Fig. 4: Kinetic analysis of the influence of force on TBP-induced DNA bending.

a Relative ratios of low FRET (unbound DNA, grey) to high FRET state (TBP/DNA complex, yellow) in a kinetic experiment performed on diffusing molecules showing the relative fraction of the TBP/DNA complex to the unbent U6 promoter at 0 and 6.0 pN. Dwell times were calculated by deconvolution with a perturbation-relaxation model. Data were fitted with a mono-exponential function. b Representative FRET efficiency–time plot of a single confocal time-course experiment at 0 pN force. TBP (20 nM) was added at 2 min (red arrow). Areas used for calculating the ratio of low and high FRET are indicated by blue boxes. c Dwell-time histograms of the U6 promoter in the unbent (grey) and bent (yellow) state at 0 and 6.6 pN force. d Representative donor (green) and acceptor (red) intensity–time trace from single-molecule TIRF microscopy experiments and the resulting FRET efficiency (blue) fitted with the idealised two-state trace (black) of TBP binding to the U6 promoter at 0 pN force. The low FRET and high FRET states are highlighted in grey and yellow, respectively. e Comparison of dwell times in the bent and unbent state for TBP-containing initiation complexes at 0 and 6.0 pN (AdMLP) or 6.6 pN (U6). Mean ± s.e.m. derived via error propagation from the exponential fit (see Supplementary Table 3 for the number of analysed molecules). Connecting lines between data points are meant as visual guides and do not represent interpolations (Supplementary Figs. 8 and 9 and Supplementary Table 3).