Transactivation of Host and Viral Genes by the Adenovirus E1B 19K Tumor Antigen

Adenovirus contains two nuclear oncogenes, the EIA and EIB genes, which cooperatively can transform cells through mechanisms that are not understood. The transcriptional activities of the E1A gene (transactivation and repression) are well studied. Using transient expression assays, we show here that the 19,000-Da E1B gene product can also activate all the adenovirus early promoters (E1A, E1B, E2e, E3 and E4) and a cellular heat shock gene promoter (hsp70), but not the adenovirus late promoters (IX, IVa2, MLP and E2L). The effect is greatest under conditions where cell growth is inhibited, and appears to operate at the transcriptional level. Possible interactions with enhancer elements are discussed. Although the E1B stimulatory effect does not require the presence of E1A gene products, a synergistic effect is obtained in the presence of E1A 13S product. This activity of the E1B gene is also observed during virus infection and is likely to have important consequences in lytically infected and transformed cells.