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

---

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

Sixteen isolates of simian retrovirus closely related to human immunodeficiency virus (HIV) were obtained from healthy African green monkeys (AGM) (Cercopithecus aethiops). The first isolate was obtained from a monkey seropositive for HIV, and the others were isolated from monkeys harboring antibodies to the first isolate. These simian retroviruses were referred to as simian immunodeficiency virus from AGM, SIV[AGM], due to their cross-reactivities with HIV structural proteins. These SIV[AGM] isolates were found by Western blotting analysis to have virus-specific proteins of 120, 66, 55, 32-40, 24 and 17 kDa, which were all similar in size to the analogous proteins of HIV. Putative gag proteins of p55, p24 and p17 were recognized by sera of human AIDS patients, but the corresponding env proteins of 32-40 and 120 kDa showed only weak cross-reactivity with those of HIV. The transmembrane glycoproteins of these 3 SIV[AGM] isolates showed size heterogeneity, being 32, 35 and 40 kDa. This virus had particles that were morphologically similar to those of HIV, and had Mg2+-dependent reverse transcriptase. Furthermore, the SIV[AGM] showed tropism and cytopathic effects on CD4-positive human cell lines. In a sero-epidemiological survey of SIV[AGM] in various non-human primates, 2 other African monkey species, the mandrill and de Brazza's monkey, were also found to have antibodies to SIV[AGM]. These HIV-related simian retroviruses will be important in determining the origin and transmission of HIV group viruses, and may provide useful animal models for studies on the infection and pathogenesis of HIV and AIDS.
...
PMID:Isolation of simian immunodeficiency virus from African green monkeys and seroepidemiologic survey of the virus in various non-human primates. 244 23

We have determined the nucleotide sequence of the Drosophila retrotransposon 1731. 1731 is 4648 bp long and is flanked by 336 bp terminal repeats (LTRs) previously described as being reminiscent of provirus LTRs. The 1731 genome consists of two long open reading frames (ORFs 1 and 2) which slightly overlap each other. The ORF 1 and 2 present similarities with retroviral gag and pol genes respectively as shown by computer analysis. The pol gene exhibits several enzymatic activities in the following order: protease, endonuclease and reverse transcriptase. It is possible that 1731 also encompasses a ribonuclease H activity located between the endonuclease and reverse transcriptase domains. Moreover, comparison of the 1731 pol gene with the pol region of copia shows similarities extending over the protease, endonuclease and reverse transcriptase domains. We show that codon usage in the two retrotransposons is different. Finally, no ORF able to encode an env gene is detected in 1731.
...
PMID:Primary structure and functional organization of Drosophila 1731 retrotransposon. 245 22

An amphotropic retrovirus packaging cell line was constructed in which the gag, pol, and env genes of the helper virus are separated on two different plasmids and in which the packaging signals and 3' long terminal repeats are removed. To do this, a plasmid containing the Moloney murine leukemia virus gag and pol gene was transfected into NIH 3T3 cells, and a plasmid containing the 4070A amphotropic env gene was transfected into one of the resulting clones which produced a high level of reverse transcriptase. A clone producing a high level of amphotropic env protein (GP + envAm12) was then isolated. When transfected into GP + envAm12 cells, titers of the retroviral vector N2, containing a neomycin resistance gene, ranged from 10(2) to greater than 10(6) CFU/ml on 3T3 cells, from 1.3 x 10(4) to 2.7 x 10(5) CFU/ml on HeLa cells, and from 1.0 x 10(2) to 6.0 x 10(3) CFU/ml on K562 cells when assayed by G418 resistance. These titers were comparable to titers obtained using the PA317 cell line. Tests for the safety of the GP + envAm12 packaging line showed no evidence for the generation of wild-type virus. Thus, the efficiency and safety of the GP + envAm12 cell line in gene transfer into human cells may provide an optimal system for experiments whose goal is human gene therapy.
...
PMID:Construction and use of a safe and efficient amphotropic packaging cell line. 246 7

Molecular evolution and phylogeny of different human immunodeficiency virus type 1 (HIV1) strains, of a type 2 (HIV2) strain, and of two simian immunodeficiency viruses (SIVAGM and SIVMAC) have been studied by comparing the nucleotide sequences of the two regions of their pol genes which encode the reverse transcriptase (RT) and endonuclease/integrase (EN). The analyses show that the different HIV 1s form one cluster (HIV1 group) and that the SIVs and HIV2 form another (HIV2 group). When the entire genomes of a HIV1, a HIV2, and the two SIVs were compared, the SIVAGM showed a unique pattern of mutation accumulations; that is, the SIVAGM has accumulated more nonsynonymous changes than synonymous changes in the RT and EN regions after its recent divergence from SIVMAC-142, and, furthermore, it has a deletion of approximately 350 bp in the region between the pol and env genes. The SIVAGM was apparently derived from cell cultures infected with a macaque isolate, SIVMAC-251. The contamination provides an opportunity to measure the maximum rate of evolution in the SIVAGM by comparing its DNA sequence to those of SIVMAC-251 and SIVMAC-142. The analysis shows that the rates are given approximately by (1.95 +/- 1.37) x 10(-3)/site/year for one SIVAGM sequence and (5.18 +/- 2.25) x 10(-3)/site/year for another.
...
PMID:Molecular evolution of the human and simian immunodeficiency viruses. 246 34

Infectious retrovirus particles consist of a core structure containing RNA and gag-pol polypeptides surrounded by a lipid membrane studded with env proteins. A recombinant vaccinia virus was designed to express the entire gag-pol precursor protein of the human immunodeficiency virus type 1. Synthesis and processing of gag proteins occurred in mammalian cells infected with this live recombinant virus, and reverse transcriptase was detected largely in the medium. Electron micrographs revealed immature retrovirus-like particles budding from the plasma membrane and extracellular particles with morphological characteristics of immature and mature human immunodeficiency virus. The latter contained functional reverse transcriptase as well as processed p24 and p17 gag polypeptides. Thus, assembly and maturation of human immunodeficiency virus-like particles can occur in the absence of either infectious RNA molecules or env proteins. The production of noninfectious virus-like particles by expression vectors should be useful for biochemical studies and could provide a safe source of material for the development of vaccines.
...
PMID:Human immunodeficiency virus-like particles produced by a vaccinia virus expression vector. 247 31

In central equatorial Africa the frequency of uninterpretable or atypical Western blots (WB)--ie. antibodies to gag proteins only--can represent up to 50% of enzyme-linked immunosorbent assay (ELISA)-positive samples. To date the significance of such serology remains unknown. Nevertheless, an unusual HIV-1 strain has been isolated from the blood of a healthy Gabonese individual who presented an atypical WB. This virus, identified as isolated HIV-1OYl, grew to low titres of reverse transcriptase activity (less than 50,000 cpm/ml) and was not obviously cytopathic. Radioimmunoprecipitation and peptide ELISA studies indicated that the lack of env-specific reactivity was probably due to the absence of antibodies to the viral glycoproteins, rather than the virus encoding a highly divergent envelope protein. Molecular cloning and sequencing of the provirus proved it to be a string of HIV-1 which was genetically closer to European and North American than to African strains. Furthermore the envelope protein sequence contained all the features of a typical HIV-1 env gene. However, the tat gene derived from the proviral clone was functionally defective. Site-directed mutagenesis of this gene showed that this was due to the substitution of an essential cysteine residue for a serine. Polymerase chain reaction amplification of the tat gene, as well as parts of the gag and env gene sequences of HIV-1OYl, showed that essentially all of the proviruses were defective. These data emphasize the need to view HIV isolates as populations of distinct genomes capable of complementing each other.
...
PMID:A highly defective HIV-1 strain isolated from a healthy Gabonese individual presenting an atypical western blot. 255 49

Lymphoid cell lines derived from the peripheral blood of French West Indian patients with HTLV-I sero-positive Tropical Spastic Paraparesis and HTLV-I isolates were characterized. While patients' peripheral blood lymphocytes did not express detectable HTLV-I antigens when uncultured, they did so after short-term culture. Established cell lines were of T-cell lineage: CD2+, CD3+, CD4+, CD7+, WT31+ with activated T-cell markers CD25+, DR+ and a clonal rearrangement of the beta and gamma genes of the T-cell receptor. HTLV-I antigens were detected in cell lines by indirect immunofluorescence, Western blot and radio-immunoprecipitation assays. After 4 months in culture, low levels of Mg2+ dependent reverse transcriptase activity were detected and electron microscopy revealed numerous type-C retroviral particles similar to HTLV-I virions. Western blot and radio-immunoprecipitation analysis of purified viruses revealed gp46, p24, p19 and Pr53gag proteins similar to those detected in HUT 102 and MT2 cell lines. Deep analysis of env-coded precursor of one TSP versus ATL isolates revealed minor differences in their molecular weights. Southern blot analysis using 32P HTLV-I env gene as a probe showed the presence of HTLV-I proviral fragments clonally integrated into the genome of the cell lines. Our data suggest that HTLV-I isolated from Tropical Spastic Paraparesis does not differ significantly from the leukemogenic prototypes. Does HTLV-I induce either acute lymphoproliferative diseases or chronic neuromyelopathies depending upon as yet unknown co-factors? This question remains to be determined.
...
PMID:Characterization of HTLV-I isolates and T lymphoid cell lines derived from French West Indian patients with tropical spastic paraparesis. 256 21

We have used the polymerase chain reaction (PCR) to detect by co-amplification, multiple regions of the HIV-1 genome in infected cells. Genomic RNA and DNA from productively infected H9 cells were independently extracted and amplified in reactions with and without reverse transcriptase respectively using primer pairs to the gag, env, tat and nef regions of the viral genome in the same reaction mixture. PCR-products were analysed by liquid hybridization with end labelled oligonucleotide probes followed by gel-electrophoresis (oligomer hybridization). The primer pairs were capable of detecting as few as 10 copies of RNA and 10-20 copies of integrated proviral DNA. The ability to co-amplify multiple target regions in the same incubation mixture provides a method for detecting and confirming the presence of HIV-1 in samples for which limited nucleic acid is available. In addition, in reconstitution experiments, the same method was used to detect HIV-1 and HTLV-I simultaneously with comparable sensitivity (20-40 gene copies each). This offers the possibility of simultaneous diagnosis of multiple viral infections, such as those that occur in AIDS, on the same sample preparation.
...
PMID:Co-amplification of multiple regions of the HIV-1 genome by the polymerase chain reaction: potential use in multiple diagnosis. 257 Nov 15

A rapid, sensitive, and reproducible method for the isolation of human cell clones containing nonconditional, replication-defective (rd) mutants of Mason-Pfizer monkey virus (M-PMV), the prototype of the D-type retroviruses is described. The two mutants, rd1 and rd2, thus far isolated have been analyzed for virus particle production (using radiolabeled precursors and by electron microscopy) and for the status of intracellular viral precursors. Thin sections of rd1 and rd2 infected cells showed typical M-PMV particles when observed under electron microscope. A more direct assay of virus production, by labeling the mutant cell clones with [3H]uridine, also showed a distinct virus peak at an approximate density of 1.16 g/ml when culture fluids from rd1 and rd2 were analyzed. Analyses of these two mutants showed no defect in either gag or env gene products, however, further analysis of rd1 showed that the Pr180gag-pol was altered in its migration on SDS-polyacrylamide gel electrophoresis and no reverse transcriptase activity could be detected in rd1 virions. Mutant rd2, on the other hand, assembles noninfectious virus particles that are otherwise indistinguishable from those produced by wild-type cell clones. The biochemical basis for the defect in this mutant remains to be established.
...
PMID:A rapid screening procedure for the isolation of nonconditional replication mutants of Mason-Pfizer monkey virus: identification of a mutant defective in pol. 257 6

The transmembrane glycoprotein (gp41) of human immunodeficiency virus type-1 (HIV-1) has a long cytoplasmic domain of unknown functional significance. To investigate the role of the carboxy-terminal (C-terminal) portion of the HIV-1 envelope protein in viral replication, infectivity, and cytopathogenicity, we examined the properties of a panel of mutants with variable deletions in the 3'-env region. Deletion of the C-terminal 76 amino acids did not abolish production of reverse transcriptase upon transfection of COS-1 cells. Deletion of the C-terminal 6-14 amino acids appeared sufficient to alter the replication pattern, infectivity, and cytopathogenicity of some clones. The data suggest that conformational determinants or specific sequences are responsible for the observed changes, rather than simply the length of the gp41 cytoplasmic tail.
...
PMID:Role of the carboxy-terminal portion of the HIV-1 transmembrane protein in viral transmission and cytopathogenicity. 278 44


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---