Characterization of Early Region 1 and pIX of Bovine Adenovirus-3

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The mRNAs from early region 1 (E1) and pIX of bovine adenovirus type 3 (BAV-3) have been studied by Northern blot, S1 nuclease, and cDNA analysis and transcriptional maps for the regions were constructed. The transcriptional map for the E1 region of BAV-3 is different from those of mouse and human adenoviruses for which transcriptional maps for the regions have been constructed. The E1A region of BAV-3 is located between 0.8 and 10.5 map units and several different transcripts are produced from the region using alternative splice donor sites. The transcripts from the E1A region overlap with those of E1B and pIX. In BAV-3, the E1B region maps between 4.2 and 10.5 map units and encodes two major mRNA species. The mRNAs of E1B region differ from each other in that the smaller mRNA coding for the 157R protein has a large intron removed from a region corresponding to the coding region of E1B 420R protein. As in HAVs, the E1B 420R protein of BAV-3 could be translated only by internal initiation from the larger bicistronic mRNA as there are no transcripts produced exclusively for the production of 420R protein. The transcriptional unit of pIX is transcribed from an independent promoter and encodes a structural component of the adenovirus capsid. To identify and characterize the proteins produced from the region, antibodies were raised in rabbits that recognized specific proteins in Western blot and immunoprecipitation assays.