A novel eukaryotic promoter element: the simian virus 40 72 base pair repeat

Using both clones of mouse LMTK- cells cotransformed with various chimeric conalbumin promoter simian virus 40 (SV40) early gene recombinants and the herpes thymidine kinase gene, and HeLa cells transfected with the same chimeric recombinants, we show that the SV40 72 base pair (bp) repeat sequence is a bidirectional potentiator of initiation of transcription from adjacent T-A-T-A box-dependent and -independent start sites. These results are consistent with our previous model based mainly on the results of T antigen gene expression assays that the 72-bp repeat acts as a bidirectional entry site for RNA polymerase B. We also show that the conalbumin T-A-T-A box is an important element for efficient and accurate in vivo initiation of transcription.