripts from both J and M promoters.
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PMID:traJ sense RNA initiates at two different promoters in R100-1 and forms two stable hybrids with antisense finP RNA. 752 20

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.
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PMID:Rescue of the fission yeast snRNA synthesis mutant snm1 by overexpression of the double-strand-specific Pac1 ribonuclease. 761 61

Ribonuclease II (RNase II), encoded by the rnb gene, is one of the two major Escherichia coli exonucleases involved in mRNA degradation. Some of the ribonucleases implicated in this process have recently been shown to be inter-regulated. In this paper we studied the effects of the endonucleases RNase E and RNase III in rnb expression. We have shown that RNase E cleaves the rnb message internally: when this ribonuclease is inactivated rnb mRNA accumulates with a concomitant increase in RNase II activity. RNase III also affects RNase II expression but in an indirect way. We discuss these implications for the regulation of mRNA degradation.
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PMID:The role of endonucleases in the expression of ribonuclease II in Escherichia coli. 764 46

RNases H are traditionally thought to degrade RNA only in RNA-DNA hybrid form. We found that the wild-type Moloney murine leukemia virus (M-MuLV) reverse transcriptase (RT) was capable of degrading RNA in RNA-RNA duplexes as well as in RNA-DNA hybrids, as assayed by in situ gel techniques. Escherichia coli RNase H does not degrade the RNA-RNA duplex in this assay, while E. coli RNase III, a double-strand-specific ribonuclease, does. The apparent specific activity of M-MuLV RT on RNA-RNA duplexes is similar to that on RNA-DNA hybrids. Neither the DNA polymerase domain nor the RNase H domain of RT expressed individually exhibited this RNA-RNA activity. We have generated a series of mutations in the RNase H domain of M-MuLV RT, expressed the mutant enzymes in E. coli, and assayed these mutants for various activities. All RTs were as active as the wild type in the oligo(dT):poly(rA) DNA polymerase assay, and many retained both nuclease activities. Two enzymes with mutations at the carboxyl terminus of the RNase H domain retained RNA-DNA activity, but not RNA-RNA activity. Another mutant enzyme showed the opposite phenotype, retaining RNA-RNA, but not RNA-DNA, nuclease activity. Thus, we were able to genetically separate the two activities. These results may be helpful in defining enzyme-substrate interactions.
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PMID:Nuclease activities of Moloney murine leukemia virus reverse transcriptase. Mutants with altered substrate specificities. 769 92


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