Expression of the poliovirus genome from infectious cDNA is dependent upon arrangements of eukaryotic and prokaryotic sequences in recombinant plasmids.

The introduction of a cDNA copy of poliovirus type 1 (Mahoney) into cultured primate cells results in the production of infectious virus. The level of infectious virus can be increased by incorporation of eukaryotic signals of transcription and replication. We have utilized the SV40 DNA sequence coding for the early and late promoters, the SV40 origin of replication, and the enhancer elements, along with the cDNA of poliovirus, to determine the important parameters for the level of infectious virus produced following transfection. Although plasmid replication increases the level of infectivity, the major determinant of infectivity is promoter activity.