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:2.7.11.1 (protein kinase)
81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The double-stranded RNA-activated protein kinase-binding domain (PKRbd) of the NS5A gene of hepatitis C virus (HCV) was studied by the cloning and sequencing method, in HCV-infected patients who had a primary resistance to treatment with interferon (IFN)-alpha (early nonresponders). Patients whose virus load decreased by >or=0.5 log (early responders) were similarly analyzed. In the 2 groups, the PKRbd evolved similarly over the first 24 h. Selection of resistant HCV variants is unlikely to explain primary resistance to IFN-alpha.
...
PMID:Genetic heterogeneity of the NS5A gene of hepatitis C virus and early response to interferon-alpha. 1459 96

We investigated how the hepatitis C virus (HCV) core protein affects the cell cycle profile and cell cycle-related molecules by using the HCV core-expressing stable transfectant. Analysis of the cell cycle profile showed that HCV core impaired G(1) to S transition. The E2F-mediated transcription, phosphorylation of the retinoblastoma protein, and cyclin-dependent kinase (CDK) 4 and CDK2 activities were suppressed in HCV core-expressing cells. The expression levels of G(1) phase-related CDKs/cyclins and various CDK inhibitors were not substantially affected by expression of HCV core. When influences of HCV core on CDK-activating kinase (CAK) were examined, the expression levels of the CAK components, CDK7, cyclin H, and MAT1, were not affected. However, formation of the ternary CAK complex, CAK activity, and the CDK2 level with activating phosphorylation were inhibited by expression of the HCV core. The direct effect of HCV core on CAK was further assessed in the cell-free system by adding the in vitro translated HCV core protein to the anti-CDK7 immunoprecipitate from the cell. The results showed that HCV core led to dissociation of MAT1 from the CAK complex and suppressed the CAK activity. Furthermore, the binding assay revealed that the HCV core was directed against CDK7. Their interaction occurred mainly in the nucleus by the immunostaining. In conclusion, the HCV core protein interacts with CAK and functions as an extrinsic suppressor of CAK. This may be the molecular basis of HCV core-mediated suppression of cell cycle progression. Our findings suggest a novel mechanism concerning HCV core-mediated alteration in the cell cycle machinery.
...
PMID:Hepatitis C virus core functions as a suppressor of cyclin-dependent kinase-activating kinase and impairs cell cycle progression. 1471 30

The aim of this study was to determine whether specific sequences of the phosphorylation homology domain (PePHD) region could be correlated with differences in response to antiviral therapy in patients infected with hepatitis C virus subtypes 1b, 2c, 3a and 4c/d. We included 43 patients (22 sustained responders and 21 nonresponders or relapsers) in the study, who were classified according to early viral decline during the first weeks of antiviral treatment and response at end of follow up. Type of mutations, mutation frequency, genetic diversity and phylogenetic relationships were compared at the PePHD and flanking regions. Phylogenetic trees showed that each sequence clustered together with those of the same subtype. Sequences from subtypes 1b and 4c/d resembled more closely the phosphorylation sites of protein kinase R and eIF2 alpha than sequences from genotypes 2c and 3a, the latter with higher response rates to interferon-alpha (IFN alpha) treatment. However, within specific subtypes, no separate clusters of responders and nonresponders were observed either at the beginning or at the end of follow up. We were not able to find any particular sequence or mutation in the PePHD region or in any other subregion of the fragment studied that allowed prediction of treatment response.
...
PMID:Subtype mutations in the envelope 2 region including phosphorylation homology domain of hepatitis C virus do not predict effectiveness of antiviral therapy. 1473 57

The non-structural protein 5A (NS5A) of hepatitis C virus (HCV) has been implicated in inhibition of antiviral activity of IFN. While previous studies have suggested an interaction between NS5A and the double-stranded RNA-dependent protein kinase (PKR), the possibility still remains that interaction with another molecule(s) is involved in the NS5A-mediated inhibition of IFN. In the present study, we investigated a possible interaction between NS5A and 2',5'-oligoadenylate synthetase (2-5AS), another key molecule in antiviral activity. We observed that NS5A physically interacted with 2-5AS in cultured cells, with an N-terminal portion of NS5A [aa 1-148; NS5A(1-148)] and two separate portions of 2-5AS (aa 52-104 and 184-275) being involved in the interaction. Single point mutations at residue 37 of NS5A affected the degree of the interaction with 2-5AS, with a Phe-to-Leu mutation (F37L) augmenting and a Phe-to-Asn mutation (F37N) diminishing it. Virus rescue assay revealed that the full-length NS5A (NS5A-F) and NS5A(1-148), the latter of which contains neither the IFN sensitivity-determining region (ISDR) nor the PKR-binding domain, significantly counteracted the antiviral activity of IFN. Introduction of a F37N mutation into NS5A(1-148) impaired the otherwise more significant IFN-inhibitory activity of NS5A(1-148). It was also found that the F37N mutation was highly disadvantageous for the replication of an HCV RNA replicon. Taken together, our results suggest the possibility that NS5A interacts with 2-5AS and inhibits the antiviral activity of IFN in an ISDR-independent manner.
...
PMID:Hepatitis C virus NS5A protein interacts with 2',5'-oligoadenylate synthetase and inhibits antiviral activity of IFN in an IFN sensitivity-determining region-independent manner. 1503 38

We have employed a pET-ubiquitin expression system to produce two his-tagged forms of hepatitis C virus (HCV) non-structural protein 5A (NS5A) in Escherichia coli. One derivative contains the full-length protein extended to include a carboxy-terminal hexahistidine tag; the other derivative contains an amino-terminal hexahistidine tag in place of the 32 amino acid amphipathic helix that mediates membrane association. At least 1 mg of each derivative at a purity of 90% could be produced from a 1-L culture. The purified derivatives produced high titer antibody that recognized both p56 and p58 forms of NS5A in Huh-7.5 cells expressing an HCV subgenomic replicon. The NS5A derivatives were efficiently phosphorylated by casein kinase II, leading to at least 5 mol of phosphate incorporated per mole of protein. Interestingly, this level of phosphorylation did not alter the migration of the protein in an SDS-polyacrylamide gel, suggesting that hyperphosphorylation alone is not sufficient to generate the p58 form of NS5A observed in Huh-7 cells. Neither NS5A derivative was capable of inhibiting the eIF2alpha-phosphorylation activity of the activated form of the double-stranded RNA-activated protein kinase, PKR, suggesting that NS5A phosphorylation may be required for this function of NS5A. However, both unphosphorylated derivatives were shown to interact with NS5B, the HCV RNA-dependent RNA polymerase, in solution by using a novel kinase-protection assay. The availability of purified HCV NS5A will permit rigorous biochemical and biophysical characterization of this protein, ultimately providing insight into the function of this protein during HCV genome replication.
...
PMID:Purification and characterization of hepatitis C virus non-structural protein 5A expressed in Escherichia coli. 1529 92

Hepatitis C virus (HCV) core protein is a multifunctional protein that affects transcription and cell growth in vitro and in vivo. Here, we confirm the proliferative activities of core protein in liver and non-liver cells and delineate part of the mechanism whereby core protein promotes cell growth. We show that core protein suppresses the expression of tumor suppressor protein p53 and cyclin-dependent kinase (CDK) inhibitor p21 and enhances the activation of cyclin-dependent kinase 2 (CDK2), the phosphorylation of retinoblastoma (Rb), the activation of the transcription factor E2F-1, and the expression of E2F-1 and S phase kinase-interacting protein 2 (SKP2) genes. Pretreatment of core protein-expressing cells with the inhibitor of CDK2, Butyrolactone I, abolished the phosphorylation of Rb, the activation of E2F-1, and inhibited the expression of E2F-1 gene and cell growth induced. Consistent with these findings, we define a new signaling pathway whereby the HCV core protein mediates cell growth in infected cells.
...
PMID:Activation of RB/E2F signaling pathway is required for the modulation of hepatitis C virus core protein-induced cell growth in liver and non-liver cells. 1538 Dec 53

Hepatitis C virus (HCV) infection is a major problem throughout the world. Combination therapy of interferon (IFN) and ribavirin is the best treatment for eradication at present, but the mechanism is not completely understood. We used the HCV replicon system to investigate this mechanism. The effects of six drugs (UDCA, glycyrrhizin, TJ-9, bezafibrate, ribavirin, and alpha-IFN 2b) on HCV subgenomic RNA (genotype 1b, NS5B 415Y) were examined by reverse transcription polymerase chain reaction, cloning and sequencing. The HCV replication was inhibited by alpha-IFN 2b (7.39-13.2% at 10 U/mL, 3.29-6.12% at 100 U/mL, 1.3-4.86% at 1000 U/mL) and by ribavirin (4.36-13.9% at 100 microg/mL), but not by the other drugs at 24-72 h after treatment. Furthermore, the combination treatment was superior to IFN monotherapy and to ribavirin monotherapy at 72 h post-treatment. Sequence analyses of the double-stranded RNA-activated protein kinase (PKR)-binding domain and flanking regions within the HCV NS5A region revealed that the total numbers of substitutions caused by ribavirin (n = 36) or combination treatment (n = 57) were more than those of IFN alone (n = 5) and controls (n = 6). The HCV replicon system is the most efficient system for HCV replication and is an excellent choice for testing anti-HCV drugs and disinfectants. Our results further suggested that the combination of alpha-IFN 2b and ribavirin might induce mutations, and inhibit HCV RNA synthesis in hepatocytes to a greater extent than ribavirin monotherapy.
...
PMID:Inhibition of subgenomic hepatitis C virus RNA in Huh-7 cells: ribavirin induces mutagenesis in HCV RNA. 1550 May 48

Pegylated interferon (PEG-IFN) alpha combined with ribavirin is the current standard treatment for hepatitis C, but around 50% of patients do not respond for reasons that are not fully understood. To explore the regulation of IFN-inducible protein kinase (PKR), we have measured PKR mRNA levels in peripheral blood mononuclear cells (PBMCs) and in liver biopsies from patients with chronic hepatitis C. PBMCs were also analysed after in vitro incubation with IFN and during antiviral therapy. Non-responders to PEG-IFN plus ribavirin had pre-treatment PKR mRNA levels in PBMCs (0.1+/-0.0074) and in liver (0.102+/-0.051) that were significantly higher than those of responders (PBMCs: 0.023+/-0.014, P=0.0005; liver: 0.034+/-0.020; P=0.0002). On the other hand, PKR mRNA levels in PBMCs were similar in non-responders and in responders after in vitro exposure to IFN (0.434+/-0.301 vs 0.403+/-0.222; P=NS) and during therapy (0.31+/-0.10 vs 0.30+/-0.12; P=NS). These results indicate that in hepatitis C, non-responsiveness to IFN-alpha is associated with pre-treatment up-regulation of the PKR gene, evidence that the infecting hepatitis C virus is able to stimulate endogenous IFN production, being resistant to its antiviral effect. On the other hand, the PKR gene response to exogenous IFN was similar in responders and non-responders, at least in PBMCs, suggesting that variations in its activation are not major determinants of the outcome of antiviral treatment.
...
PMID:PKR gene expression and response to pegylated interferon plus ribavirin therapy in chronic hepatitis C. 1553 1

There is great medical need to develop novel therapies for treatment of human hepatitis C virus (HCV). By gene expression analysis of three HCV-subgenomic RNA replicon cell lines, we identified cellular proteins whose expression is affected by the presence of HCV and therefore may serve as drug targets. Data from cDNA array filter hybridization, as well as from Northern and Western blotting, revealed that the gastrointestinal-glutathione peroxidase (GI-GPx) was drastically down-regulated (up to 20-fold) in all replicon cell lines tested. Concomitantly, total cellular glutathione peroxidase activity was drastically reduced, which rendered these human liver cells more susceptible toward oxidative stress. Interferon alpha caused down-regulation of the HCV-replicon followed by recovery of GI-GPx expression to nearly normal levels. Furthermore, expression of GI-GPx in replicon cells by gene transduction caused down-regulation of HCV RNA in a dose-dependent manner. Moreover, activating the endogenous gene coding for GI-GPx by all-trans-retinoic acid (RA) was sufficient to cause down-regulation of the HCV replicon. A small interfering RNA duplex abrogated GI-GPx up-regulation by RA and concomitantly suppression of HCV. The RA effect was dependent on the presence of sodium selenite, was reversible, and was independent of RNA-activated protein kinase. Taken together, these results show that HCV inhibits the expression of GI-GPx in replicon cells to promote its intracellular propagation. Modulation of GI-GPx activity may open new avenues of treatment for HCV patients.
...
PMID:Expression of gastrointestinal glutathione peroxidase is inversely correlated to the presence of hepatitis C virus subgenomic RNA in human liver cells. 1562 9

The effectiveness of therapy for chronic hepatitis C (CHC) patients has greatly improved in the last few years, and the gold standard is currently held to be pegylated interferon (IFN) in combination with ribavirin. Overall, however, the percentage of patients achieving a sustained virologic response (SVR) is only around 50%,and it is not possible to predict those patients who will benefit from therapy. The molecular mechanisms underlying lack of therapeutic response remain unknown. In this study, we investigated the tissue expression of MxA and RNA-dependent protein kinase (PKR), two antiviral proteins modulated by IFN, in biopsy samples from hepatitis C patients before the beginning of therapy. Our results show that expression of MxA, but not of PKR, is significantly lower in responders compared with nonresponders. No differences were observed regarding the hepatitis C virus (HCV) genotype and the viral load. These results suggest that expression of the MxA protein could play a role among the mechanisms underlying responsiveness to therapy.
...
PMID:MxA and PKR expression in chronic hepatitis C. 1568 19


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

---