Topological localization of the human transcription factors IIA, IIB, TATA box-binding protein, and RNA polymerase II-associated protein 30 on a class II promoter.

The human general transcription factors IIA and IIB bind directly to the TATA box-binding protein (TBP), and modulate transcription initiation by RNA polymerase II. RAP30, the small subunit of TFIIF, binds to TFIIB and RNA polymerase II and recruits RNA polymerase II to a preinitiation complex containing TBP and TFIIB. By using the adenovirus 2 major late promoter tagged site-specifically with the photoactivatible cross-linking reagent N3R-dUMP we have localized TBP, two subunits of TFIIA (A35 and A21), TFIIB, and RAP30 along promoter DNA. TFIIA cross-linked to the coding strand opposite TBP at the TATA box and cross-linked upstream of TBP around position -40. RAP30 cross-linked strongly and TFIIB weakly to the coding strand just downstream of TBP at -19. We interpret these data in the context of a molecular structure for the TBP promoter complex.