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A series of deletion mutants spanning the promoter of the adenovirus early-region IV (EIV) gene were tested for transcriptional activity, using both in vitro and in vivo assays. Four distinct domains had additive effects on efficient transcription from the EIV promoter in HeLa whole-cell extracts. The first resided 20 to 27 bases upstream of the initiation site and included the TATA box. Deletion of the TATA box drastically reduced the transcriptional activity in vitro but had a lesser effect in vivo. The second region extended from -32 to -177 and contained two 17-base-pair inverted repeats, centered around -40 and -162. Sequences lying between -140 and -173 were important for efficient transcription since deletion of this region reduced the activity fourfold. Deletion of either one of the two inverted repeats or insertion of DNA fragments between them resulted in the synthesis of extra transcripts that initiated at sites upstream from the EIV site. The third region was located between -198 and -250 and contains three guanosine-plus-cytosine-rich sequences, present around -212 (GGGCGG), -233 (GGGCGG), and -251 (CGCGGG). The fourth, most upstream region was located between -260 and -307. Deletion of this region, which contains the NF-1 factor-binding site, slightly reduced transcriptional activity both in vivo and in vitro. The data indicate that multiple cis-acting elements are required for efficient transcription from the EIV promoter in both in vitro and in vivo systems.

We constructed a series of mutations that delete sequences in the promoter region of the early-region IV (EIV) promoter of adenovirus type 5. We fused these promoter mutations to the coding sequences of either the chloramphenicol acetyltransferase or the dihydrofolate reductase (DHFR) gene and tested the ability of a cotransfected EIa gene to stimulate EIV expression. All of the mutations tested were stimulated in these assays, implying that no specific sequence is required for stimulation. Two mutant promoters, deleted for either the TATA box or the region residing between -39 and -177 upstream from the cap site of EIV mRNA, did show a reduced level of stimulation by the EIa products. To assess the effects of the EIA gene products on expression from an EIV promoter integrated into the chromosome, we isolated CHO cell lines containing EIV-DHFR chimeric genes. After introduction of the EIa gene with a second selectable marker, expression from all mutant EIV-DHFR genes was increased. Surprisingly, one mutant promoter, deleted for sequences between -39 and -177, lost the ability to respond to the EIa region on passage of cells, although deletions in any part of the region still retained this ability. These results demonstrate that multiple elements residing between -39 and -177 in the EIV promoter are necessary to maintain susceptibility of the integrated promoter to regulation.