Regulation of Viral Transcription Units by SV40 T-Antigen

Abstract

We have investigated the ability of SV40 T-antigen to trans-activate the SV40 late and the Adenovirus E2 promoters. Transcriptional control signals required for T-antigen trans-activation of the SV40 late promoter include T-antigen binding site II and the SV40 72-bp repeats. In vivo competition with recombinant plasmids containing the entire SV40 late regulatory region and promoter sequences (mp 5171–272) results in quantitative removal of limiting trans-acting factors required for late gene expression in COS-1 cells. Insertion of increasing lengths of DNA sequences between the T-antigen binding sites and the 72-bp repeats dramatically reduces the competition efficiency, suggesting a physical interaction between proteins binding to the separate regulatory domains. Transfection experiments have been performed in ts2 COS cells, which express the ts 1609 SV40 T-antigen. Transfection at the non-permissive temperature (40°C) resulted in a 5- to 10-fold reduction in SV40 late promoter activity compared to the permissive temperature (33°C), suggesting that trans-activation of the SV40 late promoter requires continued expression of T-antigen.