Protein Synthesis in HeLa Cells Double-infected with Encephalomyocarditis Virus and Poliovirus

Abstract

SUMMARYThe pattern of host, encephalomyocarditis (EMC) virus and poliovirus protein synthesis in HeLa cells double-infected with EMC virus and poliovirus has been examined. Both picornaviruses were able to block host translation after infection, although with different degrees of efficiency. In co-infection experiments, the inhibition of poliovirus protein synthesis by EMC virus and vice versa depended on the relative multiplicities of infection of each virus used. Under some conditions, double-infected HeLa cells simultaneously synthesized poliovirus and EMC virus proteins. In superinfection experiments, when the two viruses were added at different times, the pattern of the proteins synthesized depended on the time of addition of the second virus challenge. Poliovirus did not replicate when added 4 h after EMC virus. On the other hand, EMC virus replication was inhibited in cells preinfected with poliovirus. If co-infected cells were treated with guanidine from the beginning of the infection, only the synthesis of EMC virus proteins was apparent. However, if poliovirus was allowed to replicate for 4 h before guanidine addition, then the synthesis of EMC virus proteins was reduced, even though the translation of poliovirus mRNA was very much inhibited. EMC virus-infected HeLa cells exclusively synthesized cellular proteins in hypotonic media, whereas under hypertonic conditions only virus protein synthesis took place. In poliovirus-infected HeLa cells no cellular translation was detected under all ionic conditions tested. The ionic optimum of EMC virus and poliovirus protein synthesis was also different in cells infected with a single virus. However, in double-infected cells the monovalent ion optimum for translation of EMC virus and poliovirus mRNA was the same, although EMC virus protein synthesis was more resistant to inhibition by hypertonic media. No cellular protein synthesis was detected in double-infected HeLa cells under all the ionic conditions tested.

Effects of Poliovirus 2Apro on Vaccinia Virus Gene Expression

“…DitTerential inhibition by poliovirus ZAP'" of vaccinia virus expression and poliovirus protein 2C production. Translation of poliovirus mRNA occurs after p23-0 cleavage in infected cells (Sonenberg, 1990) and translation or poliovirus and encephalomiocarditis vinis (EMC) virus mRNhs occurs in doubly infected cells (Alonso and Carrasco, 1982). Thcse results indicate that inract p220 is not necessary for internal translational initiation of these mRNAs. '…”

Regulation of Protein Synthesis in Virus-Infected Animal Cells

“…Carrasco has suggested that the increased permeability of virusinfected cells to monovalent cations might mediate the switch from host to viral translation (Carrasco and Lacal, 1983;Carrasco and Smith, 1976). When infected cells are incubated in medium containing sufficient excess NaCl to inhibit the translation of most other proteins, poliovirus translation is fairly resistant (Alonso and Carrasco, 1982a;Nuss et al, 19751, but the resistance is not as striking as with EMC virus (Alonso and Carrasco, 1982b). The stimulation of in uitro translation by high salt is also less obvious with poliovirus mRNA than with some other picornaviruses (Bossart and Bienz, 1981).…”

“…In the natural course of infection by poliovirus, the precipitous decline in host translation occurs within the first 2 hours, prior to the observed increase in intracellular sodium ions (Nair et al, 1979). Moreover, the synthesis of cellular proteins cannot be reactivated by incubating poliovirusinfected cells in hypotonic medium (Alonso and Carrasco, 1982b), a manipulation that works beautifully with EMC virus. Thus, hypertonicity does not appear to underlie the shutoff of host protein synthesis by poliovirus.…”

Action of brefeldin A on translation in Semliki Forest virus-infected HeLa cells and cells doubly infected with poliovirus

“…Even the translation of another picornavirus RNA, such as EMCV RNA, is efficiently blocked by poliovirus when similar multiplicities of infection are used (Alonso & Carrasco, 1982b), indicating that the poliovirus-induced inhibition L. Pgrez, A. Irurzun and L. Carrasco of EMCV mRNA translation is possibly not mediated by the blockage of cap recognition factors. Under some conditions, particularly when low poliovirus m.o.i.s are used, translation of other viral mRNAs, including capped mRNAs, occurs in poliovirus-infected cells (Schrader & Westaway, 1990;Mufioz et al, 1984Mufioz et al, , 1985Alonso & Carrasco, 1982a).…”