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:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Interleukin-10 (IL-10) has been used in the treatment of viral hepatitis in interferon-alpha (IFN-alpha) non-responders while patients who have high levels of IL-10 are poorly responsive to IFN-alpha. The mechanism underlying such controversial functions of IL-10 remains unknown. Here we demonstrated that injection of IL-10 into mice attenuated IFN-alpha-induced signal transducer and activator transcription factor (STAT)1 tyrosine phosphorylation in the liver. Reverse transcriptase-polymerase chain reaction assay demonstrated that mouse liver expressed high levels of IL-10 receptor 2 (IL-10R2) but low levels of IL-10R1. Injection of IL-10 into mice activated STAT3 but not STAT1 tyrosine phosphorylation and induced suppressor of cytokine signal 2 (SOCS2), SOCS3, and cytokine-inducible SH2 protein (CIS) mRNA expression in the liver. Furthermore, overexpression of SOCS2 or SOCS3 inhibited IFN-alpha-induced reporter activity in hepatic cells. These findings suggest that IL-10 inhibits IFN-alpha-activated STAT1 in the liver, at least in part, by inducing SOCS2, SOCS3, and CIS expression, which may be responsible for the resistance of IFN-alpha therapy in patients who have high levels of IL-10 and recommends that IL-10 treatment for viral hepatitis should be cautious.
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PMID:IL-10 attenuates IFN-alpha-activated STAT1 in the liver: involvement of SOCS2 and SOCS3. 1103 14

The ribonucleoside analog ribavirin (1-beta-D-ribofuranosyl-1,2, 4-triazole-3-carboxamide) shows antiviral activity against a variety of RNA viruses and is used in combination with interferon-alpha to treat hepatitis C virus infection. Here we show in vitro use of ribavirin triphosphate by a model viral RNA polymerase, poliovirus 3Dpol. Ribavirin incorporation is mutagenic, as it templates incorporation of cytidine and uridine with equal efficiency. Ribavirin reduces infectious poliovirus production to as little as 0. 00001% in cell culture. The antiviral activity of ribavirin correlates directly with its mutagenic activity. These data indicate that ribavirin forces the virus into 'error catastrophe'. Thus, mutagenic ribonucleosides may represent an important class of anti-RNA virus agents.
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PMID:The broad-spectrum antiviral ribonucleoside ribavirin is an RNA virus mutagen. 1110 Jan 23

Hepatitis C virus infection is a major health burden affecting an estimated 200 million people worldwide. Chronic hepatitis C is one of the leading causes of cirrhosis and end-stage liver cirrhosis; thus effective therapies are required. For many years interferon-alpha has been the treatment of choice for patients with chronic hepatitis C infection. However, in only 10%-15% of patients is interferon-alpha monotherapy successful, leading to sustained virological response. A combination of interferon-alpha and ribavirin significantly enhanced sustained virological response rates to 40%. Strategies to further improve response rates include modification of the interferon dosing schedule with induction dosing and daily interferon, new interferons such as consensus interferon, or interferon with longer half-life and more favorable pharmacokinetics such as pegylated interferons. Recent trials showed that a combination of pegylated interferons and ribavirin leads to sustained response rates of about 50% with an acceptable safety profile. Hopefully, new treatment modalities will be available in the near future. Helicase, protease and the RNA polymerase are potential targets to suppress HCV replication and several immunotherapeutic approaches are explored.
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PMID:Current and future treatment of hepatitis C. 1129 80

Ribavirin is administered in combination with interferon-alpha for treatment of hepatitis C virus (HCV) infection. Recently, we demonstrated that the antiviral activity of ribavirin can result from the ability of a viral RNA polymerase to utilize ribavirin triphosphate and to incorporate this nucleotide with reduced specificity, thereby mutagenizing the genome and decreasing the yield of infectious virus (Crotty, S., Maag, D., Arnold, J. J., Zhong, W., Lau, J. Y., Hong, Z., Andino, R., and Cameron, C. E. (2000) Nat. Med. 6, 1375-1379). In this study, we performed a quantitative analysis of a novel HCV RNA polymerase derivative that is capable of utilizing stably annealed primer-template substrates and exploited this derivative to evaluate whether lethal mutagenesis of the HCV genome is a possible mechanism for the anti-HCV activity of ribavirin. These studies demonstrate HCV RNA polymerase-catalyzed incorporation of ribavirin opposite cytidine and uridine. In addition, we demonstrate that templates containing ribavirin support CMP and UMP incorporation with equivalent efficiency. Surprisingly, templates containing ribavirin can also cause a significant block to RNA elongation. Together, these data suggest that ribavirin can exert a direct effect on HCV replication, which is mediated by the HCV RNA polymerase. We discuss the implications of this work on the development of nucleoside analogs for treatment of HCV infection.
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PMID:Hepatitis C virus RNA-dependent RNA polymerase (NS5B) as a mediator of the antiviral activity of ribavirin. 1160 68

For patients with chronic myeloid leukaemia, methods for monitoring response to treatment have changed considerably in recent years. In the 1980s, the principal approach was repeated examination of bone marrow metaphases for the presence of the Ph chromosome in patients treated by interferon-alpha (IFN-alpha) or allogeneic stem cell transplantation. The use of fluorescence in situ hybridisation (FISH) techniques to detect the BCR-ABL fusion gene in Ph-positive leukaemia cells increased the sensitivity of cytogenetic studies to some degree. In the last 10 years, the reverse-transcriptase polymerase chain reaction (RT-PCR) has proved extremely valuable for assessing and monitoring minimal residual disease in patients who achieve Ph negativity after treatment with IFN-alpha or with the new Abl tyrosine kinase inhibitor imatinib mesylate or after allogeneic stem cell transplantation (SCT). Results are consistent with the notion that the majority of long-term survivors after allogeneic SCT are probably 'cured'; for other patients monitored serially in complete cytogenetic remission, rising numbers of BCR-ABL transcripts detected by RT-PCR can indicate the need for further therapy.
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PMID:Cytogenetic and molecular monitoring of residual disease in chronic myeloid leukaemia. 1191 87

It is known that nuclear DNA helicase II (NDH II) links CREB-binding protein directly to RNA polymerase II holoenzyme, and that this interaction is essential for gene activation by CREB. Here, we report for the first time that some NDH II/RNA helicase A is a component of promyelocytic leukemia nuclear bodies (PML NBs). An autoimmune serum specific for PML NBs was identified and used in immunoprecipitation experiments. NDH II was present in the immunoprecipitates as shown by mass spectrometry and by immunoblotting. Immunofluorescence and ultrastructural studies showed that NDH II colocalizes with a small subset of PML NBs in control cells, however, colocalizes with practically all bodies in interferon-alpha-stimulated cells. After interferon stimulation, more PML NBs were found to contain newly synthesized RNA, as indicated by bromouridine incorporation. PML NBs also contain RNA polymerase II. The association of NDH II with PML NBs was transcriptionally dependent, and NDH II was present in all bodies with nascent RNA. Blocking of mRNA synthesis caused NDH II relocalization from nucleoplasm to nucleoli. Based on the data, we suggest that NDH II recruitment to PML NBs is connected with transcriptional regulation of interferon-alpha-inducible genes attached to PML NBs.
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PMID:Nuclear DNA helicase II is recruited to IFN-alpha-activated transcription sites at PML nuclear bodies. 1216 69

The role of T cells in eradicating leukemic cells has been well demonstrated for chronic myeloid leukemia (CML). Type 1 (T1) T-cell cytokines play a major role in this antileukemic immune effect. Studies in cancer patients have demonstrated a decreased T1 cytokine production, measured by enzyme-linked immunosorbent assay (ELISA), in cultures of peripheral blood mononuclear cells. This observation of malignancy-related suppressed T1 cytokines also occurs in untreated chronic-phase (CP) CML, raising the question of the influence of different CML treatment regimens on this immunosuppression. Intracellular flow cytometry (ICF) has facilitated the evaluation of cytokines on a single-cell level. This study analyzed T1 (interferon-gamma) cytokine production in purified peripheral blood T cells by ICF, comparing different therapy approaches for CML. Twenty-one newly diagnosed CP CML patients were compared with 24 patients treated with interferon-alpha (IFN-alpha) and to 30 allogeneic bone marrow transplant (BMT) recipients (BCR-ABL negative by reverse-transcriptase polymerase chain reaction, and free of, or having only limited graft-versus-host disease at the time of study). Thirty-seven healthy controls were included. Our results showed a significantly decreased T-cell IFN-gamma synthesis in CP CML patients in relation to healthy controls (P = 0.0007). Treatment with IFN-alpha resulted in a shift from immunosuppression--documented for the group of untreated patients--to immunopotentiation, with an increase of T-cell IFN-gamma production (P = 0.0266). Notably, BMT enhanced IFN-gamma production of T cells to a level not only exceeding untreated patients (P < 0.0001) but also healthy volunteers (P < 0.0001). The observation of T1 cytokine up-regulation with IFN-alpha therapy indicates that enhanced T-cell function may be achievable in patients with CML, even in the absence of an allo-response.
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PMID:Intracellular cytokine analysis of interferon-gamma in T cells of patients with chronic myeloid leukemia. 1260 98

Ribavirin is a broad spectrum antiviral nucleoside that displays activity against a variety of RNA and DNA viruses. Ribavirin is currently used in combination with interferon-alpha for the treatment of hepatitis C virus (HCV) infection and was recently shown to be directly incorporated by the HCV RNA polymerase into RNA products. This capacity ultimately leads to increased mutation rates and drastically reduces the viral fitness. As a first step toward elucidating the nature of the specific interaction between ribavirin and the HCV polymerase, we have utilized fluorescence spectroscopy to monitor precisely the binding of ribavirin triphosphate (RTP) to the viral polymerase. This spectroscopic approach allowed us to clearly separate the RTP binding activity from the concomitant catalytic steps. We report here the first detailed study of the binding kinetics and thermodynamic parameters involved in the interaction between RTP and an RNA polymerase. We demonstrate that RTP binds to the same active site as nucleotides. Furthermore, we provide evidence that the HCV polymerase cannot only bind to RTP but also to nonphosphorylated ribavirin, albeit with less affinity. By using various combinations of template-primers, we also demonstrate that base pairing is not involved in the initial binding of RTP to the HCV polymerase. Based on the results of circular dichroism and denaturation studies, we show that the RNA polymerase undergoes subtle conformational changes upon the binding of RTP, although the interaction does not significantly modify the stability of the protein. Finally, although metal ions are required for catalytic activity, they are not required for the initial binding of RTP to the polymerase. Such quantitative analyses are of primary importance for the rational design of new ribavirin analogues of potential therapeutic value and provide crucial insights on the interaction between RTP and the HCV RNA polymerase.
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PMID:Initial binding of the broad spectrum antiviral nucleoside ribavirin to the hepatitis C virus RNA polymerase. 1456 44

Recently, a benzo-1,2,4-thiadiazine was shown to be a potent, specific inhibitor of the hepatitis C virus (HCV) RNA polymerase [J. Biol. Chem. 277 (2002) 32327]. Herein, we present several lines of evidence to demonstrate that thiadiazine compound 4 (C(21)H(21)N(3)O(4)S) is highly synergistic with interferon-alpha (IFN-alpha) and disrupts HCV replicon RNA synthesis with a distinct kinetic profile. A time course analysis after a single treatment with 5 microM compound 4 showed a loss of viral RNA consistent with replicon RNA half-life, suggesting inhibition of 90% of ongoing or newly initiated replicative intermediates. This finding is consistent with the mechanism of action recently reported for compound 4, an RNA synthesis initiation inhibitor [J. Biol. Chem. 278 (2003) 16602]. Further, unlike IFN-alpha, an immediate reduction of HCV replicon RNA synthesis was apparent upon addition of compound 4. Treatment with IFN-alpha showed a delay of approximately 4h prior to inhibition of viral RNA replication, consistent with its signaling kinetics.
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PMID:Kinetic profile of a heterocyclic HCV replicon RNA synthesis inhibitor. 1462 24

Actin is abundant in the nucleus and has been implicated in transcription; however, the nature of this involvement has not been established. Here we demonstrate that beta-actin is critically involved in transcription because antibodies directed against beta-actin, but not muscle actin, inhibited transcription in vivo and in vitro. Chromatin immunoprecipitation assays demonstrated the recruitment of actin to the promoter region of the interferon-gamma-inducible MHC2TA gene as well as the interferon-alpha-inducible G1P3 gene. Further investigation revealed that actin and RNA polymerase II co-localize in vivo and also co-purify. We employed an in vitro system with purified nuclear components to demonstrate that antibodies to beta-actin block the initiation of transcription. This assay also demonstrates that beta-actin stimulates transcription by RNA polymerase II. Finally, DNA-binding experiments established the presence of beta-actin in pre-initiation complexes and also showed that the depletion of actin prevented the formation of pre-initiation complexes. Together, these data suggest a fundamental role for actin in the initiation of transcription by RNA polymerase II.
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PMID:Actin is part of pre-initiation complexes and is necessary for transcription by RNA polymerase II. 1551 91


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