Fig. 6: Effect of inhibitor binding on PARP1 structure and DNA binding properties.

a Secondary structure analysis of PARP1 upon binding to veliparib. Difference spectra of amide I bands of PARP1 bound to DNA_blunt were calculated before and after the addition of 10 µM veliparib. Average curves and SDs (grey) of two experiments are plotted. b Secondary structure analysis of PARP1 upon binding to olaparib. Difference spectra of amide I bands of PARP1 bound to DNA_blunt before and after the addition of 10 µM veliparib were calculated. Average curves and SDs (grey) of two experiments are plotted. c Evaluation of inhibitory effect of veliparib and olaparib. Dissociation of PARP1 from DNA_blunt upon addition of 100 µM NAD⁺ in the presence of inhibitor was tested. Time-dependent intensity decrease of the amide II band (1548 cm⁻¹) was analysed. Intensity of the amide II band before addition of NAD⁺ was set to 100%. d Analysis of ‘trapping’ effect of olaparib. Binding of PARP1 to immobilised DNA_blunt was competed by the addition of free DNA_blunt in the supernatant in the absence or in the presence of olaparib. Time-dependent intensity decrease of the amide I band (1645 cm⁻¹) was analysed. Intensity of the amide I band before addition of free DNA_blunt was set to 100%. Source data are provided as a Source Data file.