Role of an adenovirus E2 promoter binding factor in E1A-mediated coordinate gene control

Abstract

A product of the adenovirus gene E1A is responsible for the stimulation of transcription from six viral promoters as well as at least two cellular promoters. We have detected a HeLa cell factor, termed E2 promoter binding factor (E2F), that appears to mediate the transcriptional stimulation of the viral E2 promoter. Competition experiments revealed that E2F did not recognize and bind to the E1B, E3, E4, or major late promoter sequences. Furthermore, three additional promoters stimulated by E1A, heat shock protein 70, beta-globin, and early simian virus 40, do not bind E2F. In contrast, the factor does recognize sequences in the E1A enhancer, and within the E1A enhancer are duplicated binding sites for E2F. Finally, a single E2F binding site from the E1A enhancer can confer increased transcription to a mouse beta-globin promoter, dependent on the action of the E1A gene product. This stimulation requires binding of E2F since methylation of the binding site, which blocks binding in vitro, reduces transcription stimulation in vivo. We, therefore, conclude that E2F is likely to be responsible for the E1A-mediated stimulation of the E1A gene as well as the E2 gene but is not involved in the activation of the other E1A-inducible promoters.