Protein synthesis Processing, Virus-Induced

Infection of cultured cells with many lytic viruses results in a marked decrease in the rate of cellular protein synthesis. Usually, this decrease is accompanied by increasing rates of viral protein synthesis, marked cytopathic effects, and ultimately cell death. In most cases, it is not known whether the shut-off of host cell protein synthesis results from an active process induced by the virus evolved for that (or some other) purpose, or whether it is merely a passive result of another viral function, such as production of large quantities of viral mRNA which compete effectively with their cellular counterparts. In the case of poliovirus, however, three types of studies suggested that the former, active type of mechanism was at work. Kinetic analysis of the rate of protein synthesis in cells synchronously infected with high multiplicities of virus showed that cellular protein synthesis could be virtually completely inhibited prior to the synthesis of significant quantities of viral RNA and protein (Summers et ai, 1965). In addition, infection in the presence of 1-3 mM guanidine, which prevents detectable replication of viral RNA, nevertheless results in viral inhibition of host cell protein synthesis (Holland, 1%4 ... 

If none of the normal processing reactions that modify a pre-mRNA chain are inhibited by adenovirus infection, then it would seem that the virus must induce either selective transport of viral mRNA or a mechanism that discriminates among viral and cellular species at some prior step, upon which transport itself depends. Examples of the latter class of mechanism might include incomplete or incorrect packaging of cellular transcripts with nuclear proteins for form hnRNP or the displacement of cellular RNA molecules from their normal site(s) of synthesis or processing within the nucleus (for example, attached to a structure such as the nuclear matrix Herman et al., 1978 Miller et al., 1978 van Eekelen and van Venrooij, 1981 Jackson et al., 1981, 1982 Maniman et al., 1982.). Experimental evidence that addresses either of these possibilities directly is not available. It does, however, seem clear that hnRNP populations isolated from adenovirus-infected cells do not comprise solely viral RNA se-... 

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