Figure 6.

The TFIID complex shows a reduced affinity for DCE mutants; a linear correlation exists between DCE mutant transcriptional activity and TFIID binding activity. Binding of DCE mutants (A) or the spacing mutants (B) to TFIID was assayed by agarose gel electrophoresis using rTFIIA and immunopurified HA-tagged HeLa TFIID. The arrow indicates the position of the rTFIIA/TFIID complex. Free probe runs at the bottom of the gel. Probes extend from −110 to +100 of the β-globin promoter and were PCR amplified by using a ³²P-labeled −110 primer to ensure that all probes had the same specific activity. Quantitation under each lane is relative to the wild-type βLONG TFIIA/TFIID complex and represents the mean of three to five experiments. (C) Regression analysis of the relationship between the transcriptional activity of the DCE mutants (+13/15, +22/24, +31/33, and +37/39 in Fig. 2), and the spacing mutants (Fig. 5), and their respective abilities to bind TFIID (Fig. 6 A and B).