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 replication cycle of any virus involves a number of steps, beginning with specific attachment to a cell surface receptor leading eventually to production of progeny viruses by infected cells. In the case of the immunodeficiency virus type-1 (HIV-1), the first step involves a specific interaction between the gp120 viral envelope surface protein and specific CD4 receptor sites at the cell surface. This is followed by penetration of the virus into cells and the formation of proviral double-stranded DNA from single-stranded viral RNA, a process mediated through the action of the viral enzyme called reverse transcriptase. This, in turn, leads to the migration of proviral DNA into the nucleus of the cell and the integration of such DNA within the host cell genome. Finally both viral RNA and viral proteins are produced by the cell's genetic apparatus and new viruses are assembled at the cell surface. The fact that integration of viral DNA into host cell chromosomes occurs means that any cellular replication event will be accompanied by replication of viral DNA. Each of these steps represents a potential target for anti-viral chemotherapy. To date, most efforts to treat HIV-associated disease have focused on the reverse transcription step. In this respect, zidovudine (AZT) has been the most widely used anti-viral drug studied. However, the relative toxicity and lack of efficiency of this drug means that our efforts to develop new therapeutic strategies to combat HIV infection must continue.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Antiviral strategies in the replication of human immunodeficiency virus]. 127 75

Antiviral agents under investigation for the treatment of patients infected with the human immunodeficiency virus (HIV) are reviewed. Multiple mechanisms exist by which antiviral agents might inhibit the replication of HIV or eradicate its latent form in affected cells, or both. These mechanisms include (1) interference with the cell surface receptor for HIV, (2) prevention of uncoating of viral particles, (3) inhibition of reverse transcriptase, (4) prevention of integration and posttranscription processing, (5) interference with viral assembly, and (6) interference with virus release. Most agents developed thus far work by inhibiting HIV reverse transcriptase. Suramin, ribavirin, ammonium 21-tungsten-9-antimoniate (HPA-23), foscarnet (phosphonoformate, PFA), inosine pranobex (isoprinosine), peptide T, ampligen, AL 721, dideoxycytidine, and zidovudine (formerly azidothymidine) have antiretroviral activity in vitro. To date zidovudine is the only antiretroviral agent approved by the FDA as clinically effective. However, zidovudine has serious toxicities, including neutropenia and anemia; in some patients dosage reduction or cessation of therapy may be necessary. Because treatment with zidovudine does not cure HIV infection, numerous studies are under way with other anti-HIV agents. Ultimately, combinations of agents probably will be used to suppress or eradicate HIV. While the search for more efficacious and less toxic treatments continues, the development of zidovudine in such a short time provides hope that progress toward a cure will be made rapidly.
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PMID:Development of antiviral agents for the treatment of human immunodeficiency virus infection. 332 38

In the present study we have observed that interleukin (IL) 1 alpha or IL-1 beta directly induced expression of human immunodeficiency virus (HIV) in the latently infected human promonocytic cell line U1. In addition, IL-1 synergized with IL-6, but not with tumor necrosis factor, in the upregulation of virus expression in U1 cells as measured by accumulation of steady-state mRNAs and production of reverse transcriptase activity. The HIV inductive effect of IL-1 was blocked by transforming growth factor beta, anti-IL-1 antibodies, or monoclonal antibodies directed to the type 1, but not to the type 2, cell surface receptor for IL-1; the latter actually caused enhancement of the IL-1-mediated effect. Unlike tumor necrosis factor alpha, IL-1 either alone or in combination with IL-6 did not induce activation of the transcription activating factor NF-kappa B above the constitutive levels of unstimulated U1 cells. Finally, the IL-1 receptor antagonist effectively blocked IL-1-mediated direct and synergistic inductive effects on virus production. Thus, IL-1 may be an important mediator of HIV expression, and blocking of IL-1 expression and/or its effects may have a potential therapeutic role in the inhibition of HIV expression in infected individuals.
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PMID:Interleukin 1 induces expression of the human immunodeficiency virus alone and in synergy with interleukin 6 in chronically infected U1 cells: inhibition of inductive effects by the interleukin 1 receptor antagonist. 750 10

A platelet-activating factor antagonist, RP 55778, potently suppressed the induction of human immunodeficiency virus (HIV) expression in chronically infected promonocytic U1 cells. RP 55778 inhibited the production of reverse transcriptase activity in U1 cells stimulated with the transcriptionally active inducers of virus production, tumor necrosis factor alpha and phorbol 12-myristate 13-acetate. This effect was correlated only in part with a reduction in the levels of HIV RNA, suggesting that this agent was also affecting posttranscriptional levels of virus production. In this regard, RP 55778 effectively blocked the induction of HIV expression in U1 cells stimulated with interleukin 6 and granulocyte-macrophage colony-stimulating factor, which act predominantly as posttranscriptional activators of HIV expression. Finally, RP 55778 inhibited the production of endogenous tumor necrosis factor alpha in phorbol 12-myristate 13-acetate-stimulated cells, thereby interfering with an autocrine pathway of virus expression. The suppressive effects of RP 55778 on HIV expression appeared to be independent of the platelet-activating factor cell surface receptor on U1 cells. RP 55778 inhibited acute HIV replication in primary T-cell blasts and the proliferative capacity of these cells. This study suggests that RP 55778 may represent potentially useful compounds in the treatment of HIV infection.
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PMID:A platelet-activating factor antagonist, RP 55778, inhibits cytokine-dependent induction of human immunodeficiency virus expression in chronically infected promonocytic cells. 768 1

The first accepted report of a novel human, slow virus disease belonging to "lentivirus" known as acquired immunodeficiency syndrome can be traced to reports of June 1981. HIV-1 and HIV-2 were later found over the period 1984-86 to be unequivocally associated with AIDS. They are two serologically distinct viruses belonging to the same family with the unique properties of integration and latency in the host cell genome and the presence of reverse transcriptase. Typical of all retroviruses, the HIV genome comprises three genes governing the synthesis of all core proteins, replication protein encoding, and envelope proteins. HIV uses the CD4 antigen on T-helper cells, and about 40% of blood monocytes and tissue macrophages as a cell surface receptor. HIV may, however, also infect cells which contain no CD4. Macrophages serve as the main reservoir of HIV and may carry the virus to different organs. Very recently a rare type of white blood cell called the dendritic cell has been found to allow for direct infection by HIV during sexual intercourse. These cells are prominently present in the anal and vaginal mucosa. The authors discuss facts and figures on the HIV epidemic, the Indian scenario, classification of the clinical spectrum, the enzyme immunoassay HIV testing format, Western blot, immunofluorescence antibody, HIV culture, flow cytometry, radio immuno precipitation assay, and the detection of HIV DNA. Significant advances have been made over the last ten years in understanding the pathogenesis of HIV infection and accurately diagnosing infected individuals, with recombinant technology, polymerase chain reaction, and the construction of synthetic hybrid virus rapidly becoming part of routine diagnostics. More sensitive, specific, and rapid techniques are, however, needed for the early diagnosis and management of AIDS cases. The need for more ideal antibody incorporating both regulatory and structural proteins of the virion, preferably manufactured using recombinant or peptide synthesis technique, with high purity and concentrations must be viewed seriously.
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PMID:Science challenging HIV infection. 827 85

Cyclophilin A (CyPA) is incorporated into human immunodeficiency virus type 1 (HIV-1) virions via contact with the Gag polyprotein. Genetic or pharmacologic disruption of CyPA incorporation causes a quantitative reduction in virion infectivity with no discernible effects on virion assembly or on endogenous reverse transcriptase activity. Instead, the reduction of virion-associated CyPA is accompanied by a parallel, quantitative decrease in the initiation of viral DNA synthesis after infection of T cells. The infectivity of CyPA-deficient virions is not restored by pseudotyping with Env of amphotropic murine leukemia virus, demonstrating that CyPA is not required for the HIV-1-Env-CD4 interaction. These results indicate that CyPA is required for an early step in the HIV-1 life cycle following receptor binding and membrane fusion but preceding reverse transcription. CyPA is the first cellular protein other than the cell surface receptor shown to be required for an early event in the life cycle of a retrovirus.
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PMID:Cyclophilin A is required for an early step in the life cycle of human immunodeficiency virus type 1 before the initiation of reverse transcription. 864 89

The Fas antigen is a cell surface receptor that, when engaged by Fas ligand or specific agonistic antibodies, triggers apoptosis. The effect of an agonistic monoclonal antibody to mouse Fas antigen (Fas mAb, clone J02) on the viability of cells from dispersed mouse corpora lutea (CL cultures) was tested. Cultures were prepared by enzymatic digestion of CL from day 4-7 pseudopregnant mice. Cultures were pretreated with 0, 1, 10, 100, or 1000 U/ml murine interferon-gamma (IFN) at 72 h of culture. IFN has been shown to increase Fas antigen expression in a number of cell types. At 96 h (time zero), cultures were treated with Fas mAb or IgG. By 4 h after Fas mAb treatment, discrete homogeneous patches of cells within the cultures showed characteristic signs of apoptosis, including blebbing of cell membranes, detachment, and disappearance from the culture. CL cultures contain luteal, stromal, and endothelial cells; fibroblasts; and surface epithelial cells (OSE). Cells dying in response to Fas mAb were identified as OSE. Affected cells had the cobblestone appearance and distinct nuclei typical of epithelial cells. Unlike luteal cells, OSE did not stain with the lipophilic dye, Nile red. The cells did not stain with acetylated low density lipoprotein conjugated to the fluorescent marker octadecyl indocarbocyanine, a marker for endothelial cells and monocytes. Cells in patches stained positively for cytokeratin, a marker for epithelial cells. Fas-mediated cytotoxicity was quantified by counting the number of cells present in discrete patches of OSE 0 and 8 h after Fas mAb treatment. Fas mAb treatment had no effect in cultures pretreated with 0 or 1 U/ml IFN, but induced significant death of OSE in cultures pretreated with 10, 100, and 1000 U/ml IFN (37 +/- 11%, 54 +/- 18%, and 60 +/- 11%, respectively). There was no apparent effect of Fas mAb on other cell types within the CL cultures. To confirm that cells dying in response to Fas mAb were OSE, experiments were also performed on enriched cultures of OSE prepared by enzymatic digestion of the outer surface of the ovary. In enriched OSE cultures pretreated with 200 U/ml IFN, there was 44% killing in response to Fas mAb, whereas in cells not pretreated with IFN, there was no effect. In situ fluorescent end labeling of DNA in CL cultures indicated that treatment with IFN and Fas mAb induced DNA fragmentation in OSE typical of apoptosis. Immunocytochemistry of CL cultures indicated that Fas antigen was expressed in OSE pretreated with IFN. Quantitative reverse transcriptase-PCR showed that IFN pretreatment increased Fas antigen messenger RNA levels 2.3-fold in enriched cultures of OSE. In summary, OSE in CL cultures and enriched cultures of OSE undergo apoptosis in response to Fas mAb when pretreated with IFN. In vivo, OSE undergo programmed cell death before ovulation and rapidly proliferate to repair the surface of the ovulatory follicle after ovulation. Most ovarian cancers are derived from the OSE. The results have implications for both normal ovarian function and oncogenesis in the ovary.
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PMID:Fas antigen-mediated apoptosis of ovarian surface epithelial cells. 934 78

Interferon gamma (IFNgamma) inhibits the growth and differentiation of highly purified human erythroid colony-forming cells (ECFCs) and induces erythroblast apoptosis. These effects are dose- and time-dependent. Because the cell surface receptor known as Fas (APO-1; CD95) triggers programmed cell death after activation by its ligand and because incubation of human ECFCs with IFNgamma produces apoptosis, we have investigated the expression and function of Fas and Fas ligand (FasL) in highly purified human ECFCs before and after incubation with IFNgamma in vitro. Only a small percentage of normal human ECFCs express Fas and this is present at a low level as detected by Northern blotting for the Fas mRNA and flow cytometric analysis of Fas protein using a specific mouse monoclonal antibody. The addition of IFNgamma markedly increased the percentage of cells expressing Fas on the surface of the ECFCs as well as the intensity of Fas expression. Fas mRNA was increased by 6 hours, whereas Fas antigen on the cell surface increased by 24 hours, with a plateau at 72 hours. This increase correlated with the inhibitory effect of IFNgamma on ECFC proliferation. CH-11 anti-Fas antibody, which mimics the action of the natural FasL, greatly enhanced IFNgamma-mediated suppression of cell growth and production of apoptosis, indicating that Fas is functional. Expression of FasL was also demonstrated in normal ECFCs by reverse transcriptase-polymerase chain reaction and flow cytometric analysis with specific monoclonal antibody. FasL was constitutively expressed among erythroid progenitors as they matured from day 5 to day 8 and IFNgamma treatment did not change this expression. Apoptosis induced by IFNgamma was greatly reduced by the NOK-2 antihuman FasL antibody and an engineered soluble FasL receptor, Fas-Fc, suggesting that Fas-FasL interactions among the ECFCs produce the erythroid inhibitory effects and apoptosis initiated by IFNgamma.
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PMID:Fas ligand is present in human erythroid colony-forming cells and interacts with Fas induced by interferon gamma to produce erythroid cell apoptosis. 945 53

Parathyroid hormone-related protein (PTHrP) is strongly expressed in the epidermis and has been implicated in the regulation of growth and differentiation of keratinocytes. PTHrP has N-terminal sequence homology with parathyroid hormone (PTH) and binds to the type I PTH/PTHrP receptor, but earlier reports suggest that keratinocytes do not possess this cell surface receptor. In order to determine which PTHrP mRNA isoforms are expressed by keratinocytes and whether the type I receptor mRNA is present, we designed specific primers for reverse transcriptase-polymerase chain reaction. The interaction of PTHrP with other promoters of keratinocyte differentiation is unclear. In particular, 1,25(OH)2D3 is also fundamental in calcium homeostasis and induces changes in intracellular calcium. We therefore investigated the effect of 1,25(OH)2D3 on PTHrP mRNA expression and protein production in cultured human keratinocytes. Cells were incubated for 3 days at concentrations of 1.25(OH)2D3 of 10(-10)-10(-6) mol/L. PTHrP in culture supernatant, measured by two site immunoradiometric assay, was 915 +/- 98 PTHrP fmol/mg of cell layer protein in untreated cultures decreasing to 570 +/- 113 with 10(-8) mol/L and 402 +/- 24 with 10(-6) mol/L 1,25(OH)2D3 (mean +/- SEM, P < 0.01, n = 6). Transcripts for all three PTHrP isoforms (139, 141 and 173 amino acids) were detectable in keratinocyte mRNA. Corresponding to the decrease in PTHrP protein we demonstrated a reduction in all three PTHrP mRNA transcripts after 3 days' incubation with 1,25(OH)2D3 over a concentration range 10(-10)-10(-6) mol/L. Repeated studies failed to detect type I PTH/PTHrP receptor mRNA in human keratinocytes, either in control cultures or in the presence of 1,25(OH)2D3. We have shown that keratinocytes produce abundant PTHrP and that this is modulated by 1,25(OH)2D3, suggesting a physiological role. Further studies are required to investigate the relative expression of PTHrP isoforms, their role in keratinocyte signalling and the receptors involved.
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PMID:Human keratinocytes express transcripts for three isoforms of parathyroid hormone-related protein (PTHrP), but not for the parathyroid hormone/PTHrP receptor: effects of 1,25(OH)2 vitamin D3. 974 54

Receptor for hyaluronan (HA)-mediated motility (RHAMM) is a receptor for HA-mediated motility and its expression is correlated with malignancy of ras-transformed cells in that binding of HA to this receptor activates their migratory ability. CD44, a cell surface receptor for HA is also implicated in metastatic behavior of some cancer cells. In this study we examined the relationships of cancer progression with mRNA levels of RHAMM, CD44 (all forms), and exon 6 of CD44 using the real-time reverse transcriptase-polymerase chain reaction method in specimens of colon cancers at different diagnostic stages from 30 patients. Increased mRNA levels of RHAMM were observed in 29 specimens (97%), CD44s (all forms) in 21 specimens (70%), and its exon 6 in 19 specimens (63%) in comparison with those in the corresponding noncancerous tissue specimens. A statistically significant correlation between RHAMM expression and cancerous specimens at any of Dukes' stages A, B, and C was found, and the overexpression of CD44 mRNAs was confirmed in specimens at Dukes' stage C. Thus, our present study for the first time suggests that RHAMM expression may be a clinically useful indicator of colon cancer.
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PMID:Receptor for hyaluronan-mediated motility and CD44 expressions in colon cancer assessed by quantitative analysis using real-time reverse transcriptase-polymerase chain reaction. 1055 29


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