CYCLOSPORINE-A INHIBITS THE ACTIVITY OF A TATA BOX-BINDING PROTEIN THAT IS REQUIRED FOR TRANSCRIPTION FROM THE ADENOVIRUS MAJOR LATE PROMOTER

Nuclear extracts from P1798 lymphoma cells support transcription from the adenovirus major late promotor (AdMLP) and the human histone H4 promoter. Nuclear extracts prepared from P1798 cells treated with 1 mug/ml cyclosporine A for 24 h fail to support transcription from AdMLP, whereas transcription from the histone H4 promoter is unimpaired. Both control and cyclosporine-treated extracts contain proteins that interact with synthetic deoxyoligonucleotides that correspond to the CAAT box, TATA box, and upstream stimulatory element of AdMLP. Cyclosporine had no discernible qualitative or quantitative effect upon such DNA-protein interactions, as observed by gel mobility shift assays. Analysis of 5' deletion mutants of AdMLP indicates that deletion of sequences upstream of the TATA box reduces AdMLP transcription by only 50%. This observation suggests that cyclosporine A, which inhibits AdMLP transcription by >90%, is unlikely to act through changes in the amount or activity of upstream activators such as upstream stimulatory factor- or CAAT box-binding proteins. On the other hand, deletion of TATA box sequences between -50 and -11 base pairs virtually eliminates transcription from AdMLP in vitro. A partially purified TFIID fraction was obtained from control P1798 nuclear extracts. The TFIID fraction reconstitutes transcription from AdMLP when added to extracts from cyclosporine A-treated cells. Recombinant TATA box-binding protein also reconstitutes transcription from AdMLP in cyclosporine A-treated extracts. These results are consistent with the hypothesis that cyclosporine A regulates the activity of a subset of general transcription factors which are required for initiation from some promoters (such as AdMLP) but not from others (such as histone H4).