Comparative aspects of the replication of alphaviruses and poliovirus

The replication of both alpha- and picornaviruses results in the production of plus-stranded viral progeny. Each of these two classes of virus devotes about the same amount of viral genetic information to structural proteins but the alphaviruses use more genetic information for non-virion proteins. This additional information may be required because the alphaviruses have a much broader host range. Alternatively, the additional information may be required for interrupted transcription that yields a subgenomic mRNA that encodes all of the alphaviral structural proteins. This subgenomic mRNA allows preferential synthesis of a precursor af all virion proteins. Cleavage of this precursor has been observed during in vitro protein synthesis and can be prevented by an appropriate temperature-sensitive mutation.