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:2.7.7.7 (DNA polymerase)
17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cocultivation of spleen cells from the Southeast Asian mouse, Mus cervicolor, with heterologous cell lines has permitted the isolation of a new retravirus (designated M432) that can be transmitted to tissue culture cells of the laboratory mouse, M. musculus. Cells infected with M432 contain cytoplasmic type A particles and budding forms with compact,spherical nucleoids; extracellular virions lack surface spikes and have a condensed, central core surrounded by an intermediate line. Like other retraviruses, M432 bands isopycnically in sucrose at 1.16-1.17 g/cm3 and contains a 70S RNA genome composed of 35S subunits and an RNA-dependent DNA polymerase (RNA-dependent DNA nucleotidyltransferase). The viral reverse transcriptase requires magnesium as a cofactor and transcribes the synthetic template:primer poly(rC)-oligo(dG) more efficiently than poly(rA)-oligo(dT). [3H]DNA transcripts of the viral RNA genome detect multiple copies of endogenous virogene sequences in the cellular DNA of normal M. cervicolor, and fewer copies in heterologous cells infected with M432. Partially related nucleic acid sequences are also detected in the DNA of M. caroli and M. musculus as well as in more distantly related species (rat and hamster), reflecting the evolutionary conservation of these gene sequences in rodents. Although the virus from M. cervicolor shares certain morphologic and biochemical properties with murine type B viruses, the new isolate is unrelated by nucleic acid hybridization criteria to the mouse mammary tumor virus, the bovine leukemia virus, the Mason-Pfizer monkey virus, or known murine type C viruses, including endogenous type C viruses isolated from M. cervicolor.
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PMID:A new class of genetically transmitted retravirus isolated from Mus cervicolor. 6 62

For attempt to detect an etiological agent, cultures from bovine lymphosarcoma cases (adult form (ALS), calf form (CLS), and thymic form (TLS) were maintained in vitro for over a 18 month period. In two cultures from ALS, bovine leukemia virus (BLV) antigen was constantly detected. On the other hand, BLV antigen remained negative in cultures from two CLS and one TLS cases up to 40 passages. The RNA dependent DNA polymerase activities in these cultures were also negative. Treatment of a culture from CLS (3178) originated from liver tumor with 5'-iodo-2'-deoxyuridine (IdU) and dexamethasone (DXM) resulted in production of an agent serologically and morphologically similar to BLV and in alteration of cell morphology. No virus was detected in culture from TLS after treatment with IdU and DXM.
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PMID:Induction of C-type virus in cell lines derived from calf form bovine lymphosarcoma. 8 38

An RNA-directed DNA polymerase was purified from bovine leukemia virus (BLV) by successive glycerol gradient centrifugation, column chromatography on phosphocellulose and gel filtration on Sephadex G-200. The purified DNA polymerase transcribes heteropolymeric regions of 30--40 S RNA isolated from avian myeloblastosis virus. The enzyme differs from other known DNA polymerases of mammalian type-C RNA tumor viruses by the following properties: 1. Its apparent molecular weight as estimated by velocity sedimentation data is 58,000 at 0.12 M KCl and 43,000 in the presence of 0.50 M KCl. 2. It has a Mg2+ optimum of 10 mM, and a Mn2+ optimum of 0.25 mM with (rA)n-(dT)10 as template. 3. At 50 mM KCl it is inhibited more than 70%, but it is not inhibited by phosphate ions at 2 mM. These properties confirm the peculiar position of BLV within the family Retraviridae.
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PMID:Purification and characterization of bovine leukemia virus DNA polymerase. 23 43

Genetic variation of the Bovine Leukemia Virus (BLV) appears to be limited in vitro and during the latent phase of the disease. However, cells in tumors often harbor deleted proviruses that are defective for expression. In order to gain insight into the involvement of viral genetic variation during pathogenesis, the BLV LTR and the env proviral sequences were analyzed in tumor tissues. A sheep (M230) was injected with the cloned BLV provirus 344 and became persistently infected with circulating lymphocytes reaching 345,000/mm3. After 11 months, this infected sheep developed leukemia-lymphoma. DNA was extracted from peripheral blood leukocytes at the time of tumor development and the LTR and the env gene were amplified, using the polymerase chain reaction procedure, cloned, and sequenced. Twenty independent LTR and twenty env clones were analyzed. It appeared that the in vivo mutation rate in the env gene was 0.043% (eight mutations including seven transitions out of 18,300 bp). Five point mutations (all transitions) were identified in the LTR, corresponding to 0.041% modifications (four mutations out of 9740 bp). These mutation rate values (0.043 and 0.041) were close to those due to the Taq DNA polymerase errors (0.030%). Altogether, these data demonstrate the lack of genetic variation in the LTR and the env gene during this case of BLV-induced pathogenesis in vivo. They confirm that the defectiveness of some BLV proviruses in vivo, thus, is not a mandatory step in the leukemogenic process.
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PMID:Lack of LTR and ENV genetic variation during bovine leukemia virus-induced leukemogenesis. 783 40

Complex oncoviruses contain, in addition to the classical retroviral genes (gag, pol, and env), a region (X) located between the envelope sequences and the 3' long terminal repeat. The X region contains two genes, tax and rex, whose protein products are involved in transcriptional and posttranscriptional regulation of viral expression. In addition to these activators, the bovine leukemia virus (BLV) and the human T-cell leukemia virus (HTLV) contain alternative open reading frames (R3 and G4 for BLV; p30, p13, and p12 for HTLV). As a virus/animal model for HTLV-induced leukemogenesis, BLV provirus can be injected intradermally into sheep, where it induced B-lymphocyte transformation. Deletion of the R3 and G4 sequences from an infectious and tumorigenic BLV provirus greatly impaired the in vivo propagation of the viruses as demonstrated by DNA polymerase chain reaction, RNA blots, structural-protein ELISA, and immunofluorescence analysis. Our results show that the alternative open reading frames are required for maintaining high virus loads during the course of persistent infection in vivo. Thus, R3 and G4 are candidates for antiviral drug development. Furthermore, viruses with a deletion in these sequences should be tested as live attenuated vaccines.
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PMID:Attenuation of bovine leukemia virus by deletion of R3 and G4 open reading frames. 797 96

Intradermal injection of a cloned bovine leukemia virus (BLV) provirus (pV344) into sheep allowed direct evaluation of intrastrain variability. A sheep was injected with pV344 DNA mixed with DEAE-dextran and became persistently infected with BLV strain 344. After 18 months, DNA was extracted from peripheral blood leukocytes from a single 0.5-ml blood sample. The long terminal repeat (LTR) and the env gene were amplified by using the polymerase chain reaction, cloned, and sequenced. Nineteen independent LTR clones (0.6-kb inserts) and 16 env clones (1-kb inserts) were analyzed. The in vivo rate of nucleotide change was 0.009%/year (two mutations out of 14,464 bp in 1.5 years), corresponding to only one amino acid change in the env gene. Five point mutations (all transitions), corresponding to a modification rate of 0.034%/year (five mutations out of 9,709 bp in 1.5 years), were identified in the LTR. As a control for Taq DNA polymerase errors, the same procedure using pV344 plasmid DNA was carried out. Out of 9,944 bp sequenced, three point mutations were found (i.e., one misincorporation in 3,315 nucleotides). These data demonstrate the extremely low level (or absence) of intrastrain variability of BLV in vivo. Consequently, BLV persistence in the infected host does not seem to result from an escape mutant strategy, in sharp contrast with the high mutation rates observed in the lentivirus family. The lack of genetic variation supports the possibility of successful vaccine against BLV and probably against the related human T-cell leukemia viruses.
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PMID:Bovine leukemia virus, an animal model for the study of intrastrain variability. 838 Apr 55

The reverse transcriptase-RNA dependent DNA polymerase of Bovine Leukemia Virus (BLV) was isolated and characterized. The enzyme has a molecular weight of about 80kd and the isoelectric point is 7.6. The enzyme prefers magnesium, as a divalent cation using synthetic homopolymeric template primer poly (C) oligo (dG). Monoclonal antibodies directed against reverse transcriptase of human immunodeficiency virus type I (HIV-I) did not crossreact with the isolated polymerase.
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PMID:Characterization of the RNA dependent DNA polymerase of bovine leukemia virus. 891 42

Degenerate PCR primers which amplify a conserved region of the DNA polymerase genes of the herpesvirus family were used to provide sequence evidence for a new bovine herpesvirus in bovine B-lymphoma cells and peripheral blood mononuclear cells (PBMC). The sequence of the resultant amplicon was found to be distinct from those of known herpesvirus isolates. Alignment of amino acid sequences demonstrated 70% identity with ovine herpesvirus 2, 69% with alcelaphine herpesvirus 1, 65% with bovine herpesvirus 4, and 42% with bovine herpesvirus 1. Phylogenetic analysis placed this putative virus within the tumorigenic Gammaherpesvirinae subfamily, and it is tentatively identified as bovine lymphotropic herpesvirus. This novel agent was expressed in vitro from infected PBMC, and cell-free supernatants were used to transfer infection to a bovine B-cell line, BL3. Analysis, with specific PCR primers, of DNA from bovine PBMC and lymphoma cells identified infection in blood of 91% of adult animals (n = 101), 63% of lymphomas (n = 32), and 38% of juveniles (n = 13). Of the adults, herpesvirus infection was present in 94% of animals that were seropositive for bovine leukemia virus (BLV) (n = 63) and in 87% of BLV-seronegative animals (n = 38). Of the seropositive group, 17 animals exhibited persistent lymphocytosis, and 100% of these were herpesvirus positive by PCR. A role for bovine lymphotropic herpesvirus as a cofactor in BLV pathogenesis is considered.
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PMID:Detection of a novel bovine lymphotropic herpesvirus. 955 13

We have expressed the recombinant reverse transcriptase (RT) of bovine leukemia virus (BLV) in bacteria. The gene encoding the RT was designed to start at its 5' end next to the last codon of the mature viral protease, namely the amino terminus of the RT matches the last 26 codons of the pro gene and is coded for by the pro reading frame. The RT sequence extends into the pol gene, utilizing the pol reading frame after overcoming the stop codon by adding an extra nucleotide (thus imitating the naturally occurring frameshift event). Hence we have generated a transframe polypeptide that is a 584-residues-long protein (see Rice, Stephens, Burny, and Gilden (1985) Virology 142, 357-377). This protein was partially purified after adding a six-histidine tag and studied biochemically testing a variety of parameters. The enzyme exhibits all activities typical of RTs, i.e., both RNA- and DNA-dependent DNA polymerase as well as a ribonuclease H (RNase H) activity. Unlike most RTs, the BLV RT is enzymatically active as a monomer even after binding a DNA substrate. The enzyme shows a preference for Mg2+ over Mn2+ in both its DNA polymerase and RNase H activities. BLV RT is relatively resistant to nucleoside triphosphate analogues, which are known to be potent inhibitors of other RTs such as that of HIV.
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PMID:Catalytic features of the recombinant reverse transcriptase of bovine leukemia virus expressed in bacteria. 1036 2

We have recently expressed in bacteria the enzymatically active reverse transcriptase (RT) of bovine leukemia virus (BLV) [Perach, M. & Hizi, A. (1999) Virology 259, 176-189]. In the present study, we have studied in vitro two features of the DNA polymerase activity of BLV RT, the processivity of DNA synthesis and the fidelity of DNA synthesis. These properties were compared with those of the well-studied RTs of human immunodeficiency virus type 1 (HIV-1) and murine leukaemia virus (MLV). Both the elongation of the DNA template and the processivity of DNA synthesis exhibited by BLV RT are impaired relative to the other two RTs studied. Two parameters of fidelity were studied, the capacity to incorporate incorrect nucleotides at the 3' end of the nascent DNA strand and the ability to extend these 3' end mispairs. BLV RT shows a fidelity of misinsertion higher than that of HIV-1 RT and lower than that of MLV RT. The pattern of mispair elongation by BLV RT suggests that the in vitro error proneness of BLV RT is closer to that of HIV-1 RT. These fidelity properties are discussed in the context of the various retroviral RTs studied so far.
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PMID:The processivity and fidelity of DNA synthesis exhibited by the reverse transcriptase of bovine leukemia virus. 1184 87


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