The expression of the SV40 early region in the transformed human cell line SV80

The one complete copy of the SV40 early region present in human cells of the transformed line SV80 carries a duplication of the 5' portion of the early region, including its transcriptional control region and splicing signals (W. Gish and M. Botchan, personal communication). Novel SV40-specific RNA species of sufficiently large size, 3.8 and 4.2 kb, to be expressed from the duplicated early transcriptional control region were detected in SV80 cytoplasmic and nuclear RNA preparations by blot hybridization. The results of transcription in a cell-free system of a plasmid, pSV80-04, representing this SV80 cell SV40 DNA integrate (W. Gish and M. Botchan, personal communication) and of nuclease protection experiments with end-labelled pSV80-04 DNA fragments support the conclusion that the duplicated early sequences are transcribed in SV80 cells. It has also been established that the duplicated early splicing signals are functional in SV80 cells. These results are discussed in relation to the large amounts of SV40 early mRNA and T-antigen synthesized in cells of the SV80 line.