Structure and function of the S1 nuclease-sensitive site in the adenovirus late promoter.

We analyzed an S1 nuclease-sensitive site present in supercoiled, but not linear, recombinant plasmids containing the adenovirus late promoter. S1 nicking was detected on both strands, primarily in the TATA box. Analysis of deletion mutants showed that sequences upstream of -47 and downstream of -12 are not required for S1 cutting. However, a number of different base substitution mutations in stretches of G residues upstream and/or downstream of the TATA box were sufficient to eliminate S1 cutting. When the transcriptional activities of these mutant promoters were assayed in vivo, six of seven mutants lacking the ability to form the S1-sensitive structure showed no reduction in transcriptional potential. In fact, several showed increased promoter activities. These data show that the S1 nuclease cutting site in the adenovirus late promoter has precise nucleotide sequence requirements for its formation. However, the ability of recombinant plasmids to adapt this conformation in vitro is not necessary for such plasmids to serve as templates for transcription in vivo.