Luciferase reporter assay

H1299 cells were transfected with DNA vectors encoding p53_WT or p53_PBM4 together with the Cignal p53 reporter mix (Qiagen). The Cignal p53 reporter mix contains a plasmid, encoding firefly luciferase, which is under the control of a minimal CMV promoter and tandem repeats of p53 transcriptional response elements. It also contains a plasmid, encoding renilla luciferase, which is constitutively expressed and used to normalize for transfection efficiencies and cell viability. 10 μM of the PARP inhibitor olaparib or DMSO as solvent control were added to the cells. After 24 h, cells were lyzed with the Dual-Glo luciferase reporter assay (Promega), according to the manufacturer's instructions. Firefly and renilla luciferase luminescence were analyzed in technical triplicates using a Varioscan Flash plate reader (Thermofisher Scientific). The transactivation activity was expressed as relative luminescence, which is the ratio of firefly luciferase luminescence to renilla luciferase luminescence.