E1A transcription induction: enhanced binding of a factor to upstream promoter sequences

The adenovirus E1A gene product trans-activates a number of viral and cellular promoters. The mechanism for this transcriptional induction was investigated with an in vivo exoIII mapping technique to assay for proteins that interact with an E1A-inducible promoter. A protein bound to the early E2 promoter was detected in wild-type infected cells. In the absence of E1A induction, specific interactions at the promoter could not be detected, as indicated by the absence of an exoIII-protected fragment. However, if conditions were established that allowed transcription of the E2 gene in the absence of E1A, the same exoIII protection was observed as was found in the presence of E1A. These results suggest a model in which the efficient utilization of the E2 promoter is mediated by a cellular transcription factor. In the absence of E1A, the interaction can take place, but slowly and inefficiently in comparison with the interaction in the presence of E1A.