A series of deletion mutants spanning the adenovirus early region IV (EIV) promoter were tested for transcription activity in vitro. At least three elements were found to be important for maximal transcription in HeLa whole-cell extracts. Deletion of the TATA box drastically reduced the transcription activity from the EIV promoter. Sequences between nucleotides -58 and -44 are also important for efficient transcription since deletion of this region reduced activity by 50%. More importantly, sequences residing upstream from -140 critically influence the level of EIV transcription. Deletion of sequences between nucleotides -325 (the right terminus of adenovirus genome) and -140 reduced the level of transcription more than 10-fold. It is possible that a specific cellular factor stimulates EIV transcription by recognition of these upstream sequences. The dependence of transcription from the EIV promoter on a distal upstream element may explain some aspects of the regulation of this promoter.
