Transcription of the viral genome in cell lines transformed by simian virus 40. I. Mapping of virus-specific nuclear RNAs.

Mapping of virus-specific nuclear transcripts was carried out in three lines of rat cells transformed by SV40. Each of these cell lines contained a single copy of integrated viral DNA with identified regions adjacent to cell DNA (1). The main virus-specific nuclear transcript in all of these cell lines was shown to be complementary to the minus strand of the early region in SV40 genome. Each cell nucleus contained approximately 50 copies of these RNAs. Transcripts complementary to both strands of the late region in viral genome were also detectable in all of these cell lines. Its content varied depending on the cell line and was 20-50-fold less than that of the main virus-specific transcript. All the regions of integrated SV40 genome in isolated nuclei of transformed cells were equally sensitive to pancreatic DNase I treatment suggesting that the whole viral genome served as a template for RNA synthesis in these cell lines.