Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Production of infectious Mason-Pfizer monkey virus (M-PMV) was enhanced after treatment of the CMMT cell line with 2.5 x 10(-5) M dexamethasone phosphate (DXM). The reverse transcriptase (RT) activity and infectivity titers of treated culture fluids were enhanced by five- and tenfold, respectively. Along with stimulation of M-PMV synthesis, a simian type C virus (SCV) was also detected by electron microscopic and RT analyses. The SCV was serologically related to the endogenous baboon type C virus. 5-iododeoxyuridine (IUDR) also activated the SCV in the CMMT cell line while significantly inhibiting the production of infectious M-PMV. The activation of endogenous SCV by IUDR or DXM was transitory, since removal of these compounds from the growth medium resulted in the disappearance of SCV buds and the related RT activity; however, low levels of specific viral structural proteins continued to be synthesized intracellularly. Similarly, the enhancement of M-PMV production seen with DXM was lost when the treated cells were subcultured for 2 weeks in the absence of the hormone.
 ...
PMID:Expression of Mason-Pfizer and simian type C viruses in the presence of 5-iododeoxyuridine and dexamethasone. 6 14

The reverse transcriptase of Mason-Pfizer monkey virus (M-PMV) has been isolated and partially purified by ion exchange chromatography. Sera from rabbits immunized with the partially purified enzyme have been shown by microimmunodiffusion analysis to be immunologically specific for the M-PMV polymerase. The immune serum also specifically inhibits M-PMV polymerase activity and this inhibitory activity has been shown to reside in the IgG fraction of the serum. The application of these reagents to examining virus identity and investigating the possible viral aetiology of human breast cancer is discussed.
 ...
PMID:Production of antiserum to the reverse transcriptase of Mason-Pfizer monkey virus. 7 May 6

A method for the study of oncovirus envelope antigens was developed, bases on the precipitation of intact virions by a double antibody technique. The amount of precipitated virus was then measured as reverse transcriptase activity. The method was designated the virion precipitation test (VPT). It has been used for titration of antibodies to envelope antigens of oncoviruses. The study of envelop antigens of 11 different oncoviruses permitted their differentiation into the following groups: (1) murine type-C viruses: (2) feline type-C viruses; (3) simian type-C viruses; (4) the RD-114/BEV group; (5) Mason-Pfizer monkey virus (M-PMV); (6) bovine leukemia virus; (7) avian type-C viruses; (8) mouse mammary tumor virus. No common antigenic determinants were detected in the last three groups. Mammalian type-C viruses (RD-114, NIH-MuLV, G-MuLV) had common antigenic determinants in the envelope, as demonstrated with an anti-RD-114 serum. Mammalian type-C viruses also shared antigenic determinants with M-PMV. The relationship of type-C viruses to M-PMV decreased in the following order: RD-114--NIH-MuLV--G-MuLV. It was also shown that the endogenous xenotropic feline RD-114 virus was more closely related to xenotropic NIH-MuLV than to ecotropic G-MuLV. The nature of the common antigenic determinants, as demonstrated by VPT on the surface of mammalian type-C viruses and M-PMV, and their significance for the concept of oncovirus evolution are discussed.
 ...
PMID:A new virion precipitation test for oncovirus envelope antigens which detects common antigenic determinants in mammalian type-C viruses and Mason-Pfizer monkey virus. 8 21

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

Chromosomal DNA was isolated from CMMT cells which were producing Mason-Pfizer monkey virus (M-PMV), a type D simian retrovirus. Human embryonic cells were transfected with the DNA. About 2 weeks after transfection, 3 of 7 culture dishes began to produce M-PMV which could be detected by virus-mediated cell fusion in RSb human cells dually transformed by Rous sarcoma virus and simian virus 40, reverse transcriptase assay, and electron microscopy. Mock-transfected cultures did not produce virus.
 ...
PMID:Transfection with the proviral DNA of a type D retrovirus (Mason-Pfizer monkey virus). 681 99

Amplification of avian paramyxovirus serotype 1 (APMV-1)-specific nucleic acid fragments, followed by restriction endonuclease analysis (REA) using BglI, was carried out to type strains according to their virulence. Primer sequences were used to amplify a 202 base pair fragment, encompassing the fusion protein cleavage site, in a one-step reverse transcriptase-polymerase chain reaction (RT-PCR) test for detection of a range of field cases and reference strains of APMV-1. Subsequent REA of the amplified fragments enabled differentiation of low virulent lentogenic field and vaccine strains from more virulent mesogenic and velogenic field strains of APMV-1, including pigeon PMV-1. In the present paper, we report the development and application of a one-step RT-PCR test coupled with REA as a fast, specific method for both the detection and typing of APMV-1 from field samples.
 ...
PMID:Detection and differentiation of pathogenicity of avian paramyxovirus serotype 1 from field cases using one-step reverse transcriptase-polymerase chain reaction. 1242 43

All retroviruses contain two copies of genomic RNA that are linked noncovalently. The dimeric RNA of human immunodeficiency virus type 1 (HIV-1) undergoes rearrangement during virion maturation, whereby the dimeric RNA genome assumes a more stable conformation. Previously, we have shown that the packaging of the HIV-1 polymerase (Pol) proteins reverse transcriptase (RT) and integrase (IN) is essential for the generation of the mature RNA dimer conformation. Analysis of HIV-1 mutants that are defective in processing of Pol showed that these mutant virions contained altered dimeric RNA conformation, indicating that the mature RNA dimer conformation in HIV-1 requires the correct proteolytic processing of Pol. The HIV-1 Pol proteins are multimeric in their mature enzymatically active forms; RT forms a heterodimer, and IN appears to form a homotetramer. Using RT and IN multimerization defective mutants, we have found that dimeric RNA from these mutant virions has the same stability and conformation as wild-type RNA dimers, showing that the mature enzymatically active RT and IN proteins are dispensable for the generation of mature RNA dimer conformation. This also indicated that formation of the mature RNA dimer structure occurs prior to RT or IN maturation. We have also investigated the requirement of Pol for RNA dimerization in both Mason-Pfizer monkey virus (M-PMV) and Moloney murine leukemia virus (MoMuLV) and found that in contrast to HIV-1, Pol is dispensable for RNA dimer maturation in M-PMV and MoMuLV, demonstrating that the requirement of Pol in retroviral RNA dimer maturation is not conserved among all retroviruses.
 ...
PMID:Analysis of the contribution of reverse transcriptase and integrase proteins to retroviral RNA dimer conformation. 1585 17

Retroviral proteases (PRs) cleave the viral polyprotein precursors into functional mature proteins late during particle release and are essential for viral replication. Unlike most retroviruses, beta-retroviruses, including Mason-Pfizer monkey virus (M-PMV), assemble immature capsids within the cytoplasm of the cell. The activation of beta-retroviral proteases must be highly regulated, because processing of the Gag-related polyprotein precursors occurs only after transport of immature capsids to the plasma membrane and budding. Several beta-retroviral proteases have unique C-terminal extension sequences, containing a glycine-rich motif (G-patch), which specifically binds in vitro to single-stranded nucleic acids. In M-PMV PR the G-patch is removed in vitro as well as in vivo by autoproteolytic processing to yield truncated active forms of PR. To investigate the role of the G-patch domain on the virus life cycle, we introduced mutations within the C-terminal domain of protease. We found that the G-patch domain of M-PMV PR is not required for the processing of viral polyproteins, but it significantly influences the infectivity of M-PMV, the activity of reverse transcriptase, and assembly of immature capsid within the cells. These results demonstrate for the first time that the G-patch domain of M-PMV PR is critical for the life cycle of beta-retroviruses, and its evolutionary conservation within members of this genus suggests its importance for retroviruses that display D-type morphology.
 ...
PMID:The RNA binding G-patch domain in retroviral protease is important for infectivity and D-type morphogenesis of Mason-Pfizer monkey virus. 1625 73

To improve our understanding of myxomatous degeneration of the valvar tissue as seen in mitral valve prolapse, we have compared the biosynthetic phenotype of the connective tissue cells in myxomatous segments (n=4) resected during surgery with that of homologous segments of normal valves (n=4) harvested in age-matched organ donors. The steady-state level of mRNA for selected extracellular matrix macromolecules and metalloproteinases was assessed by quantitative (internal standard controlled) reverse transcriptase-polymerase chain reaction (RT-PCR). Among the investigated gene products, the decorin mRNA expression was significantly increased in degenerative valve compared with normal tissue (211+/-48 vs. 100+/-70, p<0.02). The level of fibrillin 2 also tended to be increased (194+/-88 vs. 100+/-81, p=0.08). These results suggest that myxomatous valvar tissue is characterized by an overexpression of mRNA for decorin. Owing to the role of this small leucine-rich proteoglycan in the regulation of fibril assembly and stability, this alteration may account for or is a result of a defective organization of the collagen and elastic fibers in this disease and contribute to the intrinsic distensibility and fragility of the myxomatous tissue.
 ...
PMID:Increased mRNA expression of decorin in the prolapsing posterior leaflet of the mitral valve. 1767 80

The morphogenesis of retroviral particles is driven by Gag and GagPol proteins that provide the major structural component and enzymatic activities required for particle assembly and maturation. In addition, a number of cellular proteins are found in retrovirus particles; some of these are important for viral replication, but many lack a known functional role. One such protein is clathrin, which is assumed to be passively incorporated into virions due to its abundance at the plasma membrane. We found that clathrin is not only exceptionally abundant in highly purified HIV-1 particles but is recruited with high specificity. In particular, the HIV-1 Pol protein was absolutely required for clathrin incorporation and point mutations in reverse transcriptase or integrase domains of Pol could abolish incorporation. Clathrin was also specifically incorporated into other retrovirus particles, including members of the lentivirus (simian immunodeficiency virus, SIVmac), gammaretrovirus (murine leukemia virus, MLV) and betaretrovirus (Mason-Pfizer monkey virus, M-PMV) genera. However, unlike HIV-1, these other retroviruses recruited clathrin primarily using peptide motifs in their respective Gag proteins that mimicked motifs found in cellular clathrin adaptors. Perturbation of clathrin incorporation into these retroviruses, via mutagenesis of viral proteins, siRNA based clathrin depletion or adaptor protein (AP180) induced clathrin sequestration, had a range of effects on the accuracy of particle morphogenesis. These effects varied according to which retrovirus was examined, and included Gag and/or Pol protein destabilization, inhibition of particle assembly and reduction in virion infectivity. For each retrovirus examined, clathrin incorporation appeared to be important for optimal replication. These data indicate that a number of retroviruses employ clathrin to facilitate the accurate morphogenesis of infectious particles. We propose a model in which clathrin contributes to the spatial organization of Gag and Pol proteins, and thereby regulates proteolytic processing of virion components during particle assembly.
 ...
PMID:Clathrin facilitates the morphogenesis of retrovirus particles. 2173 76


1 2 Next >>