Virus protein, synthesis

Virus infection obviously upsets the regulatory mechanisms of the host, since there is a marked overproduction of nucleic acid and protein in the infected cell. In some cases, virus infection causes a complete shutdown of host macromolecular synthesis while in other cases host synthesis proceeds concurrently with virus synthesis. In either case, the regulation of virus synthesis is under the control of the virus rather than the host. There are several elements of this control which are similar to the host regulatory mechanisms, but there are also some uniquely viral regulatory mechanisms. We discuss various regulatory mechanisms when we consider the individual viruses later in this chapter. 

Keranen, S., and Ruohonen, L., 1983, Nonstructural proteins of Semliki Forest virus Synthesis, processing and stability in infected cells, J. Virol. 47 505. 

Increase in enzymic activity of the infected cell. An increase in enzymic activity of the infected cell is contrary to the observations recorded above, and, indeed, with the exception of an enhancement of deoxyribonuclease, the activities of the bacterial enzymes appear to remain constant after infection of E. coli with the T phages (225a,227,227a). Since the enzymes appear to retain activity after infection, this suggests that the virus interferes with the synthesis of new enzymes, as well as RNA and protein, perhaps by diverting energy and metabolites from normal synthetic pathways to pathways of virus synthesis. 

When N -labeled E. coli are infected with T6r+ bacteriophage, about 80% of the viral N is derived from the medium and the other 20% comes from the bacterial cell (Kozloff, Knowlton, Putnam, and Evans, 160,163) the converse holds true when E. coli are infected with T7 (Putnam, Miller, Palm, and Evans, 262). Thus, the assimilation of virus N resembles that for virus P in that relatively more of the inorganic compounds of the medium are channeled into virus synthesis for the large phages than for the small ones. However, several important differences exist between N and P metabolism during phage multiplication (1) Analytically, P occurs almost wholly in the virus nucleic acid, whereas N is about equally divided between the nucleic acid and protein of the phage. Tracer... 

FIGURE 1.25 The virus life cycle. Viruses are mobile bits of genetic iuformatiou encapsulated in a protein coat. The genetic material can be either DNA or RNA. Once this genetic material gains entry to its host cell, it takes over the host machinery for macromolecular synthesis and subverts it to the synthesis of viral-specific nucleic acids and proteins. These virus components are then assembled into mature virus particles that are released from the cell. Often, this parasitic cycle of virus infection leads to cell death and disease. 

NUCLEOPROTEINS. Nucleoprotein conjugates have many roles in the storage and transmission of genetic information. Ribosomes are the sites of protein synthesis. Virus particles and even chromosomes are protein-nucleic acid complexes. 

The infectious cycle of a (+)-strand RNA virus such as the hepatitis C virus differs by the fate of the viral RNA genome in the infected cell. Upon entry into the cell, the HCV genome is used as a messenger RNA to drive the synthesis of a large polyprotein precursor of about 3,000 residues [2]. The structural proteins are excised from the precursor by host cell signal peptidase. 

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Apart from offering a new and highly specific approach to the inhibition of herpesviruses, this new mechanism of action could potentially also have beneficial immunological consequences. During treatment with BAY 38-4766, viral protein synthesis continues, but due to the lack of monomeric genomic length DNA, only empty particles (dense bodies) can be formed. It is conceivable that these non-infections viral particles could aid the establishment of an antiviral immune response, leading to better control of the virus by the host. This mechanism appears... 

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P] Halstrom, J., Kovdcs, K., Bninfeldt, K. Synthesis of the N-lVityl Hex ieplide Hydrazide Corresponding to the Sequence 152-157 of the Coat Protein of Tbbacco Mosaic Virus. Comparison of the Homogeneous and the Solid Phase Syntheses", Acta Chem. Scand. 1973, 27. 3085-3090. 

Many Viruses Co-opt the Host Cell Protein Synthesis Machinery... 

The protein synthesis machinery can also be modified in deleterious ways. Viruses replicate by using host... 

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