Transcription from the adenovirus major late promoter uses redundant activating elements

The adenovirus major late promoter (MLP) has been analyzed by constructing recombinant viral genomes containing mutations in possible promoter elements. Single base pair changes in the TATA box had no effect on viral replication, and MLP expression, as measured by the accumulation of late mRNAs, was at wild type levels. However, a double mutation in the TATA box reduced viral replication and MLP expression, demonstrating that the TATA box is important, although not essential, for maximal activity in virus. Primer extension analysis showed that the mRNAs were initiated at the correct position. A mutation in the CAAT box was viable, and had only minor effects on MLP expression. However, this mutation when coupled to a single mutation in the TATA box, severely reduced viral replication and expression from the MLP. Similarly, a viable mutation in the UPE, shown previously to abolish binding of USF, coupled to a single mutation in the TATA box was lethal. These results suggest that both USF and the CAAT box binding factor CP1 can interact with TFIID to effect activation, and thus that the mechanism of activation is functionally redundant.