Transcription factor IIA of wheat and human interacts similarly with the adenovirus-2 major late promoter

Transcription factor IIA (TFIIA) is a necessary component of many RNA polymerase II transcription complexes. Assembly of the transcription complex begins when TFIIA interacts with the promoter. We have previously purified wheat germ TFIIA to homogeneity and demonstrated that it substitutes for human TFIIA in a human in, vitro transcription system which utilizes the adenovirus-2 major late promoter (Ad-2 MLP). We now show, by gel retardation assays, that wheat TFIIA interacts with the Ad-2 MLP. Extensively purified human (HeLa) TFIIA interacts with the Ad-2 MLP similarly. Both wheat and human TFIIA interact with a DNA fragment comprising the minimal promoter region ( -51 +32) but not with upstream or downstream regions. With both TFIIAs multiple complexes form; the fastest wheat TFIIA DNA complex appears to be larger than the corresponding human TFIIA DNA complex. Limited point mutation analysis of the Ad-2 MLP demonstrates that changes at -30 (TATAA region), +1, and -1 diminish TFIIA binding, but a change at -40 does not. DNA footprint analysis of this region is not definitive, but does indicate that following TFIIA binding there are changes in the pattern of hypersensitive sites.