The 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.

Keyword(s): ions , picornavirus , shut-off and translation

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