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)

The expression and biological function of interleukin-6(IL-6), and its receptor mRNA, were studied in a human megakaryocytic cell line (CMK). IL-6 possessed stimulatory effects on the DNA synthesis as well as colony formation of CMK cells. The IL-6 receptor mRNA could be detected by the method of reverse transcriptase polymerase chain reaction (RT-PCR) but not Northern blotting. On the contrary, IL-6 mRNA was detected by the method of RT-PCR, and its expression induced by the addition of 12-O-tetradecanoylphorbol-13-acetate (TPA) could be clearly shown by Northern blotting. These findings indicate that IL-6 and its receptor mRNA should be analyzed by both methods, and the growth and differentiation of CMK cells may be controlled by an IL-6 autocrine loop. Next, the expression and biological role of low molecular GTP-binding proteins (smg p21A and -B) mRNAs were examined in CMK cells. Both the smg p21A and -B mRNAs were detected in CMK cells using Northern blotting, and their levels were markedly elevated by TPA treatment. The mRNA level of glycoprotein IIb, a typical marker of the megakaryocytes, was increased by TPA, but the time course of the increase in the smg p21 mRNA levels was more rapid that that in the GPIIb mRNA level. These findings suggest that smg p21s play an important role during the TPA-induced differentiation of CMK cells.
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PMID:[Expression and detection of platelet specific genes in human megakaryocytic cells]. 177 68

The chronically infected promonocytic clone U1 expresses low-to-undetectable constitutive levels of human immunodeficiency virus (HIV). Virus replication in these cells can be increased up to 25-fold by phorbol esters (phorbol-12-myristate-13-acetate), recombinant cytokines such as tumor necrosis factor-alpha, and cytokine-enriched mononuclear cell supernatants. We have tested specific activators of protein kinases (PK) and PK inhibitors (isoquinolinesulfonamide derivatives), as well as calcium-mobilizing agents, for their effect on constitutive and induced virus expression in U1 cells. Virus expression was measured by reverse transcriptase, Western blot, and nuclear run-on analysis. Activation of PKC by 1-oleyl,2-acetylglycerol, a synthetic analog of the natural ligand 1,2-diacylglycerol, and bryostatin 1 (a recently described specific PKC activator) resulted in a two- to eightfold increase in virus production. In contrast, activators of cyclic-nucleotide-dependent PKs were not effective in inducing virus expression. PK inhibitors were tested for their effect on HIV upregulation by cytokines and other inducing agents. The isoquinolinesulfonamide derivative H7, a potent inhibitor of PKC activation, effectively blocked (70 to 90%) HIV induction by cytokines and phorbol-12-myristate-13-acetate. The derivative HA1004, which is more selective for cyclic-nucleotide-dependent kinases, did not suppress viral induction. In addition, increases in intracellular calcium levels dramatically enhanced HIV production induced by both specific PKC activators and cytokines. These results indicate that activation of PKC is a common pathway involved in the upregulation of HIV expression in chronically infected cells stimulated by cytokines and other inducing agents.
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PMID:Direct and cytokine-mediated activation of protein kinase C induces human immunodeficiency virus expression in chronically infected promonocytic cells. 220 Aug 85

Since the first controlled clinical trial of zidovudine (ACT) was terminated in the fall of 1986, much has been learned concerning the use of this agent in the treatment of human immunodeficiency virus (HIV) infection. The recent report of HIV resistance associated with long-term AZT therapy has accelerated the sense of urgency about the development of additional agents for use--either alone or in combination with AZT--against this infection. Several new agents are in various stages of preclinical or clinical evaluation. Some, such as dideoxycytidine, dideoxyinosine, dideoxydidehydrothymidine, azidouridine, and foscarnet, inhibit viral DNA synthesis through inhibition of reverse transcriptase. Other potentially useful agents presumably act at different stages of infection. Soluble CD4, for example, is a soluble form of the receptor to which HIV must bind to infect cells, and castanospermine represents a new class of compounds that block the maturation process of the viral glycoprotein. An apparently more potent and less toxic analogue of the latter agent, N-butyl-deoxynojirimycin, is currently in phase I testing.
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PMID:New antiretroviral agents in the clinic. 223 36

Chemical agents including 5-iodo-2'-deoxyuridine (IUdR), 4-O-methyl 12-O-tetradecanoyl phorbol-13-acetate (TPA), phorbol, and the tumor promoters teleocidin and TPA were tested for their ability to induce Human T-cell leukemia-lymphoma virus Type I (HTLV-I) expression in the low-virus producer MT-1 cell line and in the non-virus producer C63/CRII-2 cell line, which contains at least one integrated HTLV-I genome equivalent per cell [26]. Viral antigen expression increased from 0.3% to 8.7% in the MT-1 cell line after treatment with IUdR, while TPA and teleocidin were marginally or non-effective as inducers. Chemicals did not induce HTLV-I antigen expression in the C63/CI(II-2) cell line. No enhancement of reverse transcriptase activity or alteration of proviral organization was observed after chemical treatment of MT-1 cells.
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PMID:The effects of tumor promoters on HTLV-1 expression in a low-virus producer and a non-virus producer cell line. 245 10

Macrophages were harvested from the peritoneal cavities of healthy specific-pathogen-free cats by saline lavage. Three days before collection, the peritoneal cavities were stimulated with glutaraldehyde-fixed Saccharomyces cerevisiae cells to induce greater numbers of macrophages and to begin the activation sequence. Peritoneal macrophages from cats stimulated once with yeast consisted mainly of small macrophages and a smaller number of larger activated macrophages. After several days in culture, many of the small macrophages became activated and a portion of the activated macrophages developed into multinucleated giant cells. Peritoneal cells from cats that were stimulated twice or three times with yeast at 3-week intervals consisted of a higher proportion of activated macrophages initially and produced more and larger multinuclear giant cells with time. Cultures of peritoneal cells stimulated once with yeast were easily infected in vitro with feline immunodeficiency virus (FIV) and produced a transient burst of reverse transcriptase activity. After the initial burst of virus replication, the infection became latent. Even more multinucleated giant cells appeared after infection, and many of these cells fused with each other. Replicating virus could be rescued from the latently infected macrophages after 2 to 3 weeks of phorbol myristate acetate stimulation and cocultivation with T-lymphocyte-enriched peripheral blood mononuclear cells. Multiply stimulated peritoneal cells, which contained a much higher proportion of activated macrophages, could also be infected in vitro with FIV. The infection usually became latent, however, without going through an initial replicative stage. Peritoneal cells from chronically FIV-infected specific-pathogen-free cats contained a higher proportion of activated macrophages and were latently infected with FIV from the outset.
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PMID:Infection of peritoneal macrophages in vitro and in vivo with feline immunodeficiency virus. 247 73

A rapidly proliferating T-cell line, HCD8, was derived from the peripheral blood lymphocytes of an apparently healthy individual during the course of a T-cell cloning experiment. This T-cell line expressed a very unusual phenotype: CD1+, CD2-, CD3+ (cytoplasmic), CD4-, CD5+, CD7+, CD8-, interleukin-2 receptor (IL-2 R) (p55)-, and T-cell antigen receptor (TCAR) alpha beta-. Assays for reverse transcriptase activity and for human T-lymphotropic retroviral sequences in the cellular DNA were negative, indicating that the cells were not transformed by human T-lymphotropic virus (HTLV)-I, HTLV-II, or human immunodeficiency virus (HIV)-I. Culturing the cells in the differentiation inducing agent 12-O-tetradecanoyl phorbol 13-acetate induced an increased expression of CD3 but no other significant changes in T-cell markers. A small population of CD4-negative and CD8-negative T-lymphocytes exist in human peripheral blood and they exhibit natural killer (NK) and antibody-dependent cell-mediated cytotoxic (ADCC) activity. However, the authors' cell line failed to demonstrate such cytotoxic function. The TCAR gene rearrangement studies showed that both T gamma genes were rearranged while the T beta genes were in the germ line configuration and the T delta genes were deleted. HCD8 strongly expressed the antigens Leu M1 and Ki-1, markers detected only rarely on normal unstimulated human T-cells, but quite consistently found on Reed-Sternberg cells and cells of some large pleomorphic T-cell lymphomas. HCD8 may be used to study the control of Leu M1 and Ki-1 expression in T-cells and it may provide some insight into the cellular origin of the above-mentioned lymphomas.
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PMID:A T-cell line with an unusual phenotype. 255 76

Tumor-promoting agents are known to inhibit the specific differentiation processes of several animal cell systems in vitro, including the Friend leukemia cell system. We have examined the effect of 12-O tetradecanoylphorbol-13-acetate (TPA) on the latter system and have investigated its action on Friend virus expression. At a concentration of 16.7 nM, TPA inhibits the dimethyl sulfoxide-induced Friend cell terminal differentiation and, at the same time, enhances the expression of the Friend virus genome, as demonstrated by a 2-fold increase in the amount of reverse transcriptase-containing particles released into the culture fluid and in the levels of virus-specific intracytoplasmic RNA. The greatest effect of TPA is evident after 24 hr of treatment. At this time, TPA exerts also its strongest effect upon the induction of the plasminogen activator. Our results indicate that two specific effects of TPA, i.e., block of differentiation and induction of plasminogen activator, correlate well in the Friend cell system with an extracellular and intracellular increase in virus expression.
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PMID:Enhancement of viral gene expression in Friend erythroleukemic cells by 12-O tetradecanoylphorbol-13-acetate. 615 74

The action of 12-O-tetradecanoylphorbol-13-acetate (TPA) on several retrovirus-related functions was investigated in four virus-host cell systems. The following effects were recorded: (i) in STU-mice, infected with the Friend virus complex (Friend) murine leukaemia virus/Friend spleen focus forming virus) and treated with TPA (50 ng/g) for one week prior to infection, the number of spleen foci increased 5-fold over the control. (ii) Addition of TPA (0.04 to 40 ng/ml) to virus-producing cell systems resulted in a 2-fold increase of extracellular reverse transcriptase activity. The maximum response was observed in Friend leukemia virus-producing mouse cells at 0.1 to 0.4 ng TPA/ml and in simian sarcoma virus-producing rat cells at 4 ng/ml. (iii) The efficiency of transformation of BalbC 3T3 cells by Moloney murine sarcoma virus, tested in a focus formation assay, was slightly enhanced by TPA. (iv) TPA inhibited the induction of endogenous virus formation in B cell mitogen-stimulated spleen cell cultures from BalbC mice.
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PMID:Diverse effects: augmentation, inhibition, and non-efficacy of 12-O-tetradecanoylphorbol-13-acetate (TPA) on retrovirus genome expression in vivo and in vitro. 617 39

The diterpene ester promoter of mouse skin tumors, 12-O-tetradecanoylphorbol-13-acetate (TPA), efficiently induces Epstein-Barr virus (EBV)-associated DNA polymerase (DNA nucleotidyltransferase) activity in the EBV-producing lymphoblastoid cell line, P3HR-1. With the use of intervent dilution chromatography followed by sequential DEAE-cellulose and phosphocellulose column chromatography, the virus-associated enzyme has been isolated and purified 300-fold. The partially purified EBV DNA polymerase activity could be distinguished from cellular polymerases by its activation with salt and its degree of sensitivity to N-ethylmaleimide and phosphonoacetic acid. The enzyme showed maximum activity for copying activated calf thymus DNA in the presence of 100 mM ammonium sulfate. In the absence of salt, the enzyme utilized with high efficiency deoxyoligomer-homopolymer templates, but failed to copy poly(rA) . oligo(dT)10 and oligo(dT)10, showing that the enzyme had properties distinct from DNA polymerase gamma, reverse transcriptase, and terminal deoxynucleotidyltransferase. The partially purified enzyme is strongly inhibited by acyclovir triphosphate and thus has properties similar to herpes simplex virus DNA polymerase.
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PMID:Induction of Epstein-Barr virus-associated DNA polymerase by 12-O-tetradecanoylphorbol-13-acetate. Purification and characterization. 624 99

The tumor promoters 12-O-tetradecanoylphorbol-13-acetate (TPA) and teleocidin were found to be effective in stimulating the synthesis of primate retroviruses in chronically infected human cells. Production of baboon endogenous virus, simian sarcoma virus of woolly monkeys, Mason-Pfizer virus of rhesus monkeys and of a type D isolate from a human cell line was evaluated by assaying particle-associated reverse transcriptase activities in culture fluids of cells grown in the presence or absence of tumour promoters. Both TPA and teleocidin caused a significant but transient increase in virus production, as well as cytomorphological changes in the following infected cell types: human embryonic kidney, Tu 197 human ovarian carcinoma cells, NC 37 human lymphoblastoid line. However, infected A 204 human rhabdomyosarcoma cells were not modified by these promoters. The stimulation of virus production reached its maximum after two to four days, at which time virus production was three to forty times higher than that in controls. The optimal concentration of tumour promoters was 5-10 ng/mL. 12-O-Retinoylphorbol-13-acetate produced a similar but somewhat weaker effect. Control experiments demonstrated that enhancement was specific to those viruses that chronically infected each cell type.
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PMID:Enhancement of primate retrovirus synthesis by tumour promoters. 644 5


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