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

The structural and enzymatic components of retroviral cores are formed by proteolytic cleavage of precursor polypeptides, mediated by the viral protease (PR). We constructed an active-site mutation, D37I, in the PR of avian leukosis virus. The D37I mutation was introduced into an infectious DNA clone, and quail cell lines expressing the mutant virus were established. These cell lines produce normal amounts of virus particles, the major internal protein components of which are the uncleaved gag and gag-pol precursors. As in other retroviral systems, the protease-defective virions are noninfectious and retain the "immature" type A morphology as determined by thin-section transmission electron microscopy. The virion cores are stable at nonionic detergent concentrations that completely disrupt wild-type cores. Digestion of mutant virions with exogenous PR in the presence of detergent leads to complete and correct cleavage of the gag precursor but incomplete cleavage of the gag-pol precursor. The protease-defective virions encapsidate normal amounts of genomic RNA and tRNA(Trp) that is properly annealed to the primer-binding site, but some of the genomic RNA remains monomeric. Results from UV cross-linking experiments show that the gag polyprotein of mutant virions interacts with viral RNA and that this interaction occurs through the nucleocapsid (NC) domain. However, within mutant virions the interaction of the NC domain with RNA differs from that of mature NC with RNA in wild-type virions. Reverse transcriptase (RT) activity associated with mutant virions is diminished but still detectable. Digestion of the virions with PR leads to a fivefold increase in activity, but this PR-mediated activation of RT is incomplete. Since in vitro cleavage of the gag-pol precursor is also incomplete, we hypothesize that amino acid sequences N terminal to the reverse transcriptase domain inhibit RT activity.
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PMID:Properties of avian retrovirus particles defective in viral protease. 169 12

A series of 9-aminoacridine carboxamide derivatives of systematically varied structure was assayed in an RNA synthesis in vitro system. Escherichia coli DNA-dependent RNA polymerase and DNA derived from phage T7 or calf thymus were used to measure the effect of the drugs on overall RNA and the initiating dinucleotide (pppApU) syntheses. By means of multiple linear regression analysis it was shown that the inhibition of these reactions depends both on the drug equilibrium binding constant and kinetic parameters of dissociation of drug-DNA complexes.
Acta Biochim Pol 1990
PMID:Inhibition of RNA synthesis in vitro by 9-aminoacridine carboxamide antitumor agents. Effects on overall RNA synthesis and synthesis of the initiating dinucleotide. 170 40

The central part of bacteriophage T4 baseplate is built of several proteins which are present in only a few copies per phage particle. Only some of these minor baseplate components have been identified previously as distinct protein species by biochemical analysis. We have used the bacteriophage T7 RNA polymerase expression system to identify and overexpress the minor baseplate proteins. The products of genes 25, 26 and 51 were identified on the autoradiographs after selective labelling with [35]S methionine. The overexpression of gene 25 and 51 products was high enough to make possible undertaking their purification and studies of their properties.
Acta Biochim Pol 1991
PMID:Expression of bacteriophage T4 minor baseplate proteins in the bacteriophage T7 promoter/RNA polymerase expression system. 179 11

We present evidence that the genes encoding U3 snRNA in plants are transcribed by RNA polymerase III (pol III) and not by RNA polymerase II (pol II) as in vertebrates or lower eukaryotes. The U3 gene is the only known example of a gene transcribed by different polymerases in different organisms. It is possible to convert the plant U3 gene into a functional pol II-transcribed gene by manipulating the spacing between the promoter elements and inserting a pol II-specific termination signal. Pol II-transcribed U3 RNA, containing the 5'-terminal cap different from that present in the wild-type counterpart, is packaged in transfected protoplasts into U3 snRNP precipitable with anti-fibrillarin antibodies. These findings provide further evidence for the common ancestry of the pol II and pol III transcription systems, and indicate that promoter diversification in some genes has occurred relatively recently.
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PMID:Alteration of the RNA polymerase specificity of U3 snRNA genes during evolution and in vitro. 182 60

We found that lambda plasmid replication, as measured by the increase in plasmid content per bacterial mass, proceeds for hours in an amino acid-starved, relaxed mutant of Escherichia coli K-12, whereas is inhibited in its wild-type stringent partner. Replication of lambda plasmid in amino acid-starved, relaxed cells reveals absolute lambda O dependence and is not inhibited by chloramphenicol at 200 micrograms/ml. The replication also occurs in wild-type cells treated with chloramphenicol. We conclude that lambda plasmid replication is under stringent control, probably as a result of the action of ppGpp, the signal for the stringent response, on RNA polymerase.
Acta Biochim Pol 1991
PMID:Replication of lambda plasmid in amino acid-starved strains of Escherichia coli. 183 19

Human B lymphocytes latently infected with Epstein-Barr virus (EBV) synthesize very large amounts (5 x 10(6)/cell) of two small nuclear RNAs called EBERs (Epstein-Barr encoded RNAs). These RNAs are of unknown function and, like many RNA polymerase III (Pol III) transcripts, bind the La autoantigen. We have discovered that the EBERs also associate with a second highly abundant host-encoded protein designated EAP (EBER associated protein). Human EAP is a small (14,777 dalton, 128 amino acid) polypeptide that binds both EBER 1 and EBER 2. EAP is also found in association with one or both of two analogous virally-encoded RNAs found in baboon cells infected with herpesvirus papio (HVP). We have devised a purification procedure for EAP and have cloned its cDNA from a human placental cDNA library using amino acid sequence data and the polymerase chain reaction (PCR). The predicted amino acid sequence of EAP shows a strong resemblance (77% identity) to an endodermal, developmentally regulated sea urchin protein called 217 (Dolecki et al., 1988). EAP contains a potential nuclear localization signal and a highly acidic carboxy terminus, but does not display marked similarity to any other RNA binding proteins.
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PMID:EAP, a highly conserved cellular protein associated with Epstein-Barr virus small RNAs (EBERs). 184 7

The c-myc promoter has the unusual property of displaying both RNA polymerase II (Pol II) and RNA polymerase III (Pol III) activities. Both Pol II and Pol III utilize the same transcription initiation site. We have now examined the effects of mutations in crucial regions of the c-myc promoter to assess their effects on both transcriptional activities. In doing this we show that both Pol II and Pol III activities require sequences that are located within the stronger of the two principal c-myc promoter regions (P2). Further, we show that the Pol III activity using this initiation site does not require an A box or distal upstream sequences. Like the Pol II activity, it does require an intact TATA sequence and alterations at this site result in the simultaneous loss of both Pol II and Pol III activities. The superimposition of two apparently inseparable promoter activities makes it possible to consider common features, possible common protein elements in each holoenzyme complex, as well as a potential role for each enzyme in the regulated expression of the c-myc gene.
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PMID:In vitro and in vivo analysis of the c-myc RNA polymerase III promoter. 192 71

Using an in vitro transcription system for Saccharomyces cerevisiae RNA polymerase I, we have analyzed Pol I promoter deletion mutants and mapped the boundaries of the promoter between positions -155 and +27. The 5'-boundary of the minimal core promoter capable of transcription initiation, however, was found to lie between -38 and -26. The 3'-deletion extending to -2 and -5 still allowed some transcription, suggesting that the positioning of Pol I is directed by upstream sequences. The results of in vitro analysis of linker scanning mutants (LSMs) combined with the deletion analysis showed that the promoter consists of three domains: two essential core domains (I: -28 to +8 and II: -76 to -51) and a transcription modulating upstream domain (III: -146 to -91). These results are in general agreement with those obtained in vivo (1). Using a template competition assay we also analyzed these mutant promoters for their ability to form a stable preinitiation complex. We found that the ability of 5'-deletion mutants to sequester an essential factor(s) correlates with their transcriptional activity. In contrast, several 3'-deletions and some LSMs in domain I and II decrease transcription activity greatly without significantly decreasing competition ability. The results indicate that the stimulatory function of domain III is achieved through its interaction with an essential transcription factor(s), although the other domains also participate in this interaction, perhaps directly or through another protein factor.
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PMID:The yeast RNA polymerase I promoter: ribosomal DNA sequences involved in transcription initiation and complex formation in vitro. 192 20

The plus strand of the L-A double-stranded RNA virus of Saccharomyces cerevisiae has two large open reading frames, ORF1, which encodes the major coat protein, and ORF2, which encodes a single-stranded RNA-binding protein having a sequence diagnostic of viral RNA-dependent RNA polymerases. ORF2 is expressed only as a Gag-Pol-type fusion protein with ORF1. We have constructed a plasmid which expresses these proteins from the yeast PGK1 promoter. We show that this plasmid can support the replication of the killer toxin-encoding M1 satellite virus in the absence of an L-A double-stranded RNA helper virus itself. This requires ORF2 expression, providing a potential in vivo assay for the RNA polymerase and single-stranded RNA-binding activities of the fusion protein determined by ORF2. ORF1 expression, like a host ski- mutation, can suppress the usual requirement of M1 for the MAK11, MAK18, and MAK27 genes and allow a defective L-A (L-A-E) to support M1 replication. These results suggest that expression of ORF1 from the vector makes the cell a ski- phenocopy. Indeed, expression of ORF1 in a wild-type killer makes it a superkiller, suggesting that a target of the SKI antiviral system may be the major coat protein.
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PMID:Expression of yeast L-A double-stranded RNA virus proteins produces derepressed replication: a ski- phenocopy. 198 95

The transcription mode of the Xenopus tRNA(Ser)Sec gene by RNA polymerase III was deciphered by injection of mutant templates into Xenopus oocyte nuclei. tRNA(Ser)Sec represents the paradigm of a new class of RNA polymerase III genes combining tRNA and U snRNA gene regulatory elements. Its promoter is tripartite, constituted by two upstream elements, a PSE and a TATA motif that are interchangeable with those of U6 snRNA genes and an internal box B as in other tRNAs. The B box enables the transcription level dependent on the upstream promoter to be increased. Data obtained indicate that U1 snRNA (Pol II) and tRNA(Ser)Sec (Pol III) genes share at least one transcription factor, implying that the border between transcription systems is less tight than expected.
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PMID:Transcription of the Xenopus laevis selenocysteine tRNA(Ser)Sec gene: a system that combines an internal B box and upstream elements also found in U6 snRNA genes. 200 75


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