CHARACTERIZATION OF TUMOR-ANTIGENS IN CELLS TRANSFORMED BY FRAGMENTS OF ADENOVIRUS TYPE-5 DNA

The Ad5 T antigens in a number of transformed cell lines were isolated by immunoprecipitation with sera from hamsters bearing tumors induced by cells containing only Ad5 early region 1 (E1) DNA. The proteins were characterized by SDS-polyacrylamide gel electrophoresis. Major T antigens with molecular weights of 65K and 19K could be identified in cells transformed by virions or intact viral DNA. Minor species of 52K, 45K, 42-34K, 25K, 18K, 17K, 16K, and 15K were also found in variable amounts. Only a very limited number of anti-T sera from individual hamsters were able to precipitate all of these proteins; the majority precipitated the larger T antigens only. In particular, the 19K protein seemed weakly antigenic. Ad5 T antigens in primary rat kidney cells transformed with the following Ad5 DNA fragments were also analyzed: XhoI-C, BglII-D, HindIII-G, KpnI-H, and HpaI-E (comprising the left-most 15, 9.5, 8, 5.9, and 4.5% of the genome, respectively). The number of T antigens decreased with the size of the DNA fragment used for transformation. Cells transformed by the 15% fragment were similar to normal transformed cells, while all other cells lacked the major 65K T antigen. In addition, cells transformed by the two smallest fragments lacked the 19K species. All fragment-transformed cells contained small amounts of T antigens in the 32-52K size class, indicating that these proteins are encoded (or induced) by the smallest transforming fragment of 4.5%. Evidence is presented that the 19K protein is responsible for the induction of a number of transformed properties. © 1979.