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

---

Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An abortive infection of a rabbit cornea cell line (RC-60) by vesicular stomatitis virus (VSV), yielding less than 1 PFU/cell, was converted to a productive infection, yielding 1,900 PFU/cell, when cells were superinfected with vaccinia. Studies on the synthesis of VSV-directed RNA in RC-60 cells suggest that the abortive infection by VSV alone may be due in part to (i) a limited production of 40S virion RNA and (ii) a markedly reduced activity of virion-bound transcriptase activity in RC-60 cells compared to the activity in mouse L cells, a permissive host for VSV. No recognizable VSV structures, except a small amount of viral core structures, were produced by the abortive infection. In contrast, double infection of RC-60 cells with VSV and vaccinia in the presence of hydroxyurea resulted in the production of infective B particles of VSV. Although the function supplied by vaccinia responsible for the productive replication of VSV in double infected RC-60 cells has not been identified, metabolic inhibitor studies indicate that continuous vaccinia-dependent RNA synthesis is required for maximal production of infective VSV. The possibility is considered that vaccinia may supply a product or function required for VSV replication which is ordinarily supplied by the host but which is lacking in RC-60 cells.
...
PMID:Abortive infection of a rabbit cornea cell line by vesicular stomatitis virus: conversion to productive infection by superinfection with vaccinia virus. 16 5

In this study, we have located the sites of transcription initiation and termination on a cloned fragment of ribosomal DNA from X. laevis, and have sequenced the surrounding nucleotides. As reported previously (Reeder, Sollner-Webb and Wahn, 1977), about 25% of the 40S rRNA precursor molecules isolated from oocytes have polyphosphate 5' termini and are therefore presumed to represent primary transcripts. These ends hybridize specifically to the 221 bp DNA fragment and removed the overhanging DNA region with S1 nuclease. In the other, we hybridized 40S RNA to a 221 bp fragment of ribosomal DNA. The nucleotides encoding the 5' end of the 40S RNA were located more precisely by two methods. In one, we hybridized 40S RNA to the 221 bp DNA fragment and removed the overhanging DNA region with S1 nuclease. In the other, we hybridized 40S RNA to a smaller DNA fragment and extended the recessed 3' terminus of the DNA using reverse transcriptase. The resultant DNA fragments were sized on sequencing gels. Both determinations map the 5' end of 40S RNA at the same site in the rDNA, about 2250 bp upstream from the Eco RI site in the 18S rRNA coding sequence. At this site we find a DNA sequence beginning AGGGGAAGAC.... which agrees with partial sequence data from the 5' end of polyphosphorylated and bulk 40S rRNA. Features of this region of the ribosomal DNA will be discussed in this paper. A 227 nucleotide region surrounding the initiation site was also sequenced from an independently derived clone and found to differ in only one nucleotide. In addition, a sequence is found about 1100 nucleotides upstream from the 5' end of the gene that has 90% homology to the sequence from nucleotides minus 125 to +4 in the initiation region. At the termination region, X. laevis ribosomal DNA has a single recognition site for the restriction enzyme Hind III in each repeating unit. Using the S1 nuclease technique, the 3' termini of both the 40S precursor and mature 28S rRNA are seen to map within this recognition sequence. The sequence surrounding the Hind III site has striking homology to termination sites recognized by other RNA polymerase classes. Sequences with similar features are also found upstream from the initiation site.
...
PMID:The nucleotide sequence of the initiation and termination sites for ribosomal RNA transcription in X. laevis. 49 80

HeLa cell nuclei, isolated 17 h after infection with human adenovirus type 2 (Ad2), were treated with 200 mM ammonium sulfate. The extract (S200 fraction) contained 50 to 70% of the nonintegrated Ad2 DNA, which was in the form of nucleoprotein complexes. These complexes contained native, intact Ad2 DNA (with the exception of replicative intermediates) and could be partially purified and resolved by velocity gradient centrifugation. Using high-salt (200 mM ammonium sulfate) incubation conditions, more than 95% of the nuclear RNA polymerase activity belonged to class B. About 45% of the class B enzyme molecules bound to DNA in the nuclei (those "engaged" in RNA synthesis) were released from the nuclei in the form of Ad2 transcriptional complexes by treatment with 200 mM ammonium sulfate. At least 90% of the RNA synthesized in high salt in the nuclei or in the S200 fraction was Ad2 specific, and essentially all of this RNA was complementary to the l strand of Ad2 DNA. These findings are compatible with what is known about Ad2-specific RNA synthesis in vivo. The analysis of the RNA synthesized from partially purified transcriptional complexes supports the contention that its transcription is almost entirely asymmetric, and that the asymmetry observed in vivo is not a consequence of the rapid degradation of h-strand transcripts. The RNA synthesized in vitro in the absence of detectable RNase activity sedimented with a maximum size of 35 to 40S. Less than 5% of the nuclear or the S200 fraction RNA polymerase activity was class C when assayed under non-reinitiating conditions. Although much of the RNA synthesized by the class C enzyme was Ad2 specific, 5.5S virus-associated RNA was not the predominant product. The isolation of Ad2 DNA transcriptional complexes provides an attractive system for further characterizing the Ad2 DNA template used for transcription and for studying the regulation of the expression of the Ad2 genome during the productive infection cycle.
...
PMID:Characterization of adenovirus type 2 transcriptional complexes isolated from infected HeLa cell nuclei. 95 Jun 90

In subcellular extracts of Kunjin virus-infected cells prepared by lysis and differential centrifugation, the viral RNA polymerase, RNA and proteins were associated mainly with cytoplasm. When the cytoplasmic extract (500 g supernate) of infected cells labelled for 3 h from 24 h post-infection was further fractionated by rapid centrifugation through a sucrose density gradient, all viral products were located only in dense or "heavy membrane" fractions, which contained three types of virus-induced morphologically distinct membrane structures. These dense fractions were treated with 0.5% NP40 and the soluble material was again centrifuged through a sucrose gradient for analyses as before. Viral RNA polymerase activity was retained and was associated with replicative intermediate RNA and some replicative form RNA in the peak enzyme fractions sedimenting at 20S to 40S. Enrichment of NS3 and of the small nonstructural proteins NS2A and NS2B/NS4A was apparent in these fractions which were well separated from the slow sedimenting structural proteins. No detergent-resistant structures in the "heavy membrane" fractions other than ribosome-like particles were visible. The data show that the RNA polymerase complex cosedimented with virus-induced membrane structures and remained associated with specific nonstructural proteins and replicative intermediate RNA after detergent treatment.
...
PMID:Molecular and ultrastructural analysis of heavy membrane fractions associated with the replication of Kunjin virus RNA. 132 51

The effect of Rev on cytoplasmic accumulation of the singly spliced human immunodeficiency virus type 1 (HIV-1) vif, vpr, and env/vpu RNAs was examined by using a quantitative RNA polymerase chain reaction (PCR) analysis following transfection of complete proviral molecular clones into lymphoid cells. Previously published studies using subgenomic env constructs in nonlymphoid cell types concluded that Rev was necessary for cytoplasmic accumulation of high levels of unspliced env RNA and that, by analogy, Rev must be necessary for the cytoplasmic accumulation of all HIV-1 RNAs that contain the Rev-responsive element (RRE). We confirm those results in COS cells. Unexpectedly, in lymphoid cells, we find that although Rev acts somewhat to increase the cytoplasmic level of full-length HIV-1 RNA, Rev has little or no effect on cytoplasmic accumulation of singly spliced HIV-1 RNAs. However, Env protein expression was greatly reduced in the absence of Rev. Analysis of the cytoplasmic RNA revealed that in the absence of Rev or the RRE, the cytoplasmic vif, vpr, and env/vpu 2 RNAs were not associated with polysomes but with a complex of 40S-80S in size. Consequently, efficient expression of the Vif, Vpr, Vpu, and Env proteins from these RNAs is dependent on Rev. These results exclude a mechanism whereby the sole function of Rev is simply to export RNAs from nucleus to cytoplasm. We discuss other models to take into account the dependence on Rev for efficient translation of cytoplasmic HIV-1 RNAs.
...
PMID:Rev is necessary for translation but not cytoplasmic accumulation of HIV-1 vif, vpr, and env/vpu 2 RNAs. 182 22

In order to define the RNA polymerase I transcriptional apparatus and how it might interact with regulatory signals, the DNA sequences necessary for 40S rRNA transcription in Neurospora crassa were determined. A systematic set of deletion, substitution and insertion mutations were assayed in a homologous in vitro system. The sequences required for transcription of the gene consist of two large domains (I and II) from -113 to -37, and -29 to +4, respectively. Complete deletion of either domain abolished transcription. Upstream sequences confer a small stimulation of transcription. Domain II includes a TATA sequence at -5 which is sensitive to a small (2 bp) substitution and which is conserved among the large rRNA genes of many organisms. Domain I includes a sequence, termed the 'Ribo box', which is also required for transcription of the Neurospora 5S rRNA genes (1), and which occurs in the 5' region of a Neurospora ribosomal protein gene. The 5S and 40S Ribo boxes are shown to be functionally interchangeable.
...
PMID:Two complex regions, including a TATA sequence, are required for transcription by RNA polymerase I in Neurospora crassa. 213 32

In the ribosomal genes of X. laevis, the sequence GACTTGCNC is found about 60bp upstream of the gene promoter (T3) and is necessary and sufficient to cause termination of RNA polymerase I transcription. At the 3' end of the 40S precursor coding region (T2) a sequence differing by one nucleotide, GACTTGCNG, directs RNA 3' end formation but allows polymerase to transcribe on into the intergenic spacer (Labhart and Reeder, 1989, Genes and Dev. 4: 269-276). Sites corresponding to T2 and T3 are also found in a related species, X. borealis. Inspection of the T2 sequence in X. borealis reveals that it contains two copies of the terminator sequence, GACTTGCNC, located 15 and 96 bp downstream of the 3' end of the 40S precursor coding region. Here we present functional tests of those two T2 elements that show that, as predicted from the sequence, they both show termination activity and are functionally indistinguishable from the T3 site in X. laevis. These results suggest that X. laevis T2 is an example of a naturally occurring point mutation, and the inability to terminate transcription at T2 is an exception to the general pattern of ribosomal gene transcription in higher eukaryotes.
...
PMID:Functional difference between the sites of ribosomal 40S precursor 3' end formation in Xenopus laevis and Xenopus borealis. 240 47

Translation of foreign mRNAs is enhanced by a cis-acting derivative (omega') of the 5'-leader sequence (omega) of tobacco mosaic virus RNA (vulgare strain). To explain this effect we have conducted several experiments in vitro. 1. The presence of various 5'-terminal sequences, including omega', did not significantly increase the half-lives of chloramphenicol acetyltransferase (CAT) or neomycin phosphotransferase (NPTII) mRNAs in wheat-germ extract. Also, a long leader sequence, unrelated to omega', did not enhance expression of NPTII mRNA in vitro. 2. The ability of several leader sequences, including omega', to form multiple initiation complexes with 80S (wheat germ) ribosomes was examined using CAT or NPTII mRNAs incubated in the presence of sparsomycin. Formation of disome complexes was unrelated to the capacity of a 5'-leader sequence to enhance translation. 3. Expression of CAT mRNA in both wheat germ extract and messenger-dependent rabbit reticulocyte lysate was less susceptible to inhibition by increasing salt concentration when a 5'-proximal omega' sequence was present. This effect was less marked when the CAT mRNA was capped. Conversely at high salt concentrations, capping was less stimulatory for mRNA with a 5'-proximal omega' sequence. These data suggest that omega' and the cap enhance translation, at least in part, by a similar mechanism. We propose that both features reduce RNA secondary structure, thereby rendering the 5' terminus more accessible to scanning by 40S ribosomal subunits and/or interaction with associated initiation factors. This conclusion was supported by computer-based secondary-structure analyses of our SP6 RNA polymerase transcript sequences. The ability of 5' leader sequences from brome mosaic virus RNA 3, alfalfa mosaic virus RNA 4, and the genomic RNAs of turnip yellow mosaic virus, Rous sarcoma virus or tobacco mosaic virus (tomato strain) to enhance mRNA translation in eukaryotic systems may also be correlated with their respective secondary structures. A different mechanism probably accounts for the omega'-dependent enhancement of mRNA expression in Escherichia coli or in E. coli cell-free systems.
...
PMID:Studies on the mechanism of translational enhancement by the 5'-leader sequence of tobacco mosaic virus RNA. 284 Nov 27

On the tandemly linked ribosomal genes of Xenopus laevis, the RNA polymerase transcribes past the 3' end of the 40S coding region and terminates at T3 just upstream of the gene promoter. The close proximity of T3 to the gene promoter, and the functional interdependence of these two elements, has led to the suggestion that polymerase terminating at T3 might be passed directly to the gene promoter. Such a mechanism might be necessary to maintain the characteristic high rate of transcription initiation seen on the ribosomal genes. We have performed a direct test of this model by introducing chain-terminating psoralen adducts into a circular plasmid containing a single gene promoter with its attendant T3 region upstream. We find that the psoralen adducts can completely prevent polymerase from traveling around the template circle (and thus prevent polymerase from approaching the promoter from upstream) without affecting the rate of transcription initiation at the gene promoter. This result suggests that recycling of polymerase from T3 to the promoter is not a significant mechanism in maintaining high initiation rates.
...
PMID:A test of 'polymerase handover' as a mechanism for stimulating initiation by RNA polymerase I. 291 70

cDNA clones encoding three antigenically related human ribosomal phosphoproteins (P-proteins) P0, P1, and P2 were isolated and sequenced. P1 and P2 are analogous to Escherichia coli ribosomal protein L7/L12, and P0 is likely to be an analog of L10. The three proteins have a nearly identical carboxy-terminal 17-amino-acid sequence (KEESEESD(D/E)DMGFGLFD-COOH) that is the basis of their immunological cross-reactivity. The identities of the P1 and P2 cDNAs were confirmed by the strong similarities of their encoded amino acid sequences to published primary structures of the homologous rat, brine shrimp, and Saccharomyces cerevisiae proteins. The P0 cDNA was initially identified by translation of hybrid-selected mRNA and immunoprecipitation of the products. To demonstrate that the coding sequences are full length, the P0, P1, and P2 cDNAs were transcribed in vitro by bacteriophage T7 RNA polymerase and the resulting mRNAs were translated in vitro. The synthetic P0, P1, and P2 proteins were serologically and electrophoretically identical to P-proteins extracted from HeLa cells. These synthetic P-proteins were incorporated into 60S but not 40S ribosomes and also assembled into a complex similar to that described for E. coli L7/L12 and L10.
...
PMID:Human acidic ribosomal phosphoproteins P0, P1, and P2: analysis of cDNA clones, in vitro synthesis, and assembly. 332 86


1 2 3 4 5 Next >>

---