Characterization of the early region 4 of porcine adenovirus type 3

The nucleotide sequence of a 3028 bp DNA segment, located between map co-ordinates 100 and 92 in the genome of porcine adenovirus type 3 (PAV-3), was determined. The segment includes the entire early region 4 (E-4) and the right inverted terminal repeat sequences. There were two TATA boxes and one canonical polyadenylation signal on the 1 strand. Homology searches of the GenBank data base for the predicted amino acid sequences revealed that, of the eight open reading frames (ORFs) on the 1 strand, and four ORFs on the r strand, only ORF 8 on the 1 strand showed homology with the 34 kDa E-4 protein of human adenovirus types 2, 12 and 34. Northern blot analysis showed that transcription from the E-4 region of PAV-3 began 4 h after infection, peaked at 8 h and declined after 10 h, before DNA replication began 16 h after infection. The E-4 region of PAV-3 was further characterized by 5' and 3' end mapping of the transcription unit.