Strand orientation of simian virus 40 transcription in productively infected cells.

Strand orientation of transcription in BSC-1 cells infected by simian virus 40 (SV40) was investigated by annealing RNAs extracted from infected cells with asymmetric complementary RNA from SV40 DNA synthesized in vitro by RNA polymerase from Escherichia coli. The results suggest that the early viral RNA sequences (those made before replication of viral DNA) and the late RNA sequences (those synthesized concurrently with replication of viral DNA) are transcribed from opposite strands of the SV40 DNA. The RNA synthesized in vitro is of the same polarity as the early in vivo RNA and is complementary to the late in vivo RNA. Knowledge of strand selection in lytic infection is a step towards understanding the regulation of transcription of this viral DNA.