Inhibition by interferon of SV40 tumor antigen formation in cells injected with SV40 cRNA transcribed in vitro

The interferons exert their action on the replication of viruses by inhibition of the viral genome expression. The target viral genome function inhibited was shown for two RNA viruses to be primarily the viral genome transcription (vesicular stomatitis virus [ 1, 21, reovirus [ 31). In the case of other viruses the viral genome translation is primarily affected by interferon (e.g. arbovirus [ 41, encephalomyocarditis virus [ 51, vaccmia virus [6]). Concerning the DNA-containing simian virus (SV40), it was found that in monkey cells both the viral transcription and viral translation were reduced by the same rate by human interferon [7] . These findings support the hypothesis that the SV40 genome transcription is primarily affected by interferon. However with polyinosinic:polytidylic acid as an interferon inducing agent we had found that the viral translation (formation of tumor antigen) is inhibited by 99% or higher, whereas the formation of early viral RNA was reduced only to 20% [8,9]. These findings support the hypothesis that translation rather than transcription of SV40 genome is inhibited by interferon. In order to get further information whether interferon inhibits SV40 genome expression mainly at the