121R protein from the E3 region of bovine adenovirus-3 inhibits cytolysis of mouse cells by human tumor necrosis factor

Based on the DNA sequence and known mRNA structures, the early region 3 (E3 ) of bovine adenovirus (BAV)-3 has the potential to encode four proteins. O ne of them (121R) is produced as a 14.5-kD protein throughout infection. An alysis of the 121R protein showed limited homology to a 14.7K protein of hu man adenovirus (HAV)-5. Interestingly, both anti-14.7K and anti-121R sera i mmunoprecipitated a 14.5-kD protein from cells infected with BAV-3. To dete rmine if 121R is functionally related to 14.7K, we constructed a recombinan t E3-deleted HAV-5 (AdKV121) expressing the BAV-3 E3 121R protein. Mouse C3 HA cells infected with HAV-5 mutant dl 758 (deletion of 14.7K) were sensiti ve to TNF lysis. However, wild-type HAV-5- or recombinant AdKV121-infected cells were resistant to TNF-induced cytolysis. Our result show that the BAV -3 E3 121R protein is serologically and functionally related to the 14.7K p rotein encoded by the E3 region of HAV-5. Copyright (C) 2001 S. Karger AG, Basel.