The E4 transcriptional unit of Ad2: far upstream sequences are required for its transactivation by E1A

We have investigated the effect of the E1A polypeptides of adenovirus 2 on the transcription of the viral E4 region. For this purpose, we have fused the promoter region of the E4 gene to the bacterial gene coding for chloramphenicol acetyl transferase. We have found that transcription from the E4 promoter is increased at least 20 fold in the presence of the E1A region. We have also found that the largest E1A polypeptide is the regulating factor, whereas the shortest has no apparent effect. Deletion of sequences upstream from position -158, as measured from the cap site, reduces the efficiency of the transcription in the presence of E1A by more than 15 fold. An important regulatory domain lies between positions -158 and -179. This domain contains the sequence 5' GGGAAGTGAC 3' which is homologous to the E1A enhancer core sequence. Another similar sequence is also present at position -149.