Bovine adenovirus-3 E1A coding region contain cis-acting DNA packaging motifs

To elucidate further the regulation of E1 gene transcription and viral DNA packaging, we constructed and analyzed mutant BAdV-3s in which the deletion of sequences between left ITR and E1A ATG codon was combined with the functional blocking of E1A gene expression by introducing deletion mutations into E1A open reading frame (ORF). The results suggest that E1A coding region contains cis-acting packaging motifs for efficient encapsidation of BAdV-3 DNA into preformed empty capsids. In addition, E1A is not required for the transcription of E1B.