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)

Polymerase chain reaction analysis was used to investigate the possible role of human spumaretrovirus and oncoretroviruses (human T-cell lymphotropic virus types I [HTLV-I] and II [HTLV-II]) in multiple sclerosis. Eleven patients with relapsing-remitting multiple sclerosis in exacerbation and 11 normal blood donors were included in the study. Cerebrospinal fluid cells, peripheral blood mononuclear cells, and plasma were cocultured with allogeneic mononuclear cells for 6 weeks. Cultured cells were subjected to polymerase chain reaction analysis with primers selected for the pol and gag (human spumaretrovirus), pol and env (HTLV-I), and pol (HTLV-II) genes. Polymerase chain reaction was negative in all patient and blood donor control samples, whereas positive controls were consistently reactive with high sensitivity. No culture exhibited cytopathic effects and supernatants were negative for reverse transcriptase activity. Thus, our results do not support a role for these retroviruses in the pathogenesis of multiple sclerosis.
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PMID:No evidence for spumavirus or oncovirus infection in relapsing-remitting multiple sclerosis. 133 76

Feline immunodeficiency virus (FIV) has morphological, physical and biochemical characteristics similar to human immunodeficiency virus (HIV), the cause of AIDS in man. However, it is antigenically and genetically distinct from HIV; an antigenic relatedness with equine infectious anaemia virus has been demonstrated. FIV has been molecularly cloned and sequenced. Diagnostic tests are commercially available and attempts at preparing inactivated, subunit and molecularly engineered vaccines are being made in different laboratories. During FIV infection a transient primary illness can be recognized, with fever, neutropenia and lymphadenopathy. After a long period of clinical normalcy a secondary stage is distinguished with signs of an immunodeficiency-like syndrome. The incubation period for this stage can be as long as 5 years, during which gradual impairment of immune function develops. Many FIV-infected cats are presented for the first time showing vague signs of illness: recurrent fevers, emaciation, lack of appetite, lymphadenopathy, anaemia, leucopenia and behavioural changes. Later, the predominant clinical signs observed are chronic stomatitis/gingivitis, enteritis, upper respiratory tract infections, and infections of the skin. Neoplasias, neurological, immunological and haematological disorder are seen in a smaller proportion. The immunodeficiency-like syndrome is progressive over a period of months to years. Concomitant infection with feline leukaemia virus has been shown to accelerate the progression of disease. In vitro, phenotypic mixing between FIV and an endogenous feline oncovirus (RD114) has been demonstrated which leads to a broadening of the cell spectrum of the lentivirus. Bovine immunodeficiency virus (BIV) has been isolated only once, and all attempts to obtain additional isolates have failed; it has been recovered from the leucocytes of cattle with persistent lymphocytosis, lymphadenopathy, lesions in the central nervous system, progressive weakness and emaciation. As with the feline representative, BIV also was found to possess a lentivirus morphology and to encode a reverse transcriptase with Mg++ preference; it replicates and induces syncytia in a variety of embryonic bovine tissues in vitro. Antigenic analyses have demonstrated a conservation of epitopes between the major core protein of BIV and HIV. The original isolate has been molecularly cloned and sequenced. Besides the three large open reading frames (ORFs) comprising the gag, pol, and env genes common to all replication-competent retroviruses, five additional small ORFs were found. Numerous point mutations and deletions were found, mostly in the env-encoding ORF. These data suggest that, within a single virus isolate, BIV displays extensive genomic variation.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Animal immunodeficiency viruses. 133 43

TED is a lepidopteran retrotransposon found inserted within the DNA genome of the Autographa californica nuclear polyhedrosis virus mutant, FP-D. To examine the proteins and functions encoded by this representative of the gypsy family of retrotransposons, the gag- and pol-like open reading frames (ORFs 1 and 2) were expressed in homologous lepidopteran cells by using recombinant baculovirus vectors. Expression of ORF 1 resulted in synthesis of an abundant TED-specific protein (Pr55gag) that assembled into viruslike particles with a diameter of 55 to 60 nm. Expression of ORF 2, requiring a -1 translational frameshift, resulted in synthesis of a protease that mediated cleavage of Pr55gag to generate p37, the major protein component of the resulting particles. Expression of ORF 2 also produced reverse transcriptase that associated with these particles. Both protease and reverse transcriptase activities mapped to domains within ORF 2 that contain sequence similarities with the corresponding functional domains of the pol gene of the vertebrate retroviruses. These results indicated that TED ORFs 1 and 2 functionally resemble the retrovirus gag and pol genes and demonstrated for the first time that an invertebrate member of the gypsy family of elements encodes active forms of the structural and enzymatic functions necessary for transposition via an RNA intermediate. TED integration within the baculovirus genome thus represents one of the first examples of transposon-mediated transfer of host-derived genes to an eukaryotic virus.
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PMID:The baculovirus-integrated retrotransposon TED encodes gag and pol proteins that assemble into viruslike particles with reverse transcriptase. 137 Nov 68

The pol I gene from HIV-1 encoding the protease, reverse transcriptase (RT) and endonuclease has been expressed in Escherichia coli. By modifying the fermentation conditions and developing a new purification scheme, the yield of purified RT has been increased substantially compared with that obtained in an earlier procedure. The expressed RT was purified to homogeneity by ammonium sulphate fractionation followed by chromatography on DEAE Sepharose, Heparin Sepharose, S Sepharose and Poly(A)-Sepharose. The purified HIV-RT is a heterodimer (p66/p51) with an isoelectric point close to 8 and with a tendency to aggregate. The proteolytic product (p51), corresponding to the N-terminal end of the RT molecule, was isolated and identified, as were also some bacterial polypeptides that co-elute with HIV-RT during the early stages of the purification. The heterodimer was crystallized in several morphological forms using the vapour-diffusion hanging drop technique. To concentrate the protein and to change the buffer for crystallization, reverse-salt-gradient chromatography and micropreparative columns were used. The best crystals diffracted to 9 A resolution. The best crystals of native RT diffracted to 9 A resolution and in complex with nucleic acids to 4.5 A resolution (using a rotating anode X-ray source).
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PMID:Purification, characterization and crystallization of recombinant HIV-1 reverse transcriptase. 137 51

We report here the isolation of Foret1, a repeated DNA sequence cloned from the fungal plant pathogen Fusarium oxysporum. This clone exhibits a high degree of sequence similarity with the retroviral pol genes. Sequences homologous to protease, reverse transcriptase, ribonuclease H are found in that order. The overall structure is homologous to the 'gypsy' class of LTR-retrotransposons. Its similarity to elements present in widely different organisms may result from its horizontal transmission in recent evolutionary time.
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PMID:Foret1, a reverse transcriptase-like sequence in the filamentous fungus Fusarium oxysporum. 138 Jun 91

The expression of the pol gene of human immunodeficiency virus type 1 occurs via a ribosomal frameshift between the gag and pol genes. The resulting protein, a Gag-Pol polyprotein, is produced at a level 5 to 10% of that of the Gag protein. The Gag-Pol polyprotein is incorporated into virions and provides viral protease, reverse transcriptase, and integrase, which are essential for infectivity. It is generally believed that the Gag-Pol polyprotein is incorporated into virions via interaction with the Gag protein, although the details of the mechanism are unknown. To further study this problem, we have constructed a human immunodeficiency virus type 1 proviral genome which overexpresses the Gag-Pol polyprotein (Pr160gag-pol). Transfection of this proviral genome (pGPpr-) into COS-1 cells resulted in the expression of full-length Pr160gag-pol polyprotein. Although the majority of the Pr160gag-pol was confined to the cells, low levels of reverse transcriptase activity were detectable in the cell supernatants. The cotransfection of pGPpr- with a second plasmid which expresses only the Pr55gag precursor (pGAG) resulted in a significantly higher level of Pr160gag-pol in the medium of transfected cells. Sedimentation analysis using sucrose density gradients demonstrated that most Pr160gag-pol was found in fractions corresponding to the density of virion particles, indicating that the Pr160gag-pol polyprotein was released in association with a Pr55gag viruslike particle. To further characterize the requirements for the release, a mutation was constructed to express an unmyristylated Pr160gag-pol polyprotein. Coexpression with Pr55gag demonstrated that the unmyristylated Pr160gag-pol was also incorporated into virion particles. Subcellular fractionation experiments revealed that the distributions of the Pr160gag-polmyr- and Pr160gag-pol in the membrane and cytosol were similar under low- or high-ionic-strength conditions. Taken together, these results suggest that myristylation of the Pr160gag-pol polyprotein is not required for the interaction with the Pr55gag necessary for packaging into a viruslike particle.
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PMID:The nonmyristylated Pr160gag-pol polyprotein of human immunodeficiency virus type 1 interacts with Pr55gag and is incorporated into viruslike particles. 138 61

5-Methylcytosine has been postulated to be an endogenous mutagen in procaryotes and eucaryotes leading to base substitution hot spots, C-->T transitions, resulting from spontaneous deamination of mC to T. The possibility remains, however, that a second mechanism involving mispairing of mC with A might also contribute to base substitution mutagenesis via G-->A transitions. Stimulation of the G-->A mutational pathway could involve preferential misincorporation of dAMP opposite template mC compared to C. To investigate this possibility, we synthesized a sequence containing mC at a defined template location. We compared the fidelity of copying mC versus C and the efficiency of extending mismatched base pairs at the mC position using three DNA polymerases, AMV reverse transcriptase, Drosophila DNA polymerase alpha, and mutant Escherichia coli Klenow fragment containing no proofreading exonuclease activity. Significant differences in misinsertion and mismatch extension efficiencies were observed only for the case of AMV reverse transcriptase. AMV reverse transcriptase was observed to incorporate dAMP 4 to 5-fold more efficiently opposite mC than C. Favored extension of a 5-MeC.A over C.A mispair was also observed with a difference of about 3-fold. In contrast to AMV reverse transcriptase, Klenow fragment showed no significant difference when copying either mC or C sites or when extending mispairs involving mC and C. Incorporation of dAMP opposite either C or mC was barely detectable using pol alpha, although pol alpha has been observed to form A.C mismatches in other sequences. While we cannot completely exclude the possibility that dAMP might be incorporated opposite mC in preference to C, our results suggest that contributions of the G-->A pathway to mC mutagenic hot spots are likely to be minor, lending additional support to the model invoking deamination of mC.
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PMID:A comparison of the fidelity of copying 5-methylcytosine and cytosine at a defined DNA template site. 138 39

Beside the risk of infection via HIV-1-contaminated blood, ophthalmologists are especially interested in the possibility of HIV-1 infection via tears. Therefore we tried to isolate HIV-1 from tears of 50 HIV-1-infected persons in different stages of disease by reverse transcriptase (RT) and by p24-antigen (p24-AG) in the cultures. Simultaneously we tried to isolate HIV-1 in the supernatant from peripheral blood lymphocytes (PBL), which was successful in 32 of the 50 examined specimens. HIV-1 could not be isolated from the tears of these persons. In addition, polymerasechain-reaction (PCR) was performed to detect proviral sequences (gag, pol, env) of HIV-1 in tears and blood of ten HIV-1-infected patients. While in all the examined patients gag, pol and env could be detected in the blood samples, only one tear sample was found positive for gag and pol DNA fragments. These results indicate that tears of HIV-1-positive contain extremely low quantities of tissue culture infectious doses (TCID) of HIV-1 in contrast to PBL. HIV-1 infection via tears therefore appears to be unlikely.
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PMID:Infrequent detection of HIV-1 components in tears compared to blood of HIV-1-infected persons. 138 31

Human immunodeficiency virus (HIV) has been implicated as the etiologic agent of acquired immunodeficiency syndrome and is a member of the sub-family Lentivirinae within the family Retroviridae. HIV type 1 (HIV-1) contains three major genes, gag, pol and env, which code for (1) core proteins, (2) a protease, reverse transcriptase and integrase, and (3) envelope glycoproteins, respectively. The core proteins p17, p24 and p15 are derived from gag precursor, p55, by endoproteolytic cleavage. The two nucleic-acid-binding proteins p7 and p9 are synthesized from p15 by proteolytic cleavage. These two structural proteins are apparently needed for the ribonucleoprotein-core formation. The envelope glycoproteins gp120 and gp41 (gp120-gp41 complex) are also generated by cleavage env precursors, gp160. The assembly of HIV-1 particles, like other retroviruses, appears to involve the association of the env precursor gp160 with the gag proteins. There are several factors which influence the assembly and budding process of HIV-1. In this article, we describe important events in HIV-1 morphogenesis and factors which influence this aspect of the HIV-1 life cycle.
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PMID:Morphogenesis of human immunodeficiency virus type 1. 138 14

1. A 220 bp DNA fragment was obtained from three different species of salmonids during PCR analysis using a primer sequence based on human beta-2 microglobulin. All of the 220 bp fragments showed strong homology to each other. 2. Several of the DNA sequences also contained protein reading frames. Searching DNA and protein databases revealed significant homology to a segment of the pol gene (reverse transcriptase) from various retroviruses. Phylogenetic analysis at both the DNA and the protein levels showed clustering of the fish sequences and the closest viral sequence was the Moloney murine leukaemia virus (MoMuLV). Southern analysis indicated that there are several copies of the gene dispersed throughout the salmonid genome. 3. Preliminary results suggest that these sequences may be unique to the family Salmonidae. This would suggest that this retrovirus was incorporated in the DNA of an ancestral salmonid prior to the evolution and divergence of this family of fish.
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PMID:Isolation of a putative retrovirus pol gene fragment from trout. 152 19


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