E1A promoter of bovine adenovirus type 3

Conserved motifs of eukaryotic gene promoters, such as TATA box and CAAT box sequences, of E1A of human adenoviruses (e.g human adenovirus 5) lie between the left inverted terminal repeat (ITR) and the ATG of E1A. However, analysis of the left end of the bovine adenovirus 3 (BAdV-3) genome revealed that the conserved sequences of the E1A promoter are present only in the ITR. As such, the promoter activity of ITR was tested in the context of a BAdV-3 vector or a plasmid-based system. Different regions of the left end of the BAdV-3 genome initiated transcription of the red fluorescent protein gene in a plasmid-based system. Moreover, BAdV-3 mutants in which the open reading frame of E1A was placed immediately downstream of the ITR produced E1A transcript and could be propagated in non-E1A-complementing Madin–Darby bovine kidney cells. These results suggest that the left ITR contains the sole BAdV-3 E1A promoter.