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)

Immunoprecipitation of labeled extracts from murine leukemia virus-infected cells with antisera specific for internal structural (gag) proteins yields three major gag-related polyproteins with molecular weights of 180,000 (Pr180gag-pol), 80,000, and 65,000 (Pr65gag). It has been shown by others that Pr65gag is the immediate precursor of the internal structural (gag) protein, and that Pr180gag-pol is the precursor to reverse transcriptase. In studies reported here, the 80,000-dalton gag-related polyprotein from Moloney strain murine leukemia virus (M-MuLV)-infected cells was found to be glycosylated by the following criteria: (i) incorporation of [3H]mannose, (ii) a change in electrophoretic mobility upon digestion with endoglycosidase H, and (iii) a change in electrophoretic mobility when glycosylation was inhibited by treatment of the cells with tunicamycin during labeling. The 80,000-dalton gag polyprotein has therefore been designated GpP80gag. The unglycosylated form of GpP80gag was a polypeptide of 75,000 daltons. A comparison of [3H]mannose and [3H]galactose labeling experiments suggested that GpP80gag is further glycosylated to yield a glycopolypeptide of 95,000 daltons. This 95,000-dalton polypeptide is relatively rapidly cleaved to yield two glycopeptides of 55,000 and 40,000 daltons which are released into the cell culture fluid, as soluble proteins. Cell-free translation of M-MuLV genomic RNA resulted in two major gag-related products of 75,000 and 65,000 daltons. The 65,000-dalton gag-related cell-free translation product comigrated with Pr65gag, and the 75,000-dalton cell-free product comigrated with the unglycosylated form of GpP80gag. Both of the gag-related cell-free translation products could be labeled with [35S]formyl methionine, which is incorporated only as the N-terminal amino acid during translation. Other investigators have shown that GpP80gag and Pr65gag differ at their N-termini, and these results combined with those reported here suggest that GpP80gag and Pr65gag are translated from two separate initiation sites in M-MuLV RNA.
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PMID:gag-Related polyproteins of Moloney murine leukemia virus: evidence for independent synthesis of glycosylated and unglycosylated forms. 46 93

High-level expression of a transpositionally competent Ty1 element fused to the inducible GAL1 promoter on a 2 microns plasmid (pGTy1) overcomes transpositional dormancy in Saccharomyces cerevisiae. To investigate the mechanisms controlling the rate of Ty1 retrotransposition, we quantitated transposition and Ty1 gene products in cells induced and uninduced for expression of pGTy1. The increase in Ty1 transposition was 45- to 125-fold greater than the increase in Ty1 RNA effected by pGTy1 induction. Translational efficiency of Ty1 RNA was not altered in transposition-induced cells, since p190TYA1-TYB1 protein synthesis increased in proportion to steady-state Ty1 RNA levels. Therefore, expression of a pGTy1 element increases the efficiency of Ty1 transposition at a posttranslational level. Galactose induction of pGTy1 enhanced TYA1 protein processing and allowed detection of processed TYB1 proteins, which are normally present at very low levels in uninduced cells. When the ability of genomic Ty1 elements to complement defined mutations in HIS3-marked pGTy1 elements was examined, mutations in the protease domain or certain mutations in the integrase domain failed to be complemented, but mutations in the reverse transcriptase domain were partially complemented by genomic Ty1 elements. Therefore, the activity of Ty1 elements in yeast cells may be limited by the availability of Ty1 protease and possibly integrase. These results suggest that Ty1 transposition is regulated at the level of protein processing and that this regulation is overcome by expression of a pGTy1 element.
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PMID:Posttranslational control of Ty1 retrotransposition occurs at the level of protein processing. 131 8

Strains carrying a marked Ty element (TyUra) in the LYS2 locus were transformed with plasmids bearing a differently marked Ty1 element (Ty1Neo) under the control of the GAL promoter. When these strains were grown in glucose, a low level of gene conversion events involving TyUra was detected. Upon growth on galactose an increase in the rate of gene conversion was seen. This homologous recombination is not the consequence of increased levels of transposition. When an intron-containing fragment was inserted into Ty1Neo, some of the convertants had the intron removed, implying an RNA intermediate. Mutations that affect reverse transcriptase or reverse transcription of Ty1Neo greatly reduce the induction of recombination in galactose. Thus, Ty cDNA is involved in homologous gene conversion with chromosomal copies of Ty elements. Our results have implications about the way families of repeated sequences retain homogeneity throughout evolution.
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PMID:Involvement of cDNA in homologous recombination between Ty elements in Saccharomyces cerevisiae. 137 87

Phosphate derivatives of AZT esterified with a carbohydrate (D-glucose, D-mannose, and ethyl D-mannopyranoside) and a hexadecyl chain were prepared from glucose 6-phosphate and D-mannose precursors. The 31P NMR study of the mannosyl phosphotriester series in the presence of large unilamellar vesicles demonstrated either an interaction with the external lipid layer or a transmembrane transport into the intravesicular interface. The antiviral activity, measured by the inhibition of cytopathogenicity on different infected cells and of reverse transcriptase activity in the supernatant of cultures, appeared to be comparable to that of AZT, in the micromolar range.
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PMID:Lipophilic glycosyl phosphotriester derivatives of AZT: synthesis, NMR transmembrane transport study, and antiviral activity. 171 47

Two novel enzyme-linked immunoassays (ELISA) for the quantitation of human immunodeficiency virus type 1 (HIV-1) coded glycoprotein with an Mr 120 (gp120) are described. These are based on the highly specific interaction between gp120 and the mannose-specific lectins from Narcissus pseudonarcissus (NPL) and Galanthus nivalis (GNL). Two systems were developed: (1) an HIV-protein ELISA using HIV-protein (also containing HIV-gp120) for the solid phase and NPL as a detector and (2) a lectin-ELISA using the NPL bound to the solid phase and GNL as detector. The HIV-protein ELISA was validated for quantitation of gp120 within the range 3 to 600 ng/ml; the lectin-ELISA for concentrations between 0.6 and 20000 ng gp120/ml. Serum components did not interfere with the binding of gp120 to the lectins. The ELISAs were used for the quantitation of gp120 in HIV-infected CEM cells in vitro. It was found that gp120 appeared in the medium earlier after infection than HIV-p24 and reverse transcriptase, suggesting that gp120 is released as free glycoprotein. Moreover, the ELISAs were also applied successfully for the detection of compounds that bind to gp120 and for the identification of antibodies directed against the highly pathogenic mannan portion of gp120. These ELISAs are considered to be suitable also for the detection of gp120 in the serum of HIV-infected individuals.
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PMID:Human immunodeficiency virus: novel enzyme-linked immunoassays for quantitation of envelope glycoprotein 120. 187 21

In this study we raised antibodies against Candida albicans mannans of serotype A and B which comprise mannose alpha(1----2)-and mannose alpha(1----3)-linked residues. These antibodies inhibited human immunodeficiency virus type IIIB (HIV-IIIB) infection of H9 cells in vitro; 5 micrograms/ml of antibodies against mannan from serotype A and 10 micrograms/ml of antibodies against serotype B mannan were sufficient to inhibit infection by almost 100 and 85%, respectively, after an incubation period of 4 days. During a prolonged incubation period (8-12 days), the amount of HIV particles (as measured by reverse transcriptase activity in the culture medium) increased again in assays with antibodies raised against serotype B, but only little in assays containing antibodies against serotype A. Applying the Western blotting technique and a novel enzyme-linked immunosorbent assay system it was established that the antibodies reacted with the gp120 of HIV-1 exclusively. Immunofluorescence inspection using a confocal laser scanning microscope revealed that the gp120 protein is exposed on the outer surface of H9 cells where it is recognized by the anti-mannan antibodies. These results indicate that mannan residues of C. albicans can serve as antigens to raise neutralizing antibodies against HIV infection.
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PMID:Antibodies against defined carbohydrate structures of Candida albicans protect H9 cells against infection with human immunodeficiency virus-1 in vitro. 205 8

We have found reverse transcriptase activity and virus-like particles only in yeast cells that contain a galactose-promoted Ty element induced on galactose. The cofractionation of reverse transcriptase, genomic-length Ty RNA, and a Ty-specified protein antigen in a particulate fraction and the ability of this complex to synthesize specifically a product that is homologous to the entire Ty suggest that reverse transcription of Ty RNA takes place in the particle. The absence of appreciable levels of reverse transcriptase and particles in uninduced cells despite the presence of at least 35 copies of chromosomal Ty elements suggest that some of these elements may be defective. The numerous virus-like particles visible in thin sections of Ty transposition-induced cells appear not to be infectious. These particles resemble the intracisternal A-type particles of the mouse and copia particles of Drosophila. The results support the idea that Ty elements and retroviruses share a common origin.
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PMID:Ty element transposition: reverse transcriptase and virus-like particles. 241 24

Treatment of Mo-MuLV-infected cells with cytochalasin B (CB), a microfilament disrupting drug, caused a reduction in virus yield as judged by infectivity assay and reverse transcriptase activity. Pulse-chase experiments with [3H]leucine showed that the env precursor, gPr80env, was inefficiently processed in cells treated with CB. In the presence of monensin, an inhibitor of glycoprotein transport, gPr80env accumulated intracellularly and no gp70 was observed on the cell surface, indicating a complete block in the processing of gPr80env. Pulse-chase studies also showed that gPr80env was not processed in the presence of monensin. SDS-PAGE analysis of TX-100-extracted cell cytoskeletons (TX-insoluble fraction) iodinated and immunoprecipitated with goat anti-gp70 antiserum showed that CB or monensin treatment caused a marked increase of gPr80env in the cytoskeleton-rich fraction. However, the amount of gPr80env associated with the TX-soluble fraction in both CB or monensin-treated and untreated cells labeled with [3H]leucine was about the same. The gPr80env in the TX-100-soluble fraction of the cell was the endoglycosidase H (Endo-H) sensitive mannose-rich form, whereas the cytoskeleton-associated gPr80env was the partially Endo-H-resistant complex carbohydrate form. In the presence of CB or monensin, the complex carbohydrate form of gPr80env accumulated in the cytoskeleton-rich cell fraction. Examination of Mo-MuLV ts1 mutant, which is defective in the processing of env precursor polyprotein, also revealed an accumulation of the complex carbohydrate form of gPr80env in the cytoskeleton-rich fraction and an absence of gp70 on the surface of the cell at the restrictive temperature (39 degrees C). These studies suggest that the cytoskeleton plays a role in the transport and processing of MuLV gPr80env and that oligosaccharide conversion is an important factor in this process. Further, the accumulation of gPr80env on the cytoskeleton of ts1 infected cells at restrictive temperature may play a role in the neurological disorder caused by Mo-MuLV ts1 mutant.
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PMID:Role of cell cytoskeleton in Mo-MuLV env transport and processing: implications in ts1 neuropathology. 243 68

A new reverse transcriptase (RT) inhibitor was extracted and purified from the red alga Schizymenia pacifica. The chromatographic behavior and chemical properties of this sea algal extract (SAE) suggest that it is a sulfated polysaccharide having a molecular weight of approximately 2,000,000. SAE is composed of galactose (73%), sulfonate (20%), and 3,6-anhydrogalactose (0.65%). SAE is a member of the lambda-carrageenan family, based on its infrared spectrum and products of hydrolysis. SAE selectively inhibited human immunodeficiency virus (HIV) RT and replication in vitro. When MT-4 cells were treated with more than 10(4) inhibitory units (IU) of SAE per ml after HIV infection, significant inhibition of viral antigen synthesis was observed. Furthermore, more than 90% of cells were viable in the cultures exposed to 4 X 10(4) to 8 X 10(4) IU of SAE per ml, while almost all the MT-4 cells in the control culture had died by 10 days after HIV infection. The inhibitory effect of SAE on HIV replication was confirmed by plaque reduction assays. The 50% inhibitory dose of SAE was 9.5 x 10(3) IU/ml. Chondroitin sulfate A, dermatan sulfate, heparan sulfate, keratan polysulfate, and heparin also inhibited the RT of avian myeloblastosis virus. SAE immediately inhibited RT activity when added to an assay mixture after the start of the reaction.
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PMID:Purification and characterization of an avian myeloblastosis and human immunodeficiency virus reverse transcriptase inhibitor, sulfated polysaccharides extracted from sea algae. 244 20

The glycosylation inhibitors 2-deoxy-D-glucose (2-dGlc) and, to a lesser extent, beta-hydroxynorvaline blocked the formation of syncytia in HIV (LAV/HTLV-III)-infected cells. Using monospecific polyclonal antibodies against recombinant envelope proteins gp110 and gp41 or monoclonal antibodies against env gp110, we could demonstrate a marked reduction in the immunoreactivity of these antigens in HIV-infected cells exposed to the glycosylation inhibitors. There was concomitant accumulation of core proteins p15 and p24, as shown by a solid phase radio-immunoassay, and a decreased oligosaccharide synthesis of env proteins, as monitored by the incorporation of [6-3H]GlcNAc. The reverse transcriptase was not affected by the compounds. Glycosylation inhibitors may be considered for the chemotherapy of AIDS or AIDS-related complex, or chemoprophylaxis of HIV-positive individuals.
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PMID:Glycosylation inhibitors block the expression of LAV/HTLV-III (HIV) glycoproteins. 309 81


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