Sequence and transcription map analysis of early region-1 of porcine adenovirus type-3

Abstract

The nucleotide sequence of a region of the genome of porcine adenovirus-3 (PAV-3) between map units 1 and 12.2 was determined. The sequenced region included four major open reading frames, and several transcription control elements. Homology studies, using the deduced amino acid sequences of the open reading frames, revealed genes coding for the E1A, E1B 202R, E1B 474R and pIX proteins. The region was characterized by Northern blot analysis and sequencing of cDNA clones. In PAV-3, the E1A region is located between 1.5 and 3.8 map units. Alternate splice donor sites are used to produce four different types of transcripts from the primary transcript of the E1A region. The E1A proteins of PAV-3 contain a consensus zinc finger motif, which was shown to be the principal transactivation region of human adenovirus-5 (HAV-5) E1A proteins. The PAV-3 E1A proteins also contain a retinoblastoma susceptibility protein (pRb) binding motif, which in HAVs interacts with cellular Rb protein to overcome the pRb mediated transcription repression. The E1B region in PAV-3 maps between 4.0 and 12.2 map units, and shares a polyadenylation signal and polyadenylation sites with the gene coding for pIX. A single major and a number of minor mRNA species are produced from the E1B region. The open reading frame (ORF) analysis of cDNA representing major mRNA produced from the E1B region showed two overlapping ORFs corresponding to 19K and 55K ORFs of HAV-2. In PAV-3, the gene coding for pIX is located between 9.9 and 12.2 map units and codes for a protein of 199 amino acids.