The relationship between region E1a and E1b of human adenoviruses in cell transformation

Abstract

Baby rat kidney (BRK) cells were transfected either with intact region El DNA of adenovirus type 5 (Ad5) or with mixtures of DNA fragments containing the separated E1a and E1b regions. The results showed that mixtures of regions E1a and E1b transform with a similar efficiency as intact region E1. DNA fragments containing region E1b alone have no detectable transforming activity in primary BRK cells nor in established rat cell lines. When region Ela of Ad5 was combined with region E1b of Ad12 complete transformation was also obtained. Characterization of the cell lines transformed by separated E1a and E1b regions have led to the following conclusions: (1) Expression of region E1b is not dependent on specific linkage to region Ela as it occurs in the intact E1 region. (2) Region E1b is normally expressed into the corresponding major adenovirus T antigens (65000 and 19000 M r with region E1b of Ad5; 60000 and 19000 M r with E1b of Ad12). (3) Region E1b of Ad12 can be activated by region E1a of Ad5 indicating that the E1a regions of both serotypes are functionally similar in transformation. (4) Cell lines containing region E1b of Ad5 are weakly oncogenic in nude mice whereas cells containing E1b of Ad12 are highly oncogenic in nude mice, indicating that the degree of oncogenicity is determined by region E1b.