An RNA polymerase II transcription factor binds to an upstream element in the adenovirus major late promoter.

A gel electrophoresis DNA binding assay has been used to identify proteins in HeLa cell extracts that specifically bind to the major late promoter of adenovirus. A major late promoter transcription factor MLTF has been detected as a discrete protein-DNA complex. MLTF binds specifically and with high affinity to sequences upstream of the TATA box of the major late promoter. This factor protects a 17 bp (-50 to -66) region in a DNAase I footprinting assay. The same region has been shown to be important for efficient transcription from the major late promoter both in vivo and in vitro. MLTF stimulates in vitro transcription only from a template containing this upstream region. The binding, footprinting, and transcription-stimulatory activities of MLTF cofractionate through two chromatographic steps. These results suggest that direct binding of MLTF to an upstream element activates transcription from the major late promoter.