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:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The influence of a double-stranded region on DNA synthesis performed by a series of DNA polymerases on a single-stranded template was studied. Two types of double-stranded hindrances were employed: a stable hairpin formed by the template alone and a region formed by the template and an extraneous oligonucleotide complementary to the template. While T4 and calf thymus alpha DNA polymerases are strongly arrested at the beginning of either of the two double-stranded hindrances, the Klenow fragment of E. coli DNA polymerase I and avian myeloblastosis virus reverse transcriptase can pass through the double-stranded regions. The DNA chain-elongation rate seems to be undisturbed in the case of reverse transcriptase but greatly reduced for DNA polymerase I.
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PMID:The influence of a double-stranded hindrance on DNA synthesis performed by DNA polymerase alpha, T4 DNA polymerase, DNA polymerase I (Klenow fragment) and AMV reverse transcriptase. 244 62

Reverse transcriptase was purified from human immunodeficiency virus (HIV). It utilized the artificial primer-template poly(rA)-oligo(dT)12-18 more efficiently than activated calf thymus DNA, poly(rI)-oligo(dC)12-18, poly(rC)-oligo(dG)12-18, or poly(rCm)-oligo(dG)12-18. Maximum activity was observed at pH 7.0 to 7.6 in the presence of 5 mM MgCl2 and 100 mM KCl. 3'-Azido-3'-deoxythymidine triphosphate competed with dTTP for binding to HIV reverse transcriptase. Different kinetic constants were obtained with different primer-templates. Km and Ki values of 2.8 and 0.04 microM, respectively, were obtained with poly(rA)-oligo(dT)12-18. The corresponding values were 1.2 and 0.3 microM, respectively, with activated calf thymus DNA and 0.3 and 0.01 microM, respectively, with extracted virus and native template. Inhibition of the host cell DNA polymerases alpha and beta was considerably weaker. The Km and Ki values obtained with activated calf thymus DNA as the primer-template were 2.4 and 230 microM, respectively, for DNA polymerase alpha and 6.0 and 73 microM, respectively, for DNA polymerase beta. 3'-Azido-3'-deoxythymidine triphosphate could also serve as an alternate substrate for HIV reverse transcriptase. The resulting incorporation of 3'-azido-3'-deoxythymidine triphosphate into poly(rA)-oligo(dT)12-18 caused chain termination and premature deceleration of the reaction. The terminated primer could not be elongated when incubated with dTTP and HIV reverse transcriptase.
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PMID:3'-Azido-3'-deoxythymidine triphosphate as an inhibitor and substrate of purified human immunodeficiency virus reverse transcriptase. 244 66

The addition of monosialoganglioside GM1 to serum-free culture medium efficiently and specifically inhibited CD4 antigen expression on normal T lymphocytes from peripheral blood or thymus as well as on cells from H9 and Molt-3 lines; other molecules such as CD3, CD2 and CD8 were not affected. Subsequent addition of fetal calf serum or bovine and human serum albumin blocked GM1 action on CD4 expression, most likely through the formation of ganglioside-albumin complexes. Removal of GM1 from the medium was followed by the prompt reappearance of CD4 on the cell surface. GM1 treatment of H9 and Molt-3 cells greatly reduced HIV-1 infectivity, which was evaluated by reverse transcriptase activity levels in culture supernatants and p24 detection on target cells. GM1 also inhibited syncytial formation in Molt-3 cells even when treatment was initiated 24h after infection. The GM1 effect on HIV-1 infectivity, however, was not long-lasting since removal of the compound was followed by a rapid increase in viral replication, probably due to CD4 re-expression and HIV-1 propagation from a few initially infected cells.
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PMID:CD4 modulation and inhibition of HIV-1 infectivity induced by monosialoganglioside GM1 in vitro. 247 63

We have investigated the ability of some nucleoside 5'-triphosphate analogues to terminate the DNA synthesis catalyzed by calf thymus DNA polymerase alpha and terminal deoxynucleotidyl transferase, rat liver DNA polymerase beta, E. coli DNA polymerase I (Klenow's fragment) and AMV reverse transcriptase. It has been shown that lyxoanhydronucleoside 5'-triphosphates terminate DNA synthesis catalyzed by reverse transcriptase and terminal deoxynucleotydil transferase. 2',3'-O-Isopropylidenecytidine 5'-triphosphate inhibits the DNA synthesis catalyzed by reverse transcriptase and DNA polymerase beta and its moiety was incorporated in the place of dTMP residue. Riboanhydroadenosine 5'-triphosphate reveals the properties of an effective termination substrate for all the DNA polymerases studied. This is the first attempt to investigate nucleotide analogues with the restricted conformation of the carbohydrate moiety as termination substrates for several prokaryotic and eukaryotic DNA polymerases.
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PMID:[Conformation limited nucleoside-5'-phosphates as termination substrates for DNA-polymerases]. 248 45

Castanospermine (1,6,7,8-tetrahydroxyoctahydroindolizine), an inhibitor of glycoprotein processing, has been shown to inhibit the human immunodeficiency virus type 1 (HIV-1) with acceptable toxicity in cultured cells. In contrast to reverse transcriptase inhibitors, castanospermine targets host enzymes. We have analyzed castanospermine in murine systems, using cultured cells as well as live animals. Plaque formation by Rauscher murine leukemia virus (RLV) was inhibited with a median inhibitory concentration (IC50) of 2 micrograms/ml. RLV-exposed BALB/c mice treated with a 20 day course of castanospermine starting 4 h postinoculation showed a dose-dependent inhibition of splenomegaly. Oral castanospermine therapy given to chronically RLV-infected mice prolonged median survival from 36 to 94 days when compared to untreated controls (p = 0.007). Castanospermine was better tolerated orally than intraperitoneally at the same dose. Toxic effects included weight loss, lethargy, and dose-dependent thrombocytopenia. At the highest intraperitoneal dose, lymphoid depletion occurred in thymus, spleen, and lymph nodes. We conclude that castanospermine is an active antiviral agent in animals and that prolonged oral administration is tolerable; however, when compared to 3'-azido-3'-deoxythymidine in the same murine system, castanospermine was less active and more toxic.
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PMID:In vivo analysis of castanospermine, a candidate antiretroviral agent. 249 48

The reaction of pyrophosphorolysis catalyzed by Escherichia coli DNA polymerase I Klenov fragment, calf thymus DNA polymerase alpha, rat liver DNA polymerase beta and AMV reverse transcriptase was studied. Some pyrophosphate (PPi) analogs were taken as low molecular weight substrates. It was shown that only imidodiphosphonic acid acted as the PPi substrate analog for the reactions catalyzed by DNA polymerases I and alpha, both imidodiphosphonic acid and methylenediphosphonic acid were active in the case of DNA polymerase beta and reverse transcriptase. Other analogs tested were neither nucleotide residue acceptors, nor inhibitors of the pyrophosphorolysis reaction with PPi. The abilities of some PPi analogs to inhibit the DNA elongation catalyzed by reverse transcriptase were investigated. The principles of specificity of low molecular substrates recognition by DNA polymerases and some problems concerning the mechanisms of DNA synthesis inhibition by PPi analogues are discussed.
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PMID:[Analogs of pyrophosphate in a pyrophosphorolysis reaction catalyzed by DNA polymerases]. 254 2

It is shown that dNTP(3'F) are terminators of DNA synthesis and may serve as very effective tools for DNA sequencing with E.coli DNA polymerase I and AMV reverse transcriptase. The dNTP(3'F) are found to be chain terminator substrates for calf thymus terminal deoxyribonucleotidyl transferase but not for calf thymus DNA polymerase alpha. The optimal dNTP(3'F) concentration for DNA sequencing by DNA polymerase I is found to be an order of magnitude lower than that of ddNTPs. dNTP(3'F) produce a more clear sequence pattern than do ddNTPs.
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PMID:3'-Fluoro-2',3'-dideoxyribonucleoside 5'-triphosphates: terminators of DNA synthesis. 258 Jul 38

A number of nucleoside 5'-triphosphate analogs were tested with Escherichia coli DNA polymerase I and Klenow fragment of the enzyme, bacteriophage T4 DNA polymerase and calf thymus DNA polymerase alpha. It was shown that 3'-amino-2',3'-dideoxynucleoside 5'-triphosphates as well as a number of 3'-derivatives of dTTP(3'NH2) are able to terminate DNA synthesis catalyzed by each enzyme if the reaction is performed in the absence of natural substrates. ddNTP and dNTP(3'F) were found to be inactive with DNA polymerase alpha only, but araNTP(3'NH2) was inactive with E. coli DNA polymerase I. dTTP(3'N3), dGTP(3'N'3), dCTP(3'N3), araNTP(3'N3) and (alpha-thio)dTTP(3'F) were unable to inhibit any of the above-mentioned DNA polymerases, in contrast to reverse transcriptase, accessible to the most nucleotide analogs tested.
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PMID:Nucleoside 5'-triphosphates with modified sugars as substrates for DNA polymerases. 302 Dec 25

Bovine leukemia provirus is reported to be integrated in the DNA of different infected mammalian cells. We observed morphological transformation in BLV infected sheep fetal spleen, kidney, thymus and sternal cultures. The presence of BLV specific sequences in their genome was established after digestion with the restriction endonuclease EcoRI and hybridization with a BLV specific probe. Human myeloma ARH77 and myeloid K562 cells infected with BLV were virus productive as detected by a reverse transcriptase assay. The presence of proviral sequences was confirmed after Southern blotting analysis. Restriction digestion by SacI enzyme yielded a complete 8.9 kb BLV provirus in infected ARH77 cells and a smaller 7.5 kb BLV fragment in infected K562 cells.
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PMID:Bovine leukemia provirus in the DNA of different infected host cells. 302 95

2',3'-Dideoxy-2',3'-dehydrothymidine 5'-triphosphate (dddTTP) reveals the termination substrate properties in the DNA synthesis catalyzed by E. coli polymerase I (Klenow fragment), rat liver DNA polymerase beta, calf thymus terminal deoxynucleotidyl transferase, and reverse transcriptase of avian myeloblastosis virus but does not affect calf thymus DNA polymerase alpha. For DNA polymerase I, dddTTP by an order of magnitude is more effective than any known termination substrate. It is supposed that dddTTP models the conformational state of the substrate's carbohydrate moiety in the complex DNA polymerase + template-primer.
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PMID:[A new terminator of DNA biosynthesis--possible conformation analog of the substrate in a DNA-synthesizing complex]. 343 58


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