SV40 gene activity during lytic infection and in a series of SV40 transformed mouse cells.

Transcription of SV40 DNA was measured during lytic infection and in five SV40 transformed mouse cell lines. During productive infection, 50 per cent of viral DNA reacted with saturating amounts of lytic RNA. Varying portions of the SV40 genome were transcribed in transformed mouse cells, ranging from 15 per cent in a line which failed to yield virus, to 50 per cent in one line from which high titers of virus were obtained following cell fusion. The RNA from the SV40 transformed cell line, which saturated 50 per cent of the viral DNA, could not be distinguished from SV40 lytic RNA in reciprocal competition-hybridization experiments. These results suggest that some block or defect, subsequent to the transcription of SV40 DNA, prevents the appearance of progeny virus in this transformed 3T3 cell.