Displacement Assay: Affinity evaluation of the tested compounds and their selectivity with respect to the different PARP isoforms of interest was assessed in a displacement assay.The identification of compounds capable of binding several PARP proteins is carried out through a screening method including the steps of a) providing a reaction mixture containing: the PARP protein isoform under investigation,a compound of formula (IP). b) comparing the polarization signal generated in the absence of the test compound with the one generated in the presence of different concentrations of the test compound, and c) evaluating the ability of the test compound to displace the compound of formula (IP) as defined above indicated from a decreased fluorescence polarization level. Preferably, for the screening method above cited, both the PARP protein and the 5H-phenanthridin-6-one-derived probe of formula (IP) are pre-mixed, or the PARP protein and the test compound are pre-mixed.
Enzyme Assay: In order to test the selectivity of substituents on piperazinotriazole ring within the PARP family, the selectivity of compound S3 and positive compound AZD2281 were tested.
PARP-2 and PARP-3 Enzymatic Assay: PARP-2 and PARP-3 enzymatic assays were conducted using commercial PARP-2/PARP-3 Chemiluminescent Assay Kit (BPS Biosciences) and the protocols with the kits. Briefly, histones were coated in a high binding plate first, and incubated with PARP-2 or PARP-3, and increasing concentrations of compounds for 0.5 h. Then, biotinylated NAD and activated DNA were added to the wells. The biotinylated PARylation product was measured by adding streptavidin-HRP and HRP substrates which produce chemiluminescence.
Biochemical Assay: The identification of compounds capable of binding several PARP proteins is carried out through a screening method including the steps of a) providing a reaction mixture containing: b) comparing the polarization signal generated in the absence of the test compound with the one generated in the presence of different concentrations of the test compound, and c) evaluating the ability of the test compound to displace the compound of formula (IP) as defined above indicated from a decreased fluorescence polarization level.The polarization signal can be measured, e.g., by a plate reader such as the Saphire2 (Tecan).