Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.5 (RNase)
 17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A clone containing the Escherichia coli rna gene encoding the nonspecific endoribonuclease, RNase I, was isolated and sequenced. The sequence of the 1070-nucleotide (nt) fragment agreed completely with that of a rna clone recently reported by Meador and Kennell [Gene 95 (1990) 1-7]. The transcription start point (tsp) of rna was identified using primer extension analysis, and its promoter sequence was established by comparison of RNase I expression levels in various deletion mutants. Our results indicate that the rna promoter is highly unusual. Its -35 region shows a poor match to the consensus sequence, and moreover, it is located within a stem-loop structure that apparently is a Rho-independent transcription termination site for an upstream gene.
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PMID:The Escherichia coli rna gene encoding RNase I: sequence and unusual promoter structure. 139 76

Dissociation of RNA and DNA from Escherichia coli RNA polymerase in transcription complexes prepared with enzyme molecules located within and near a rho-dependent transcription termination region on bacteriophage T7 D111 DNA has been studied using a membrane filter-binding assay. Rho protein with ATP present mediated rapid (half-time approximately 27 s) simultaneous dissociation of about 50% of both RNA and DNA. RNA molecules were preferentially released from enzyme molecules located within the termination region. Rapid release of RNA and DNA depended on a nucleoside triphosphate but did not depend on sigma factor. Pretreatment of complexes with ribonuclease prevented dissociation of DNA. Nearly simultaneous dissociation of both RNA and DNA was also detected after a lag of 3 min when the isolated transcription complexes were incubated with all four ribonucleoside triphosphates in the absence of rho factor. In this case, release presumably occurred at the rho-independent termination site that is 5990 nucleotides downstream from the A1 promoter. Thus, the dissociation of DNA from RNA polymerase at rho-dependent and rho-independent transcription termination sites is coupled with or occurs spontaneously soon after the release of transcripts at both sites.
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PMID:Transcription termination factor rho mediates simultaneous release of RNA transcripts and DNA template from complexes with Escherichia coli RNA polymerase. 388 62

Mutants in Escherichia coli transcription termination factor Rho, termed rho(nusD), were previously isolated based on their ability to block the growth of bacteriophage T4. Here we show that rho(nusD) strains have decreased average half-lives for bulk cellular mRNA. Decreased E. coli message lifetimes could be because of increased ribonuclease activity in the rho mutant cells: if a Rho-dependent terminator precedes a ribonuclease gene, weaker termination in the rho mutants could lead to nuclease overexpression. However, inactivation of ribonuclease genes in rho026 cells did not relieve the defective phage growth. Unexpectedly, expression of the pBR322 Rop protein, a structure-specific, sequence-independent RNA-binding protein, in rho(nusD) cells restored the ability of T4 to grow and prolonged cellular message half-life in both the wild-type and the rho026 mutant. These results suggest that it is the RNA-binding ability of Rho rather than its transcription termination function that is important for the inhibition of bacteriophage growth and the shorter bulk mRNA lifetime. We propose that altered interaction of the mutant Rho with mRNA could make the RNA more susceptible to degradation. The inability of the RNA-binding proteins SrmB and DeaD to reverse the rho mutant phenotype when each is overexpressed implies that the required RNA interactions are specific. The results show novel roles for Rho and Rop in mRNA stability.
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PMID:Effects on mRNA degradation by Escherichia coli transcription termination factor Rho and pBR322 copy number control protein Rop. 917 54

In order to investigate the involvement of Ras and/or Rho proteins in the induction of the inducible isoform of nitric oxide synthase (NOS II) we used HMG-CoA reductase inhibitors (statins) and Clostridium difficile toxin B (TcdB) as pharmacological tools. Statins indirectly inhibit small G proteins by preventing their essential farnesylation (Ras) and/or geranylgeranylation (Rho). In contrast, TcdB is a glucosyltransferase and inactivates Rho-proteins directly. Human A549/8- and DLD-1 cells as well as murine 3T3 fibroblasts were preincubated for 18 h with statins (1 - 100 microM) or TcdB (0.01-10 ng ml(-1)). Then NOS II expression was induced by cytokines. NOS II mRNA was measured after 4 - 8 h by RNase protection assay, and NO production were measured by the Griess assay after 24 h. Statins and TcdB markedly increased cytokine-induced NOS II mRNA expression and NO production. Statin-mediated enhancement of NOS II mRNA expression was reversed almost completely by cotreatment with mevalonate or geranylgeranylpyrophosphate. It was only slightly reduced by farnesylpyrophosphate. Therefore, small G proteins of the Rho family are likely to be involved in NOS II induction. In A549/8 cells stably transfected with a luciferase reporter gene under the control of a 16 kb fragment of the human NOS II promoter (pNOS2(16)Luc), statins produced only a small increase in cytokine-induced NOS II promoter activity. In contrast, statins had a considerable superinducing effect in DLD-1 cells stably transfected with pNOS2(16)Luc. In conclusion, our studies provide evidence that statins and TcdB potentiate cytokine-induced NOS II expression via inhibition of small G proteins of the Rho family. This in turn results in an enhanced NOS II promoter activity and/or a prolonged NOS II mRNA stability.
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PMID:Inhibition of small G proteins of the rho family by statins or clostridium difficile toxin B enhances cytokine-mediated induction of NO synthase II. 1101 7

Mutations conferring resistance to the antibiotic rifampicin (Rif(r)) occur at specific sites within the ss subunit of the prokaryotic RNA polymerase. Rif(r) mutants of Escherichia coli are frequently altered in the elongation and termination of transcription. Rif(r) rpoB mutations were isolated in Bacillus subtilis and their effects on transcription elongation factor NusG and Rho-dependent termination were investigated. RNase protection assay, Northern analysis and the expression of nusG-lacZ fusions in cells with an inducible NusG suggested the B. subtilis nusG gene was autoregulated at the level of transcription. Rif(r) mutations that changed residue Q469 to a basic residue (Q469K and Q469R) enhanced autoregulation of nusG. A mutant expressing a truncated form of NusG, due to a nonsense mutation within the nusG gene, was isolated on the basis of the loss of autoregulation. The mechanism of autoregulation was found to be independent both of transcription termination factor Rho and of the promoter transcribing nusG. Autoregulation required sequences within the 5' coding sequence of the nusG gene or immediately upstream. This is the first evidence from any bacterium that Rif(r) RNA polymerases can display altered transcription regulation by NusG.
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PMID:Mutations in the ss subunit of the Bacillus subtilis RNA polymerase that confer both rifampicin resistance and hypersensitivity to NusG. 1110 62

The Rho family of small GTP-binding proteins are important signaling molecules that regulate the dynamics of the actin cytoskeleton and mediate changes in cell morphology and motility. Here, we describe the temporal and spatial patterns of expression of the Rho family member, rac, during the development of the amphibian, Xenopus laevis. We also present the deduced amino acid sequence of Xenopus rac (Xrac). At the amino acid level, Xrac is highly conserved relative to previously characterized rac homologs, and is nearly identical to human rac1. RNase protection assays and Western blot analysis indicate that Xrac mRNA and protein are present from fertilization through tailbud stages of development. Whole-mount in situ hybridizations show that Xrac transcripts are especially abundant in cells of the involuting marginal zone, and later, in the cranial neural crest, the developing central nervous system, and in the somites. The remarkable degree of evolutionary conservation observed in the Xrac primary structure together with its high level of expression in cells and structures critical to morphogenesis suggest a functionally important role for this Rho family member in early vertebrate development.
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PMID:cDNA cloning, sequence comparison, and developmental expression of Xenopus rac1. 1204 73

Here we report a unique processing pathway in Escherichia coli for tRNA(Leu5) in which the exoribonuclease polynucleotide phosphorylase (PNPase) removes the Rho-independent transcription terminator from the leuX transcript without requiring the RhlB RNA helicase. Our data demonstrate for the first time that PNPase can efficiently degrade an RNA substrate containing secondary structures in vivo. Furthermore, RNase P, an endoribonuclease that normally generates the mature 5'-ends of tRNAs, removes the leuX terminator inefficiently independent of PNPase activity. RNase P cleaves 4-7 nt downstream of the CCA determinant generating a substrate for RNase II, which removes an additional 3-4 nt. Subsequently, RNase T completes the 3' maturation process by removing the remaining 1-3 nt downstream of the CCA determinant. RNase E, G and Z are not involved in terminator removal. These results provide further evidence that the E. coli tRNA processing machinery is far more diverse than previously envisioned.
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PMID:Processing of the Escherichia coli leuX tRNA transcript, encoding tRNA(Leu5), requires either the 3'-->5' exoribonuclease polynucleotide phosphorylase or RNase P to remove the Rho-independent transcription terminator. 1990 95

In the conventional model of the Rho-dependent transcription termination, the terminator Rho binds to the rut (Rho utilization) site and translocates along the nascent RNA prior to making possible interactions with the elongating RNA polymerase (RNAP). Even though the interaction between Rho and isolated RNAs was studied in great detail, the same has never been shown with the nascent RNA emerging from the transcription elongation complex (EC). Direct demonstration and requirement of the Rho-nascent RNA binding become even more important because of the recently proposed alternative model where Rho loads onto the RNAP prior to the formation of the nascent RNA. Here, we have measured the direct association of Rho in vitro with the free RNAP, RNAP-promoter binary complex and stalled ECs with varied length of RNA. We observed the association of Rho only with the ECs having the rut-site-containing long nascent RNA. This association was significantly reduced when either a Rho mutant, Y80C, defective for RNA binding or an antisense oligo to the rut site was used or when the rut site was eliminated by RNase digestion or replacement with a random RNA sequence. The presence of EC-bound NusG, the binding partner of Rho, did not facilitate this association. RNase footprinting of the Rho-EC complex revealed a clear Rho-mediated protection of the rut sites on the nascent RNA. We concluded that the nascent RNA loading of Rho and its interaction with the rut site are mandatory and prerequisites for its recruitment to the EC under in vitro experimental conditions.
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PMID:Interaction with the nascent RNA is a prerequisite for the recruitment of Rho to the transcription elongation complex in vitro. 2192 Mar 69

The C3 toxin produced by Clostridium botulinum (C3bot) catalyzes the mono-ADP-ribosylation of the small GTPases Rho A, B and C, resulting in their inactivation. Recently, a specific endocytotic uptake mechanism of C3bot was identified in macrophages and myeloid leukemia cells. Here, we present a novel delivery system based upon a mutant C3bot devoid of ADP-ribosylation activity (C3Mut) and wild-type streptavidin (Stv). The C3Mut moiety mediates endocytosis into macrophages, whereas Stv functions as an adaptor protein for attaching biotinylated molecules to facilitate their subsequent internalization. First, a bioconjugate consisting of recombinant C3Mut and Stv was generated via a thioether linkage that tightly interacted with biotinylated bovine serum albumin as demonstrated by dot blot analysis. We then showed the internalization of C3Mut-Stv into J774A.1 macrophages by confocal microscopy and observed translocation into the cytosol using cell fractionation. The C3Mut-Stv bioconjugate did not affect cell viability. Next, we prepared mono-biotinylated RNase A, which was attached to the C3Mut-Stv transporter, and demonstrated its C3Mut-Stv-mediated delivery into the cytosol of J774A.1 cells. Finally, C3Mut-Stv also promoted the efficient uptake of mono-biotinylated lysozyme into J774A.1 cells, highlighting its versatility. This study intriguingly demonstrates the use of the novel C3Mut-Stv delivery system for protein transduction and may provide a basis for future applications, in particular, of cytotoxic RNase A mutants.
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PMID:Streptavidin-conjugated C3 protein mediates the delivery of mono-biotinylated RNAse A into macrophages. 2268 11

Controlled RNA degradation is known to be achieved via the exosome in Eukarya and Archaea, and the RNA degradosome in Bacteria. In this issue of the Biochemical Journal, Taghbalout et al. demonstrate in Escherichia coli that many additional proteins of the RNA degradation and processing network co-localize with the RNA degradosome in supramolecular structures. The latter appear as extended cytoplasmic membrane-associated assemblies that coil around the periphery of the cell when visualized by immunofluorescence microscopy. The co-localizing ensemble of RNA metabolic proteins includes RNaseE, PNPase (polynucleotide phosphorylase), the DEAD-box RNA helicase RhlB, the oligo-RNase Orn, RNases II and III, PAP I [poly(A) polymerase I], RppH (RNA pyrophosphohydrolase), proteins RraA and RraB that are negative regulators of RNaseE, and the RNA chaperone Hfq. Not all cellular RNA-binding proteins associate with these structures, as shown for EF-Tu (elongation factor Tu) and Rho helicase. Formation of the supramolecular architecture was shown to not be dependent on two other known cytoskeletal systems or on RNA de novo synthesis or nucleoid positioning within the cell. This novel dimension of compartmentalization in bacteria that lack classic cell compartments opens new perspectives on how RNA homoeostasis is achieved, organized and regulated in bacteria such as E. coli.
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PMID:Supramolecular membrane-associated assemblies of RNA metabolic proteins in Escherichia coli. 2426 91


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