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:2.7.7.48 (transcriptase)
9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Infection with the hepatitis C virus (HCV) is the major cause of nonA-nonB hepatitis worldwide. Although this virus cannot be cultivated in vitro, several of its key features have been elucidated in the past few years. The viral genome is a positive-sense, single-stranded, 9.6 kb long RNA molecule. The viral genome is translated into a single polyprotein of about 3000 amino acids. The viral polyprotein is proteolytically processed by the combination of cellular and viral proteinases in order to yield all the mature viral gene products. The genomic order of HCV has been shown to be C-E1-E2-p7-NS2-NS3-NS4A-NS4B-NS5A-NS5B. C, E1 and E2 are the virion.structural proteins. The function of p7 is currently unknown. These proteins have been shown to arise from the viral polyprotein via proteolytic processing by the host signal peptidases. Generation of the mature nonstructural proteins, NS2 to NS5B, relies on the activity of viral proteinases. Cleavage at the NS2/NS3 junction is accomplished by a metal-dependent autocatalytic proteinase encoded within NS2 and the N-terminus of NS3. The remaining cleavages downstream from this site are effected by a serine proteinase also contained within the N-terminal region of NS3. NS3 also contains an RNA helicase domain at its C-terminus. NS3 forms a heterodimeric complex with NS4A. The latter is a membrane protein that has been shown to act as a cofactor of the proteinase. While no function has yet been attributed to NS4B, it has recently been suggested that NS5A is involved in mediating the resistance of the hepatitis C virus to the action of interferon. Finally, the NS5B protein has been shown to be the viral RNA-dependent RNA polymerase.
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PMID:Molecular virology of the hepatitis C virus. 1062 60

The family of the Flaviviridae contains 3 genera: (i) the hepaciviruses, to which belongs Hepatitis C virus (HCV), (ii) the flaviviruses and (iii) the pestiviruses. Over 140 million people, more than four times the number of HIV-positive individuals, are chronically infected with the HCV. Hepatitis G virus (HGV) has not yet been assigned to a genus. The impact of this recently discovered virus is yet to be established. Infections with flaviviruses such as Yellow Fever virus (YFV), Dengue Fever virus (DENV), Japanese Encephalitis virus (JEV) and Tick-borne Encephalitis virus (TBEV) are emerging world-wide. The Pestiviruses, Bovine Viral Diarrhea virus (BVDV), Classical Swine Fever virus (CSFV) and Border Disease virus (BDV) have a serious impact on life-stock. At present, only treatment with interferon, alone or combined with ribavirin, has been approved for the treatment of HCV infections. No specific antivirals are available for the treatment of infections with Hepaci-, Flavi- or Pestiviruses. Possible targets for inhibition of the replication of Flaviviridae are the binding to, and the uptake of the virus in the cell; the internal ribosomal entry site (IRES) of Hepaci- and Pestiviruses; viral proteases; the viral RNA-dependent RNA polymerase and the viral helicase. The search for specific inhibitors of HCV replication is hindered by the absence of an efficient cell culture system for propagation of this virus. In addition, small laboratory animals, including mice, are not susceptible to HCV infection. Flaviviruses may cause infection in mice, but do so mainly following direct intracerebral inoculation. We have established a small animal model for flavivirus infections in SCID mice inoculated peripherally with the murine flavivirus Modoc.
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PMID:Infections with flaviviridae. 1065 76

Infection with high-risk human papillomaviruses (HPV), is the most significant risk factor for cervical cancer and it may be possible to prevent this malignancy by immunisation. Before immunisation programmes can be designed, however, it is necessary to know the age of acquisition and all routes of infection for these viruses. Sexual transmission is well documented and vertical transmission has also been demonstrated, although the frequency of transmission remains controversial. We previously showed that vertical transmission frequently results in persistent infection, and now present data on the prevalence of HPV-16 DNA (the most prevalent high-risk HPV type) in healthy children. Buccal samples from 267 healthy children aged 3-11 years were tested for HPV DNA by generic PCR (MY09/MY11), and a HPV-16 specific nested PCR. Reverse transcriptase (RT)-PCR was used to determine the prevalence of transcriptionally active HPV-16 infection in a subset of children. HPV-16 DNA was detected by nested PCR in 138 of 267 (51.7%) samples, whereas HPV DNA was detected in only 45 (16.8%) specimens by generic PCR, that has a lower analytical sensitivity. There were no significant differences in prevalence according to age or sex. Early region mRNA was detected by RT-PCR in six (11.3%) of 53 HPV-16 E5 DNA positive samples. HPV-16 E5 DNA sequences from 10 children confirmed the identity of the sequences detected and identified 13 HPV-16 variants.
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PMID:High prevalence of human papillomavirus type 16 infection among children. 1074 35

Infections with Haemonchus contortus are a major constraint on ruminant health world-wide. Young lambs are very sensitive to Haemonchus infection. Older lambs and sheep acquire immunity after a continuous or seasonal exposure to the parasite. The mechanisms underlying immunity are still not completely understood. Antibodies, in particular local IgA and IgE, certainly play a role. The role of IgG is less clear. Lymphocyte proliferation responses seem to correlate to immunity. Sheep that have high antigen-induced lymphocyte responses have a low susceptibility to infection. Furthermore, several studies have demonstrated that immunity against H. contortus is associated with mastocytosis and hyper-sensitivity reactions. More recently, increasing attention is being paid to the role of cytokines (interleukins and gamma-interferon) in the activation of specific defence mechanisms. Reverse transcriptase-polymerase chain reaction (RT-PCR) assays to study cytokine mRNA expression have become available. The inability of young lambs to mount a significant Th2 response, which is normally characterized by high IgE levels, mastocytosis and eosinophilia, may account for the phenomenon of unresponsiveness in these animals.
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PMID:Immunological responses of sheep to Haemonchus contortus. 1087 10

Infection with the hepatitis C virus (HCV) is the major cause of non-A, non-B hepatitis worldwide. The viral genome, a positive-sense, single-stranded, 9.6-kb long RNA molecule, is translated into a single polyprotein of about 3,000 amino acids. The viral polyprotein is proteoytically processed to yield all the mature viral gene products. The genomic order of HCV has been determined to be C-->E1-->E2-->p7-->NS2-->NS3-->NS4A-->NS4B-->NS5A++ +-->NS5B. C, E1, and E2 are the virion structural proteins. Whereas the function of p7 is currently unknown, NS2 to NS5B are thought to be the nonstructural proteins. Generation of the mature nonstructural proteins relies on the activity of viral proteinases. Cleavage at the NS2-NS3 junction is accomplished by a metal-dependent autocatalytic proteinase encoded within NS2 and the N-terminus of NS3. The remaining downstream cleavages are effected by a serine proteinase contained also within the N-terminal region of NS3. NS3, in addition, contains an RNA helicase domain at its C-terminus. NS3 forms a heterodimeric complex with NS4A. The latter is a membrane protein that acts as a cofactor of the proteinase. Although no function has yet been attributed to NS4B, NS5A has been recently suggested to be involved in mediating the resistance of the HCV to the action of interferon. Finally, the NS5B protein has been shown to be the viral RNA-dependent RNA polymerase. This article reviews the current understanding of the structure and the function of the various HCV nonstructural proteins with particular emphasis on their potential as targets for the development of novel antiviral agents and vaccines.
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PMID:Biochemical and immunologic properties of the nonstructural proteins of the hepatitis C virus: implications for development of antiviral agents and vaccines. 1089 33

The aim of this study was to generate urgently needed data on respiratory pathogens in German children using an economical and efficient tool. Nasopharyngeal aspirates of hospitalized children 0-16 years of age with an acute respiratory tract infection were tested by a nine-valent multiplex reverse-transcriptase polymerase chain reaction. Of 1281 children, 449 (35%) had an acute respiratory tract infection caused by at least one of the organisms studied; there were 29 cases of dual infection. At least 34-42% of severe acute respiratory tract infections in children under 5 years of age were caused by viruses. In children over 5 years of age, this proportion was 23% (P<0.001). Infection during the first 2 years of life was most frequently due to respiratory syncytial virus (n = 162 cases). Parainfluenza virus type 3 (n = 22) and type 1 (n = 14) were detected almost exclusively in children under 5 years of age. Influenza A (n = 90) and adenoviruses (n = 98) were prevalent in all age groups. The frequency of influenza B virus isolation (n = 17) rose significantly after the age of 5 years. Mycoplasma pneumoniae infection (n = 24 cases, 5.2%) was most frequent in 5- to 16-year-old patients. Only one case of Chlamydia pneumoniae infection was found. Since the distribution of pathogens within the different types of lower respiratory tract infections is very similar, it seems that host factors determine which form of lower respiratory tract infection develops in an individual patient. The multiplex reverse-transcriptase polymerase chain reaction may, in the future, become an important tool for epidemiological studies as well as for individual diagnosis.
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PMID:Epidemiological investigation of nine respiratory pathogens in hospitalized children in Germany using multiplex reverse-transcriptase polymerase chain reaction. 1089 33

Canine distemper virus (CDV) has been rescued from a full-length cDNA clone. Besides Measles virus (MV) and Rinderpest virus, a third morbillivirus is now available for genetic analysis using reverse genetics. A plasmid p(+)CDV was constructed by sequential cloning using the Onderstepoort vaccine strain large-plaque-forming variant. The presence of a T7 promoter allowed transcription of full-length antigenomic RNA by a T7 RNA polymerase, which was provided by a host range mutant of vaccinia virus (MVA-T7). Plasmids expressing the nucleocapsid protein, the phosphoprotein, and the viral RNA-dependent RNA polymerase, also under control of a T7 promoter, have been generated. Infection of HeLa cells with MVA-T7 and subsequent transfection of p(+)CDV plus the helper plasmids led to syncytium formation and release of infectious recombinant (r) CDV. Comparison of the rescued virus with the parental virus revealed no major differences in the progression of infection or in the shape and size of syncytia. A genetic tag, consisting of two nucleotide changes within the coding region of the L protein, has been identified in the rCDV genome. Expression by rCDV of all the major viral structural proteins has been demonstrated by immunofluorescence.
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PMID:Establishment of a rescue system for canine distemper virus. 1104 18

Chagas' disease, caused by the parasite Trypanosoma cruzi, is an important cause of heart disease. Previous studies from this laboratory revealed that microvascular spasm and myocardial ischemia were observed in infected mice. Infection of endothelial cells with this parasite increased the synthesis of biologically active endothelin-1 (ET-1). Therefore. in the myocardium of T. cruzi-infected mice, we examined ET-1 expression and the p42/44-mitogen activated protein kinase (MAPK)-AP-1 pathway that regulates the expression of ET-1. There was parasitism and myonecrosis in the myocardium of infected C57BL/6 mice. Reverse transcriptase polymerase chain reaction (RT-PCR) analysis revealed elevated mRNA expression of transcription factor AP-1 (c-jun and c-fos) and increased AP-1 DNA binding activity as determined by electrophoretic mobility shift assay (EMSA). Western blot analysis demonstrated an increase in the phosphorylated forms of extracellular signal-regulated kinase (ERK1/2). ET-1 mRNA was upregulated in the myocardium of infected mice. Immunohistochemical and immunoelectron microscopy using anti-ET-1 antibody detected increased expression in cardiac myocytes and endothelium of these mice. These data suggest that ET-1 contributes to chagasic cardiomyopathy and that the mechanism of the increased expression of ET-1 is a result of the activation of the MAPK pathway by T. cruzi infection.
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PMID:Trypanosoma cruzi infection (Chagas' disease) of mice causes activation of the mitogen-activated protein kinase cascade and expression of endothelin-1 in the myocardium. 1107 62

The hepatitis C viruses (HCVs) are a group of small enveloped RNA viruses that have been viewed as a leading cause of chronic hepatitis in humans. Infections by HCV represent a serious global health problem, because millions of people worldwide are infected and no efficient treatment is available at the present time. Since HCV was identified in 1989, considerable effort has been devoted to the discovery and development of novel molecules to treat HCV-related diseases. One of the approaches is the development of novel inhibitors that interrupt the normal functions of HCV NS5B, an RNA-dependent RNA polymerase essential to HCV replication. This review summarizes recent advances in the biochemical and structural understanding of HCV NS5B polymerase as well as in the development of antiviral agents targeting this important enzyme.
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PMID:RNA-dependent RNA polymerase encoded by hepatitis C virus: biomedical applications. 1216 21

The 2 groups of human coronaviruses (HCoVs) represented by the prototype strains HCoV 229E and HCoV OC43 are mostly known as viruses responsible for common cold syndrome. HCoVs are difficult to detect, and epidemiological data are rare. From October 2000 through April 2001, we tested 1803 respiratory samples for HCoV by reverse-transcriptase polymerase chain reaction. From 8 February through 27 March 2001, HCoV OC43 was detected in samples obtained from 30 (6%) of 501 patients. The other viruses detected were respiratory syncytial virus (6.1%), parainfluenza virus 3 (1%), influenza virus A (7.8%), influenza virus B (7.2%), rhinovirus (6.4%), enterovirus (1%), and adenovirus (2%). Infection with HCoV OC43 was detected in patients of all age groups. The following clinical symptoms were noted: fever (in 59.8% of patients), general symptoms (in 30%), digestive problems (in 56.8%), rhinitis (in 36.6%), pharyngitis (in 30%), laryngitis (in 3.3%), otitis (in 13.3%), bronchitis (in 16.6%), bronchiolitis (in 10%), and pneumonia (in 6.6%). This study shows that an outbreak of HCoV OC43 respiratory infection was responsible for the lower respiratory tract symptoms observed in nearly one-third of patients identified by active surveillance for coronavirus infection.
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PMID:An outbreak of coronavirus OC43 respiratory infection in Normandy, France. 1268 10


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