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)

The TAR element is a viral regulatory element extending from +1 to +60 in the human immunodeficiency virus type 1 (HIV-1) long terminal repeat, which is critical for activation by the transactivator protein Tat. Jurkat cell lines chronically infected with viruses containing HIV-1 TAR element mutations are extremely defective for both gene expression and replication. We previously demonstrated that viruses containing mutations of the TAR RNA stem, bulge, or loop structures have 200- to 5,000-fold-reduced levels of gene expression compared with lymphoid cells harboring wild-type virus. In this study, we characterized several Jurkat cell lines infected with TAR element mutant viruses which spontaneously produced culture supernatants with wild-type-like levels of reverse transcriptase activity. These viral supernatants were used to infect Jurkat cells, and following PCR amplification of the viral long terminal repeats, their DNA sequences were analyzed. This analysis demonstrated that revertant viruses isolated from these cell lines retained the original TAR mutations but also contained additional compensatory mutations within TAR. In gel retardation analysis, recombinant Tat protein bound to higher levels to in vitro-transcribed revertant TAR RNAs than the original TAR RNA mutants. Both the original and revertant TAR elements were inserted into both chloramphenicol acetyltransferase reporter and HIV-1 proviral constructs and assayed following transfection of Jurkat cells. Constructs containing revertant TAR element mutations were capable of strong activation by Tat in contrast to constructs containing the original TAR mutations. Analysis of the secondary structure of TAR RNA sequences suggested that TAR RNA structures which differed from that of wild-type TAR were still capable of strong activation in response to Tat. These results further define critical sequences in TAR RNA that are required for tat activation. In addition, since TAR structures with lower free energy that preserve the loop and bulge structures may be favored over fully formed TAR RNA with higher stable free energy, these results implicate nascent RNA rather than the fully formed TAR RNA structure as the target for tat activation.
...
PMID:Human immunodeficiency virus type 1 TAR element revertant viruses define RNA structures required for efficient viral gene expression and replication. 760 59

We established an improved non-radioactive in situ hybridization (ISH) method to detect mRNA of cytokines in cell preparations and tissues. Via this method we could demonstrate various cytokines in stimulated peripheral blood mononuclear cells (PBMC), lymphoid cell lines and human lymphoid tissues. The probes for the in situ hybridization were made by labelling cytokine-specific PCR products with digoxigenin (Dig) in a repeated PCR. This resulted in an intrinsic labelling of the probe with several Dig-UTP molecules. Incorporation of Dig-11-dUTPs was shown on ethidium bromide-stained agarose gels by a higher molecular weight of the PCR products with incorporated Dig-dUTPs when compared to control PCR products without digoxigenin. Cytospin-centrifuged cells of PHA-stimulated PBMC or lymphoid cell lines and frozen sections of various human lymphoid tissues were hybridized with the Dig-labelled cytokine probes and the hybridized probes were detected immuno-histochemically. In this way, we detected and localized cytokine mRNAs (IL-2, IL-4, IL-6, IL-8, IL-10) in PBMC, in the human T-cell line Jurkat, in the follicular lymphoma cell line DoHH2, and in human lymph nodes and tonsils. The in situ hybridization had a high sensitivity as the results correlated closely with the detection of cytokine mRNA by reverse transcriptase-PCR (RT-PCR) data from the same samples. We showed that Jurkat and DoHH2 cells produce several cytokines constitutively and that, after activation with the phorbol ester PMA, expression of several cytokine mRNAS was enhanced.
...
PMID:An improved, sensitive, non-radioactive in situ hybridization method for the detection of cytokine mRNAs. 765 59

3'-Azido-2',3'-dideoxy-5-iodouridine (AzIdUrd) and 3'-azido-2',3'-dideoxy-5-bromouridine (AzBdUrd), previously shown to be potent and selective inhibitors of human immunodeficiency virus replication in vitro were minimally toxic to the uninfected human lymphoid cell line H9 (IC50 = 197 and 590 microM, respectively). Both compounds strongly inhibited the incorporation of [3H]thymidine but not [3H]deoxyadenosine into DNA, and we observed no significant inhibition of [3H]uridine incorporation into RNA or [3H]amino acid incorporation into protein. Exposure of H9 cells to AzIdUrd or AzBdUrd (100 microM, 24 hr) and pulse-labeling with [3H]thymidine resulted in approximately 80% reduction in levels of tritiated dTMP, dTDP, and dTTP relative to control. [125I]AzIdUrd was phosphorylated rapidly in H9 cells with the monophosphate accounting for over 90% of total soluble radioactivity. A relatively low but stable level of AzIdUTP was maintained over a 12-hr period. [125I]AzIdUrd was phosphorylated by a cell free extract of H9 cells at a rate approximately three times that of thymidine and its phosphorylation was inhibited by excess thymidine. AzIdUrd was found to be a competitive inhibitor of cytosolic thymidine kinase with a Ki of 2.63 microM and AzIdUMP a weak competitive inhibitor of thymidylate kinase with a Ki of 55.3 microM. Both AzIdUTP and AzBdUTP were potent competitive inhibitors of HIV-1 reverse transcriptase (Ki = 0.028 and 0.043 microM, respectively) and relatively poor inhibitors of H9 cell DNA polymerase alpha (Ki = 42.0 and 42.7 microM, respectively). Thus, the high therapeutic index of these compounds is due to the sensitivity of the viral reverse transcriptase, coupled with the relative insensitivity of the host cell DNA polymerase alpha.
...
PMID:Metabolism and mode of selective inhibition of human immunodeficiency virus replication by 3'-azido-2',3'-dideoxy-5-iodouridine and 3'-azido-2',3'-dideoxy-5-bromouridine. 767 40

A new series of potent specific 2-pyridinone reverse transcriptase (RT) inhibitors was developed based on the preliminary development lead 3-[(phthalmido)ethyl]-5-ethyl-6-methylpyridin-2(1H)-one (3), a non-nucleoside derivative which exhibited weak antiviral activity in cell culture against HIV-1 strain IIIB. One compound, 3-[(benzoxazol-2-yl)ethyl]-5-ethyl-6-methylpyridin-2(1H)-one (9,L-696,229), which was a highly selective antagonist of the RT enzyme (IC50 = 23 nM) and which inhibited the spread of HIV-1 IIIB infection by > 95% in MT4 human T-lymphoid cell culture (CIC95 = 50-100 nM), was selected for clinical evaluation as an antiviral agent.
...
PMID:Synthesis and evaluation of 2-pyridinone derivatives as HIV-1-specific reverse transcriptase inhibitors. 4. 3-[2-(Benzoxazol-2-yl)ethyl]-5-ethyl-6-methylpyridin-2(1H)-one and analogues. 768 54

1. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) was an inducer of microsomal benzo[alpha]pyrene hydroxylase (AHH) and 7-ethoxyresorufin O-deethylase (EROD) in MT-4 human lymphoid cell culture. 2. The monoclonal antibody (Mab), 1-7-1 and the immunodepleted polyclonal antibody (Pab), anti-CYP1A1(-A2), inhibit AHH and EROD activities pre-induced by 10 nM TCDD in MT-4 cells. Hence, the specific monooxygenase isoform induced in the lymphoid cells by TCDD appears to be CYP1A1 the expression of which is mediated by the Ah receptor. 3. Incubation of MT-4 cells with TCDD at 10, 50 and 150 nM for 1.5 and 48 h followed by infection of the cells with human immunodeficiency virus 1 (HIV-1) was accompanied by a 3-6-fold increase in the activity of viral RNA-dependent DNA-polymerase. The most marked effect on reverse transcriptase activity occurred with 10 nM TCDD 5-9 days after HIV-1 infection. 4. In the same period there was accumulation of viral protein, determined by ELISA, with a 4-8-fold increase in production of viral protein. The above effects of TCDD have been observed even when MT-4 cells were washed 1.5 h after beginning the incubation with TCDD.
...
PMID:Stimulatory effect of the CYP1A1 inducer 2,3,7,8-tetrachlorodibenzo-p-dioxin on the reproduction of HIV-1 in human lymphoid cell culture. 768 6

Temperature elevation constitutes a beneficial component of the host defence against viral pathogens. However, heat treatment may be detrimental to HTLV-I-infected cells by increasing virion and oncoprotein production. We investigated the effects of thermal elevation on the in vitro replication of HTLV-I (human T-cell leukaemia/lymphoma virus type I) in MT-2 cells, an HTLV-I-transformed lymphoid cell line. We found that HTLV-I replication in MT-2 cells was markedly increased as demonstrated by a nearly 2-fold increase in detection of viral p24 antigen and a 20-fold increase in reverse transcriptase activity during up to 5 h of heat treatment at 42 degrees C. The results suggest that physiologic thermal elevations may induce viral production in HTLV-I-infected individuals.
...
PMID:In vitro thermal enhancement of human T-cell leukaemia/lymphoma virus type I (HTLV-I) in HTLV-I-transformed cells. 768 46

Two new myeloid cell lines (K051 and K052) were established from a patient with multilineage CD7-positive acute leukemia. The K051 and K052 were established from the patient's bone marrow cells at diagnosis and at relapse, respectively. The K051 cell expressed myeloid-associated antigens (CD13 and CD33), a platelet-associated antigen (CD41), and an erythroid antigen (glycophorin A). The K052 cell expressed myeloid-associated antigens (CD13, CD14, and CD33), lymphoid markers (CD2, CD5, and CD7), and HLA-DR. Chromosome analysis of both cell lines showed a 17p- chromosome. Both cell lines were investigated for aberrations of the p53 gene and the N-ras gene. A p53 mutation detected in both cell lines consisted of a C-->T substitution in codon 248. An N-ras mutation detected only in the K052 cell consisted of a G-->C substitution in codon 13. Expression of the multidrug resistance gene (MDR1) was also investigated by the semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). MDR1-mRNA was more highly expressed by the K052 cell than the K051 cell, being equivalent to that in HEL cells. The functional MDR1-protein against vincristine was also observed, and its function was inhibited by verapamile and Cyclosporin A. The K052 cells were capable of phenotypic or morphologic differentiation after being incubated with granulocyte colony-stimulating factor, interleukin-2, phorbol 12-myristate 13-acetate, or 1,25-dihydroxy-vitamin D3. In contrast, the K051 cells responded phenotypically to retinoic acid. Thus, the K051 and K052 cell lines will be useful for investigating the cellular and molecular events in leukemogenesis and differentiation, and the mechanism of expression of the MDR1 gene.
...
PMID:p53 and N-ras mutations in two new leukemia cell lines established from a patient with multilineage CD7-positive acute leukemia. 769 50

Baicalin (BA), (formulated as 7-D-glucuronic acid-5,6-dihydroxy-flavone), was purified from the plant Scutellaria Baicalensis Georgi. It has been used as a traditional Chinese herbal medicine. The inhibitory effect of BA against human immunodeficiency virus (HIV-1) infection and replication has been studied in vitro. The compound inhibits HIV-1 infection and replication as measured by: (1) a quantitative focal syncytium formation on CEM-ss monolayer cells; and (2) HIV-1 specific core antigen p24 expression and retroviral reverse transcriptase (RT) activity in the HIV-1-infected H9 cells. We have further demonstrated that the enzymatic activity of purified recombinant HIV-1/RT was inhibited by BA. In addition to lymphoid cell lines, the anti-HIV-1 activity of BA was also observed in cultures of primary human peripheral blood mononuclear cells infected with HIV-1 in vitro. Neither cytotoxic nor cytostatic effects on the indicator cells were found under the assay condition. This data suggests that BA may serve as a useful drug for the treatment and prevention of HIV infections.
...
PMID:Inhibition of HIV infection by baicalin--a flavonoid compound purified from Chinese herbal medicine. 769 33

During the early stages of human immunodeficiency virus (HIV) infection, although symptoms are absent and viral replication in peripheral blood mononuclear cells is low, substantial levels of HIV replication can be documented in lymphoid tissue [G. Pantaleo, C. Graziosi, J.F. Demarest, L. Butini, M. Montroni, C.H. Fox, J.M. Orenstein, D.P. Kotler, and A.S. Fauci, Nature (London) 362:355-358, 1993, and J. Embretsen, M. Zupancic, J.L. Ribas, A. Burke, P. Racz, K. Tenner-Tacz, and A.T. Haase, Nature (London) 362:359-362, 1993]. This observation suggests that earlier treatment of HIV infection may be indicated and that strategies for enhancing drug targeting to the lymphoid tissue reservoris of HIV infection may be beneficial. To address this issue, we synthesized dioleoylphosphatidyl-ddC (DOP-ddC) and dipalmitoylphosphatidyl-3'-azido-3'-deoxythymidine (DPP-AZT), phospholipid prodrugs which form lipid bilayers and which are readily incorporated into liposomes. The anti-HIV activity of DOP-ddC was similar to that of ddC in HIV type 1-infected HT4-6C cells, but DPP-AZT was considerably less active than AZT in HT4-6C cells. Liposomes containing DOP-[3H]ddC or DPP-[3H]AZT administered intraperitoneally to mice produced greater levels of total radioactivity over time in plasma, spleen, and lymphoid tissue relative to the results with [3H]ddC and [3H]AZT, respectively. DPP-AZT administered intraperitoneally in liposomes as a single daily dose to mice infected with Rauscher leukemia virus prevented increased spleen weight and reverse transcriptase levels in serum with a dose-response roughly comparable to that of AZT given continuously in the drinking water. DOP-ddC, DPP-AZT, and lipid conjugates of other antiretroviral nucleosides may provide higher levels of drug over time in plasma and in lymph nodes and spleen, important reservoirs of HIV infection, and may represent an interesting alternative approach to antiviral nucleoside treatment of AIDS.
...
PMID:Phosphatidylazidothymidine and phosphatidyl-ddC: assessment of uptake in mouse lymphoid tissues and antiviral activities in human immunodeficiency virus-infected cells and in Rauscher leukemia virus-infected mice. 769 64

Expression of the IL-13 gene in malignant tissues from 26 human B-cell lymphoid malignancies was analyzed by reverse transcriptase-polymerase chain reaction (RT-PCR). A positive signal was detected in 16 cases, which included high grade B lymphomas, follicular lymphomas and B-cell chronic lymphocytic leukemias. IL-13 mRNA was also detected in the 9 malignant B cell lines and in the 6 lymphoblastoid cell lines tested, as well as in freshly isolated malignant B cells from 2 patients with a Burkitt's lymphoma. Two of 8 T-cell lymphomas and 2 of 4 T-cell lines expressed the IL-13 gene. In contrast, IL-13 gene expression was not detected in any of the 5 non-lymphoid cell lines tested. No specific binding of radiolabeled IL-13 was detected on B cell lines, suggesting an absence of IL-13 receptors on such cells. This conclusion was also supported by the inability of IL-13 or anti-IL-13 antibodies to affect the growth of malignant B cells. Taken together, these results show that both malignant and EBV-transformed B lymphocytes, either freshly isolated or maintained as cell lines, express the IL-13 gene. This raises the question of the role of B lymphocyte-derived IL-13, a B lymphocyte stimulating cytokine, on the in vivo function of normal B lymphocytes as well as on the in vivo behaviour of B lymphoid malignancies.
...
PMID:Interleukin-13 gene expression by malignant and EBV-transformed human B lymphocytes. 772 91


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

---