TATA-flanking Sequences Influence the Rate and Stability of TATA-binding Protein and TFIIB Binding

The kinetics of TATA-binding protein (TBP) and TFIIB binding were measured on a series of promoter constructs that had varying sequences within and flanking the TATA box. The flanking sequences were found to influence TBP stability even though they do not contact the protein. This occurs by altering the decay rate rather than the association rate. TFIIB association is accompanied by protein-protein cooperativity as indicated by the simultaneous release of both proteins in challenge experiments. The sequence of the TATA box and the sequences that flank it can influence the kinetics of the TFIIB.TBP.DNA complex. TFIIB can contribute to tighter TATA binding in two ways. It always slows the decay rate of TBP, but it can also increase the rate of association at promoters with certain combinations of TATA and flanking sequences. The results imply that the interplay between the TATA box and flanking elements leads to variations in the kinetics of preinitiation complex formation that may account for the observed effects of all of these diverse sequences on transcription.