RNA, poliovirus-induced

G. Koch Table 2. Biological and physicochemical properties of poliovirus-induced RNAs ... 

Arildone (17) is a 6-diketone which has broad-spectrum activity against several important DNA and RNA viral pathogens. >2 An isoxazole analog, WIN 49321 (18), has recently been reported to have antipicornavirus activity. The isoxazole 18 Inhibited plaque formation by 24 of 27 human rhinovirus serotypes, poliovirus and Echovirus by 50% at concentrations ranging from 0.03 to 15 pM. It was orally effective in protecting mice against poliovirus-Induced death in a dose-dependent... 

Gliotoxin (308) is a fungal metabolite, isolated from Aspergillus terreus and found to have antibacterial, antitumor and antifungal effects [18]. Gliotoxin acetate inhibited the CPE of poliovirus in monkey kidney cell cultures due to the early stage inhibition of RNA viral replication [18]. Gliotoxin also inhibits influenza virus-induced RNA polymerase. 

Black TL, Barber GN, Katze MG. Degradation of the interferon-induced 68,000-M(r) protein kinase by poliovirus requires RNA. J Virol 1993 67(2) 79T800. 

The suggestion that viral mRNA is an inherently efficient mRNA and can effectively compete with cellular mRNAs for some limiting component of the protein-synthesizing machinery has acquired experimental support for picornaviruses other than polioviruses. A direct competition model for shut-off of host cell translation has been proposed, specifically, to describe the shut-off induced by the car-dioviruses, EMC, and mengo (see Section 7, below). However, these models do not apply to poliovirus-induced inhibition because, as noted above, cessation of protein synthesis in poliovirus-infected cells occurs before detectable viral RNA is synthesized and shut-off does occur after infection in the presence of guanidine or with a mutant virus temperature-sensitive for RNA synthesis at restrictive temperature. 

A block at the level of initiation of protein synthesis has also been suggested as the mechanism of shut-off by vesicular stomatitis virus (VSV Stanners et al., 1977 Jaye et al., 1982 Gillies and Stollar, 1982). As in poliovirus-induced shut-off, degradation of host mRNAs does not seem to play a role in VSV-induced shut-off since host mRNA can be extracted from infected cells and translated in vitro (Ehrenfeld and Lund, 1977). However, recent work has demonstrated that the synthesis of VSV leader RNA is directly related to inhibition of host RNA synthesis (Grinnell and Wagner, 1983). Unlike poliovirus mRNAs, VSV mRNAs are capped and require cap-binding protein for translation (Banerjee, 1980 Rose et al., 1978). The mechanism of VSV-induced shut-off is presently under active investigation to determine if competition between mRNAs (Lodish and Porter, 1980,... 

Fig. 18. Analysis of RF-RNA by gradient centrifugation. The RF-RNA fraction isolated from E. coli after 15 minutes incubation at 37° C following exposure to p.iabeled (a) or i C-labeled (b) poliovirus-induced RF-RNA (less than 1 pg/l g of E. coli see Table 11) was analyzed by density gradient centrifugation (a) and by zonal centrifugation (b).

Bishop, J. M., Koch, G. Purification and characterization of poliovirus induced infectious double-stranded RNA. Biol. Chem. 242, 1736 (1967). 

Lempidakis, G. A., Koch, G. Interaction of viral RNA with E. coli. I. Polycation augmented adsorption of poliovirus induced double-stranded RNA. Arch. Biochem. Biophys. (1972) (in press). 

Mittelstaedt, R., Koch, G. Poliovirus induced infectious double-stranded RNA Effect of RNA degrading enzymes (to be published in 1974). 

Poliovirus noncapsid protein 3A is a multifunctional viral protein involved in poliovirus RNA replication. One of its functions is suppression of protein trafficking between the ER and Golgi apparatus. In infected cells, it affects the intracellular trafficking of TNFR and induces TNF resistance by eliminating TNFRs from the plasma membrane. This 3A-protein-mediated inhibition of ER to Golgi traffic ofTNFR was limited to poliovirus and coxsackievirus B3. Further investigation is required to understand whether this inhibition is selective for TNFR or not. 

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 ... 

Bablanian et al., 1965, Penman and Summers, 1965). Last, infection with a temperature-sensitive mutant of poliovirus that synthesizes no single-stranded RNA at restrictive temperature nevertheless induces normal inhibition of cellular protein synthesis (Hewlett et al., 1982). All of these results argue against a competition between cellular and viral mRNAs for cellular components as an explanation for the selective inhibition of cellular protein synthesis. A large body of experimental work on this subject has been performed with poliovirus-infected cells, and consequently, the major focus of this review is on the inhibiton of protein synthesis by poliovirus. 

An alternative type of explanation for the specific discrimination against host cell protein synthesis in poliovirus-infected cells stemmed from the observation that initiation of protein synthesis could be selectively inhibited in HeLa cells and in poliovirus-infected HeLa cells by increasing the osmolarity of the growth medium (Sa-borio et al., 1974). The inhibition was independent of the solute used to increase the osmolarity. However, virus-directed protein synthesis was observed to be relatively more resistant to inhibition by hypertonic medium than was cellular protein synthesis, a fact which was interpreted as indicating that initiation of viral RNA translation was intrinsically more efficient than that of cellular mRNA (Nuss et al., 1975). These workers, therefore, proposed that the virus-specific or virus-induced factor involved in suppression of host protein synthesis could function by indiscriminantly lowering the rate of peptide chain initiation. Under such conditions, translation of viral mRNA, when it was synthesized, could occur due to its inherently strong affinity... 

Double-stranded RNA (dsRNA) has been implicated in picor-navirus-induced shut-off (Ehrenfeld and Hunt, 1971) however, the inhibition of protein synthesis caused by poliovirus double-stranded RNA is nondiscriminatory with respect to host or viral mRNAs (Celma and Ehrenfeld, 1974). Double-stranded RNA is obtained during extraction of RNA from infected cells and can also be found in in vitro transcription. It has been proposed that this dsRNA is produced by vaccinia virus both in vivo (Duesberg and Colby, 1969) and in vitro (Colby et al., 1971) as a result of symmetrical transcription. The role of vaccinia virus double-stranded RNA in shut-off has been investigated. To determine the relation of in v/vo-synthesized vaccinia virus-induced double-stranded RNA to shut-off, we measured the percentage and amount of double-strand RNA formed in infected L929 cells treated with cycloheximide conditions where severe inhibition occurs and a large amount of viral RNA is produced (Schrom... 

These data suggest that the alphavirus-induced inhibition of host cell RNA synthesis occurs at the transcriptional level. To test this possibility, the cell-free transcription system (Manley et al., 1980) which has been developed for studying an inhibitory factor present in poliovirus-infected cells (Baron and Baltimore, 1982) would be useful. With such a system, it would be possible to determine whether inhibitory factor(s) are induced in alphavirus-infected cells or whether the inhibition results from a competition for the available pool of RNA precursors. The genetic approach is not possible at this time since no conditional lethal alphavirus mutant has been described which affects the regulation of host cell RNA synthesis. 

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