Sequence analysis of the putative E3 region of bovine adenovirus type 2.

Adenoviruses are nonenveloped icosahedral-shaped particles. The double-stranded viral DNA genome contains four major early transcription units, designated E1 (a and b), E2 (a and b), E3 and E4, which are expressed in a regulated manner soon after infection. The gene products of the region E3, shown to be nonessential for viral replication in vitro, are believed to be involved in counteracting host immunosurveillance. Human adenovirus type 5 DNA sequences of transcription units L4 and L5 adjacent to E3 were used to localize E3 within the bovine adenovirus type 2. The DNA sequences between 74.8 and 84.4 mu containing E3 and the fiber gene were determined. The E3 region was found to consist of about 2.3 kb pairs and to encode four proteins longer than 60 amino acids. However, these four open reading frames did not show significant homology to any other known adenovirus DNA or protein sequence.