Investigating the allosteric reverse signalling of PARP inhibitors with microsecond molecular dynamic simulations and fluorescence anisotropy

PARP1, a multidomain enzyme that recognizes DNA damages, plays a crucial role for DNA repair and genome integrity.1 Its inhibition has been investigated as therapeutic opportunity for different pathologies including cancers, diabetes, stroke and cardiac failure.2 Two different inhibitors of PARP1 sharing a similar binding mode and same affinities for the enzyme have different efficacies. It has been experimentally shown that Olaparib traps PARP1 on DNA damaged sites, causing a socalled “poisoning effect”, whereas Veliparib is devoid of such activity.3 In this study we have used microsecond molecular dynamics to study the allosteric reverse signalling that is at the basis of such an effect. We show that Olaparib, but not Veliparib and HYDAMTIQ, is able to induce a specific conformational drift of the WGR domain of PARP-1, which stabilizes PARP-1/DNA complex through the locking of several salt bridge interactions. Fluorescence anisotropy assays support such a mechanism, providing the first experimental evidence that HYDAMTIQ, a potent PARP inhibitor with neuroprotective properties, is less potent than Olaparib to trap PARP-1/DNA complex.