An enhancer-like element in the adenovirus E2 promoter contains sequences essential for uninduced and E1A-induced transcription.

Using a chloramphenicol acetyltransferase gene under the control of a series of adenovirus E2 promoter mutants, we have determined the sequence requirements for E1A-induced as well as uninduced expression of the E2 promoter. Fully induced expression requires 79 nucleotides of upstream sequence, and the same sequences are required for uninduced expression. A promoter containing 70 nucleotides of upstream sequence is inducible, although to a lower level than wild type, while a promoter containing 59 nucleotides of upstream sequence is not inducible. The sequences required for induction as well as for uninduced promoter activity map between 21 and 79 nucleotides upstream of the transcriptional initiation site and function in either orientation and at a distance. We suggest that E1A-mediated induction involves the effective increase in a factor utilizing this upstream site and that the factor can functionally interact with the site irrespective of its location relative to the start of transcription.