DNA bends in TATA-binding protein center dot TATA complexes in solution are DNA sequence-dependent

The TATA-binding protein (TBP) initiates assembly of transcription preiniti ation complexes on eukaryotic class II promoters, binding to and restructur ing consensus and variant "TATA box" sequences. The sequence dependence of the DNA structure in TBP TATA complexes has been investigated in solution u sing fluorescence resonance energy transfer. The mean 5'dye-3'dye distance varies significantly among oligomers bearing the adenovirus major late prom oter sequence (AdMLP) and five single-site variants bound to Saccharomyces cerevisiae TBP, consistent with solution bend angles for AdMLP of 76 degree s and for the variants ranging from 30 degrees to 62 degrees, These solutio n bends contrast sharply with the corresponding co-crystal structures, whic h show similar to 80 degrees bends for all sequences. Transcription activit ies for these TATA sequences are strongly correlated with the solution bend angles but not with TBP.DNA binding affinities, Our results support a mode l in which transcription efficiency derives primarily from the sequence-dep endent structure of the TBP.TATA binary complex, Specifically, the distance distribution for the average solution structure of the TBP.TATA complex ma y reflect the sequence-dependent probability for the complex to assume a co nformation in which the TATA box DNA is severely bent. Upon assumption of t his geometry, the binary complex becomes a target for binding and correctly orienting the other components of the preinitiation complex.