Simian virus 40 (SV40) T-antigen transcriptional activation mediated through the Oct/SPH region of the SV40 late promoter.

Simian virus 40 (SV40) large T antigen is a promiscuous transcriptional activator of many viral and cellular promoters. The SV40 late promoter, a primary target for T-antigen transcriptional activation, contains a previously described T-antigen-activatable binding site (SV40 nucleotides 186 to 225). The T-antigen-activatable binding site element contains overlapping octamer (Oct)- and SPH (TEF-1)-binding sites (Oct/SPH site). Using this Oct/SPH site as an upstream element in a simple promoter, we show that the SPH sites are necessary for transcriptional activation by T antigen. In addition, we show that when Oct 1 is overproduced, it can eliminate T-antigen-mediated transcriptional activation, as well as basal activity, from the simple Oct/SPH promoter as well as the intact SV40 late promoter. This suggests that one function of T antigen in transcriptional activation of the late promoter is to alter factor binding at the Oct/SPH region to favor binding of factors to the SPH sites.