Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The 76 bp sequence found in the upstream region of a gene for 26S rRNA (rrn26) is duplicated in the upstream region of a gene for initiator methionine tRNA (trnfM) in the mitochondrial genome of rice. An in vitro capping/ribonuclease protection assay and primer extension analysis demonstrated that the transcription of trnfM and of rrn26, which are at least 190 kb from one another in the rice mitochondrial genome, starts from these same sequences in the upstream regions of the respective genes. This result indicates that the short sequence that is duplicated in the upstream regions of trnfM and rrn26 in rice mtDNA is recognized as the promoter of each respective gene.
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PMID:A small repeated sequence contains the transcription initiation sites for both trnfM and rrn26 in rice mitochondria. 759 19

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

Human eosinophil-derived neurotoxin (EDN) and eosinophil cationic protein (ECP) are members of a unique subfamily of rapidly evolving primate ribonuclease genes that emerged via a gene duplication event occurring after the divergence of Old World from New World monkeys (Rosenberg, H. F., Dyer, K. D., Tiffany, H. L., and Gonzalez, M. (1995) Nature Genet. 10, 219-223). In this work, we studied the activity of the protein encoded by the EDN/ECP homolog of the New World monkey, Saguinus oedipus (marmoset), a representative of the "ancestral" single sequences. Although the nucleotide sequence of the single marmoset gene (mEDN) was equally homologous (82%) to both human genes, the encoded amino acid sequence, calculated isoelectric point, and immunoreactivity all suggested a closer relationship with EDN. Furthermore, mEDN (at 0.3-1.0 microM concentrations) had no measurable anti-staphylococcal activity, suggesting functional as well as structural similarity to EDN. However, with yeast tRNA as substrate, mEDN had significantly less ribonuclease activity than EDN; Michaelis constants were nearly identical (Km (mEDN) = 0.67 microM; Km (EDN) = 0.70 microM), while turnover numbers differed by a factor of 100 (kcat (mEDN) = 0.91 s-1; kcat (EDN) = 0.64 x 10(-2) s-1). Thus, evolutionary constraints appear to have promoted two novel functions: increased cationicity/toxicity (ECP) and enhanced ribonuclease activity (EDN). The latter result is particularly intriguing, as it suggests a crucial role for ribonuclease activity in the (as yet to be determined) physiologic function of EDN.
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PMID:Eosinophil cationic protein and eosinophil-derived neurotoxin. Evolution of novel function in a primate ribonuclease gene family. 853 Apr 35

We have purified a high molecular weight ribonuclease (hmRNase) from human milk by a two-step column chromatographic procedure and characterized the enzyme. The molecular mass of hmRNase is 80 kDa as determined from SDS-polyacrylamide gel electrophoresis. The pH optimum of the enzyme is in the range of 7.5-8.0, similar to other secretory RNases. hmRNase is pyrimidine-specific and cleaves the phosphodiester bond 3' to a pyrimidine residue. It selectively degrades the pyrimidine strand in poly(rA):poly(rU) and poly(dA):poly(rU) double stranded substrates. The extent of degradation for naturally occurring RNAs vary in the order tRNA < rRNA < mRNA at low enzyme concentrations. hmRNase shows allosteric behavior with positive cooperativity in its reaction on polynucleotide substrates. The activity of the enzyme is enhanced in the presence of monoribonucleotides. Antiserum obtained against purified hmRNase did not cross-react with low molecular weight RNase which is also present in milk. In addition, an immunologically cross-reacting species could not be detected in the serum, suggesting the origin of hmRNase in the mammary gland but not blood.
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PMID:Purification and characterization of a high molecular weight ribonuclease from human milk. 768 36

A sequence-selective artificial ribonuclease was prepared by attaching ethylenediamine to the 5'-end of a DNA oligomer as the sequence-recognizing moiety. The hybrid, incorporating a 19-mer DNA which is complementary with the A44-A62 sequence of tRNA(Phe), hydrolyzed the tRNA selectively at the 3'-side of C63.
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PMID:Selective hydrolysis of tRNA by ethylenediamine bound to a DNA oligomer. 788 43

The polycistronic mRNA of the histidine operon is subject to a processing event that generates a rather stable transcript encompassing the five distal cistrons. The molecular mechanisms by which such a transcript is produced were investigated in Escherichia coli strains carrying mutations in several genes for exo- and endonucleases. The experimental approach made use of S1 nuclease protection assays on in vivo synthesized transcripts, site-directed mutagenesis and construction of chimeric plasmids, dissection of the processing reaction by RNA mobility retardation experiments, and in vitro RNA degradation assays with cellular extracts. We have found that processing requires (1) a functional endonuclease E; (2) target site(s) for this activity in the RNA region upstream of the 5' end of the processed transcript that can be substituted by another well-characterized rne-dependent cleavage site; (3) efficient translation initiation of the first cistron immediately downstream of the 5' end; and (4) a functional endonuclease P that seems to act on the processing products generated by ribonuclease E. This is the first evidence that ribonuclease P, an essential ribozyme required for the biosynthesis of tRNA, may also be involved in the segmental stabilization of a mRNA.
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PMID:Ribonuclease E provides substrates for ribonuclease P-dependent processing of a polycistronic mRNA. 800 21

A recombination event at the 3' end of RNA 3 in a pseudorecombinant virus (C1C2T3) having RNAs 1 and 2 from TrK7-cucumber mosaic virus (CMV) and RNA 3 from P-tomato aspermy virus (TAV) was detected by ribonuclease protection assay (RPA). Sequence analysis of the 3' end of RNA 3 of C1C2T3 and of its parental CMV and TAV strains showed that RNA 3 of C1C2T3 had a hybrid nature in which most of the 3' noncoding region (3' ncr), including the whole 3' terminal tRNA-like structure, was derived from CMV RNA 2 by recombination. Recombination may have occurred in two steps. The first one would have caused the duplication of a large region 5' to the 3' end tRNA-like structure, derived from TAV and from CMV. The second one would have eliminated the TAV-derived sequences in this duplicated region. Competition experiments in tobacco plants showed that in a context of RNA 1 + 2 from CMV, RNA 3 from TAV is outcompleted by RNA 3 of CMV, but the recombinant TAV RNA 3 with the 3' end of CMV outcompetes both TAV and CMV RNA 3. This shows an increase in relative fitness associated with the recombinant nature of RNA 3. Our results document the potential importance of RNA-RNA recombination in the determination of the genetic structure of RNA viral populations.
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PMID:Increase in the relative fitness of a plant virus RNA associated with its recombinant nature. 805 60

Using an in vitro ribonuclease protection assay, it was shown that synthetic antisense transcripts from the 5'-upstream region of the beta-tubulin gene are efficiently imported into isolated Leishmania mitochondria. Import occurred after a lag of about 30 min at 25 degrees C and was dependent on ATP. Preincubation experiments suggested that import consists of a slow interaction of mitochondria with RNA, followed by rapid ATP-dependent uptake. Import was saturable with antisense RNA at about 1 nM concentration, and sequence-specific, as shown by lack of import of other labelled transcripts. Deletion analysis demonstrated a correlation between efficiency of import and the number of oligopurine motifs on the antisense RNA. Several small ribosomal RNAs (srRNAs) and Leishmania tRNA competed with antisense RNA for import. Incubation of mitochondria with srRNAs and tRNA in the presence of radiolabelled UTP resulted in the ribonuclease-resistant labelling of these RNAs by the mitochondrial terminal uridylyl transferase. Extracts of isolated mitochondria contain a factor binding to antisense RNA, as shown by gel retardation assay. These observations indicate the presence of a receptor-mediated import pathway for srRNAs and tRNA in Leishmania mitochondria.
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PMID:Import of small RNAs into Leishmania mitochondria in vitro. 807 74

The prr locus was originally described as coding a ribonuclease that is activated after phage T4 infection to cut within the anticodon of a specific tRNA, inactivating protein synthesis and thus blocking phage development. Wild-type T4 phage has two genes coding the enzymes polynucleotide kinase and RNA ligase, whose only function seems to be to repair the damage done by the anticodon nuclease. As the only apparent function of the prr ribonuclease is to combat phage infection, it can be considered as an RNA-based restriction enzyme. In non-infected cells, the prr enzyme is kept inactive in a complex with three other proteins which were predicted on the basis of DNA homologies to be the subunits of a type IC DNA restriction and modification system. Unlike other type IC systems so far characterized, prr is chromosomally rather than plasmid coded. However, sequences upstream from prr also have homology with sequences from the plasmid R124 and the prophage P1. We have now investigated the prr system and shown that it is indeed a bona fide type IC system which we call EcoprrI, and which is active both in vivo and in vitro. The system is fully functional even in the absence of the anticodon nuclease and seems to be a typical type I enzyme. EcoprrI recognizes the sequence CCA(N7)RTGC. One peculiarity is that, with low efficiency, EcoprrI will recognize and methylate variants of its recognition sequence such as CCT(N7)ATGC, which is methylated in one strand of the DNA only.
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PMID:The Escherichia coli prr region encodes a functional type IC DNA restriction system closely integrated with an anticodon nuclease gene. 814 41

Structural differences between native (modified) and in vitro transcribed (unmodified) Escherichia coli tRNA(Val) were explored by comparing their temperature-absorbance profiles as a function of magnesium ion concentration and by probing their solution conformation with single- and double-strand-specific endonucleases. In vitro transcribed tRNA(Val) has a less ordered structure as monitored by thermal melting profiles; its Tm is appreciably lower than that of native tRNA(Val) at all Mg2+ concentrations. Structure probing experiments with nuclease S1 and ribonuclease V1 show that the unmodified tRNA(Val) transcript is more susceptible to nuclease attack at low Mg2+ concentrations, particularly in the D- and T-loops, indicative of at least a partial disruption of D-loop/T-loop interactions. These experiments also provide evidence for temperature-dependent alternative conformations of the anticodon loop of native tRNA(Val). Modified nucleosides are essential for the stability of these conformers; they cannot be detected in the unmodified in vitro transcript. The observations suggest that post-transcriptional modifications in tRNA allow the adoption of unique conformations and act to stabilize those that are biologically active.
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PMID:Probing structural differences between native and in vitro transcribed Escherichia coli valine transfer RNA: evidence for stable base modification-dependent conformers. 817 44


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