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)

A novel expression system based on coinfection of cells with two recombinant vaccinia viruses has been developed. One recombinant vaccinia virus contained the bacteriophage T7 RNA polymerase gene under control of a vaccinia virus promoter. The second recombinant vaccinia virus contained a target gene of choice flanked by bacteriophage T7 promoter and termination sequences. Maximum expression of the target gene occurred when cells were infected with 10 PFU of each recombinant virus. Although T7 RNA polymerase synthesis began shortly after infection, the target gene was not expressed until late times and was largely inhibited when DNA replication was blocked. Target gene transcripts were analyzed by agarose gel electrophoresis and had the predicted size. With this system, Escherichia coli beta-galactosidase, hepatitis B virus surface antigen, and human immunodeficiency virus envelope proteins were made. In each case, the level of synthesis was greater than had previously been obtained with the more conventional recombinant vaccinia virus expression system.
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PMID:Use of a hybrid vaccinia virus-T7 RNA polymerase system for expression of target genes. 311 59

We have previously shown by affinity chromatography that RAP30 and RAP74 are the mammalian proteins that have the highest affinity for RNA polymerase II. Here we show that RAP30 binds to RAP74 and that the RAP30-RAP74 complex (RAP30/74) is required for accurate initiation by RNA polymerase II. RAP30/74 is required for accurate transcription from the following promoters: the adenovirus major late promoter, the long terminal repeat of human immunodeficiency virus, P2 of the human c-myc gene, the mouse beta maj-globin promoter (all of which have TATA boxes), and the mouse dihydrofolate reductase promoter (which lacks a TATA box). RAP30/74 is not required for initiation by RNA polymerase III at the adenovirus virus-associated RNA promoters. Therefore, RAP30/74 is a general initiation factor that binds to RNA polymerase II.
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PMID:RAP30/74: a general initiation factor that binds to RNA polymerase II. 338 90

Human immunodeficiency virus (HIV), formerly termed human T-lymphotropic virus (HTLVIII/LAV), is the etiological agent of acquired immune deficiency syndrome (AIDS). Direct detection of HIV-1 nucleic acid sequences in patient tissue or blood samples is possible in only a minor fraction of cases due to the low percentage of infected cells (Shaw et al., 1984). We report a modification of the polymerase chain reaction method (PCR) (Saiki et al., 1985), in which we amplify sequences from HIV-1 RNA templates, for the identification of HIV-1 in peripheral blood and tissue samples obtained from AIDS and AIDS-related complex (ARC) patients. This method of HIV-1 detection is at least six orders of magnitude more sensitive than standard nucleic acid detection methods and has direct clinical applications. In vitro tissue culturing of the virus is not required for HIV-1 detection. Using this technique, the sequence in the orfB region of HIV-1 has been amplified and detected from less than 1 microgram of total RNA prepared from a few milliliters of peripheral blood samples. This technique enables the rapid and unambiguous clinical detection of potential HIV-infected individuals and can be used to assay the efficacy of anti-HIV-1 drugs. To enhance the efficiency of this technique, we have appended the prokaryotic T7 RNA polymerase promoter sequence to one of the priming oligonucleotides. After several cycles of PCR with the promoter-containing oligo, a small aliquot of the reaction can be utilized to direct specific and efficient T7 RNA polymerase-mediated transcription of the amplified sequences, thus enhancing the sensitivity and simplifying the labor of the experiment.
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PMID:Direct detection of HIV-1 RNA from AIDS and ARC patient samples. 339 53

Permanently established human cell lines can produce several retroviruses. It is important to routinely test such cell lines for human T cell lymphotropic virus (HTLV) type I and II, and for human immunodeficiency virus (HIV) type 1 and 2 in order to exclude any potential biohazard from cell lines producing human retroviruses. Reverse transcriptase assay, polymerase chain reaction, and dot-blot hybridization of in-vitro amplified DNA with virus-specific probes are used.
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PMID:Retrovirus tests of human leukemia/lymphoma cell lines at DSM. 750 50

Reverse transcriptase (RT) is an indispensable component of infectious retroviruses. We have developed an ultrasensitive RT test in which RNA of bacteriophage MS2 serves as the template for RT-mediated cDNA synthesis. A fragment of the cDNA is selectively amplified by polymerase chain reaction and the amplification product is analyzed by Southern blot hybridization or enzyme immunoassay. The procedure was 10(6) to 10(7) times more sensitive than a conventional RT test and detected as little as 10(-9) unit of murine leukemia virus RT, which corresponded to 2.1 x 10(2) molecules, a number present in 3-11 virions. As a screening assay for filterable particle-associated RT, it was positive with supernatants from cell cultures producing human immunodeficiency virus (HIV) type 1 or human T-cell leukemia virus (HTLV) type 1 or 2, but was negative with nonproducer cultures. It was positive with plasma samples from all tested individuals infected with HIV-1, HIV-2, or HTLV-1 and sera from cats infected with feline leukemia virus or feline immunodeficiency virus. Control samples from blood donors or uninfected cats were negative. Density banding experiments with culture supernatants showed that the RT activity was associated with virus particles. The assay should detect all replication-competent retroviruses or similar agents. It may be used as a screening assay for such agents, for quantitation of the viral load, drug susceptibility testing of RT, and control of virus inactivation in biological products.
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PMID:Ultrasensitive retrovirus detection by a reverse transcriptase assay based on product enhancement. 750 77

Inophyllums are novel non-nucleoside inhibitors of human immunodeficiency virus (HIV) type 1 reverse transcriptase identified through an enzyme screening program and isolated from the plant Calophyllum inophyllum. The kinetics of reverse transcriptase inhibition by inophyllum B were characterized using recombinant purified enzyme, a heteropolymeric RNA template, and a scintillation proximity assay. Preincubation of inhibitor with the enzyme-template-primer complex for 11 min was required for maximal inhibition of reverse transcriptase to occur, suggesting that inophyllum B had a slow on-rate and that template-primer must bind to reverse transcriptase prior to inhibitor binding. Inhibition of reverse transcriptase by inophyllums was shown to be reversible. When thymidine triphosphate was the variable substrate, inophyllum B inhibited reverse transcriptase noncompetitively with a Ki of 42 nM. Enzyme inhibition with respect to template-primer was uncompetitive with a Ki of 26 nM. Reverse transcriptase enzymes containing point mutations in which tyrosine 181 was changed to either cysteine or isoleucine exhibited marginal resistance to inophyllums but were resistant to (+)-(5S)-4,5,6,7-tetrahydro-9-chloro-5-methyl-6- (3-methyl-2-butenyl)-imidazo[4,5,1-j,k][1,4]benzodiazepin-2-(1H)-t hione (TIBO R82913). A mutant enzyme in which tyrosine 188 was changed to leucine was cross-resistant to both inophyllum B and TIBO R82913, as was HIV type 2 reverse transcriptase. These studies suggest that inophyllum B and TIBO R82913 bind to distinct but overlapping sites. Inhibition of avian myeloblastosis virus reverse transcriptase and Moloney murine leukemia virus reverse transcriptase by inophyllum B was detectible, suggesting that these inhibitors may be more promiscuous than other previously described non-nucleoside inhibitors. Inophyllums were active against HIV type 1 in cell culture with IC50 values of approximately 1.5 microM. These studies imply that the inophyllums have a novel mechanism of interaction with reverse transcriptase and as such could conceivably play a role in combination therapy.
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PMID:Kinetic and mutational analysis of human immunodeficiency virus type 1 reverse transcriptase inhibition by inophyllums, a novel class of non-nucleoside inhibitors. 750

Based on the crystallographic structure of the active site in the reverse transcriptase (RT) of human immunodeficiency virus (HIV), a group of hydrophobic polyadenylic acid (5') derivatives were designed and synthesized as inhibitors of the enzyme. These compounds were found to inhibit all six of the RTs tested, with IC50 = 10(-11)-10(-8) M, but did not inhibit either RNA polymerase II (even at 10(-5) M) or DNA polymerase I up to 10(-6) M inhibitor concentration. The underivatized poly(A) did not inhibit any of the RTs tested under the same conditions. In aqueous solutions of purified HIV-1 RT, poly-2'-O-(2,4-dinitrophenyl)-oligo(A) was found to inhibit the enzyme reversibly and compete with the primer-template poly(A)-(dT)12, whereas poly-2'-O-(3-fluoro-4,6-dinitrophenyl)-poly(A) was found to inactivate HIV-1 RT irreversibly by covalent labeling. A comparison of physicochemical properties of the hybrids poly(A)-poly(dT) and dinitrophenyl-poly(A)-poly(dT) shows that the hydrophobic dinitrophenyl groups stabilize double helical structures. These inhibitors were also found to be effective in keeping susceptible lymphocytes viable in the presence of HIV-1 (wild type). The effective inhibitor concentrations (EC50) were found to be 0.2-2.6 microgram/ml. No toxic effect on the host cells was found even at 100-1000-fold higher inhibitor concentrations.
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PMID:Design of structure-based reverse transcriptase inhibitors. 751 57

Reverse transcriptase from feline immunodeficiency virus (FIV) has been cloned and expressed in Escherichia coli. We have purified this recombinant enzyme and shown that it is a 66-kDa protein that is indistinguishable from virion-derived FIV reverse transcriptase in sensitivity to the 5'-triphosphates of 3'-azido-3'-deoxythymidine and the four 2',3'-dideoxynucleosides. The availability of large quantities of the FIV reverse transcriptase will allow more detailed physical and pharmacological studies.
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PMID:Expression of reverse transcriptase from feline immunodeficiency virus in Escherichia coli. 751 59

The fundamental role played by reverse transcriptase in the replication of retroviruses has stimulated the study of the mechanism of action of this enzyme. The reverse transcriptase of the type 1 human immunodeficiency virus forms a stable complex with its cognate transfer RNA replication primer (tRNA(Lys3)). Here, we outline the role of this enzyme in the selection of its primer tRNA, the annealing of primer tRNA to the complementary region of the retroviral genome, and the first attempts to use the reverse-transcriptase-tRNA complex as a new target for antiviral agents.
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PMID:Priming of HIV replication by tRNA(Lys3): role of reverse transcriptase. 751 21

Two ternary complexes of rat DNA polymerase beta (pol beta), a DNA template-primer, and dideoxycytidine triphosphate (ddCTP) have been determined at 2.9 A and 3.6 A resolution, respectively. ddCTP is the triphosphate of dideoxycytidine (ddC), a nucleoside analog that targets the reverse transcriptase of human immunodeficiency virus (HIV) and is at present used to treat AIDS. Although crystals of the two complexes belong to different space groups, the structures are similar, suggesting that the polymerase-DNA-ddCTP interactions are not affected by crystal packing forces. In the pol beta active site, the attacking 3'-OH of the elongating primer, the ddCTP phosphates, and two Mg2+ ions are all clustered around Asp190, Asp192, and Asp256. Two of these residues, Asp190 and Asp256, are present in the amino acid sequences of all polymerases so far studied and are also spatially similar in the four polymerases--the Klenow fragment of Escherichia coli DNA polymerase I, HIV-1 reverse transcriptase, T7 RNA polymerase, and rat DNA pol beta--whose crystal structures are now known. A two-metal ion mechanism is described for the nucleotidyl transfer reaction and may apply to all polymerases. In the ternary complex structures analyzed, pol beta binds to the DNA template-primer in a different manner from that recently proposed for other polymerase-DNA models.
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PMID:Structures of ternary complexes of rat DNA polymerase beta, a DNA template-primer, and ddCTP. 752 45


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