RNA synthesis virus

Cowton VM, McGivem DR, Feams R (2006) Unravelling the complexities of respiratory syncytial virus RNA synthesis. J Gen Virol 87 1805-1821... 

H) 2 5 oligo(A) synthesized. Encephalomyocarditis virus RNA synthesis was measured by incubation with (5h) uridine in cells treated with interferon as indicated above 5 hr after infection actinomycin D was added to 5 p,g/ml for 10 min and the cells were incubated with (5h) uridine for JO min as previously described (21). The inhibition of viral ENA synthesis in interferon-treated cells relative to control infected cells is indicated (x---x). 

Nucleosides containing a carbon ribose linkage from fermentations such as formycin, showdomycin, and pyrazomycin, are of interest as a potential type of metabolically stabilized antivirals. Formycin inhibits the growth of a wide spectrum of DNA and RNA viruses. In Vero cells infected with Japanese encephalitis virus, RNA synthesis was markedly... 

Marcus, P. I., Engelhardt, D. L., Hunt, J. M., and Sekellick, M. J., 1971, Interferon action. Inhibition of vesicular stomatitis virus RNA synthesis induced by virion-bound polymerases, Science 174 593. 

Watson, R. J., and Clements, J. B., 1980, A herpes simplex type 1 function continuously required for early and late virus RNA synthesis. Nature London) 285 329. 

However, the volume of information inscribed in 1200 nucleotides is insufficient for spontaneous propagation of the virus in plant cells, and it can reproduce only as the satellite of another virus—virus of tobacco necrosis, possessing RNA with a molecular wei t of 2 X 10. Proteins of these viruses are serologically different, but the basic virus evidently enables certain factors to be synthesized which are equally essential for the formation of both viruses. RNA synthesis in the host cells takes place on DNA templates and is catalyzed by DNA-dependent RNA-polymerase. It may be assumed that a special factor—the enzyme RNA-replicase— which is not used for reproduction of the satellite virus is essential for synthesis of virus RNA on RNA templates (autoreplication of RNA). 

Just as withplant viruses, RNA synthesis by certain animal viruses takes place in the cytoplasm, and by others in the nucleus synthesis of virus proteins, however, takes place only in the cytoplasm, on the ribosomes (polysomes). 

Stuyver LJ, McBrayer TR, Tharnish PM, Clark J, Hollecker L, Lostia S, Nachman T, Grier J, Bennett MA, Xie MY, Schinazi RF, Morrey JD, Inlander JL, Furman PA, Otto MJ (2006a) Inhibition of hepatitis C replicon RNA synthesis by beta-D-2 -deoxy-2 -fluoro-2 -C-methylcytidine a specific inhibitor of hepatitis C virus replication, Antivir Chem Chemother 17 79-87... 

Zhong W, Uss AS, Ferrari E, Lau JY, Hong Z (2000) De novo initiation of RNA synthesis by hepatitis C virus nonstructural protein 5B polymerase. J Virol 74 2017-2022 Zhou S, Yung Chan S, Cher Goh B, Chan E, Duan W, Huang M, McLeod HL (2005) Mechanism-based inhibition of cytochrome P450 3A4 by therapeutic drugs. Clin Pharma-cokinet 44 279-304... 

As noted, the viral RNA is of the plus (+) sense. Replicase synthesizes RNA of minus (-) sense using the infecting RNA as template. After minus RNA has been synthesized, plus RNA is made from this minus RNA. The newly made plus RNA strands now serve as messengers for virus protein synthesis. The gene for the maturation protein is at the 5 end of the RNA. Translation of the gene coding for the maturation protein (needed in only one copy per virus particle), occurs only from the newly formed plus-strand RNA as... 

This dilemma could be overcome by the hypercycle model hypercycles are in fact not theoretical concepts, but can be observed (in a simple form) in today s organisms, where an RNA virus transfers the information for an enzyme in the host cell, which is able to carry out the preferred synthesis of new virus RNA. This RNA synthesis is supported by host factors, and an RNA minus-strand is formed. The following RNA replication affords a plus-strand. The process corresponds to a double feedback loop and involves the enzyme coded by the RNA matrix and the information present in the matrix in the form of a nucleotide sequence. Both factors contribute to the replication of the matrix, so that there is second-order autocatalysis (Eigen et al., 1982). 

Mechanism of Action A synthetic nucleoside that inhibits influenza virus RNA polymerase activity and interferes with expression of messenger RNA. Therapeutic Effect Inhibits viral protein synthesis and replication of viral RNA and DNA. Pharmacokinetics Rapidly absorbed from the GI tract following oral administration. A small amount is systemically absorbed following inhalation. Primarily excreted in urine. Half-life 298 hr (oral) 9.5 hr (inhalation). 

In our discussion of DNA and RNA synthesis up to this point, the role of the template strand has been reserved for DNA. However, some enzymes use an RNA template for nucleic acid synthesis. With the very important exception of viruses with an RNA genome, these enzymes play only a modest role in information pathways. RNA viruses are the source of most RNA-dependent polymerases characterized so far. 

In addition, they assist in replication of RNA viruses, another process that requires RNA synthesis. Viruses sometimes make use of host RNA polymerases but often synthesize their own catalytic subunits. Bacteriophage T4 uses the E. coli RNA polymerase and o factors but modifies their action through the binding of several phage-encoded proteins.248 In contrast, phage T7 encodes its own relatively simple RNAP whose initiation complex (Section A,2)29 and elongation complexes have been studied 249-249b... 

Many Viruses Encode Their Own RNA Polymerases RNA-Dependent RNA Polymerases of RNA Viruses Other Types of RNA Synthesis Posttranscriptional Alterations of Transcripts... 

Talib, S., and J.E. Hearst. 1983. Initiation of RNA synthesis in vitro by vesicular stomatitis virus Single internal initiation in the presence of aurintricarboxylic acid and vanadyl ribonucleoside complexes. Nucleic Acids Res 11 7031. 

In addition to the antineoplastic activity, camptothecin was found to be an effective inhibitor of adenovirus replication [268, 269] and herpes virus replication [252, 270]. 10-Methoxycamptothecin is about 8-times more potent than camptothecin as an inhibitor of herpes virus [252]. A combination of camptothecin and dimethyl sulphoxide is very effective for the topical treatment of psoriasis [271]. Since, in the goldfish brain, camptothecin blocks RNA synthesis in eucaryotic cells by blocking the incorporation of uridine into RNA, this alkaloid can block the memory of conditioned avoidance and produces no measurable effect on retention of the learned response [272]. 

Most studies about the effects of ansamycins on DNA viruses have been made with vaccinia virus51l It has been found that some derivatives, such as rifampicin, inhibit the growth of this virus. There is no doubt, however, that this inhibition is not due to a block in RNA synthesis, as was found in bacteria, but apparently the assembly... 

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