Efficiency of plasmid transfection of PTE cells with active or inactive endonucleases. (A) Expression of CFP after pECFP-N1 plasmid transfection in DNase I KO PTE cells is higher than in WT cells. KO versus WT (21 ± 5% vs. 8 ± 5% transfected cells, n = 3, *p < 0.013; 32 ± 6% vs. 18 ± 5% transfected cells, n = 3, **p < 0.025). Two time-points have been used, 24 h and 48 h incubation after transfection. The second time-point shows higher transfection efficiency and has been chosen for experiment B, where EndoG WT and KO cells have been transfected with the same plasmid. (B) Expression of CFP 48 h after pECFP plasmid transfection in EndoG KO PTE cells is higher than in WT cells (19 ± 5% vs. 8 ± 5% CFP-positive cells, n = 6, *p < 0.001). CFP, cyan fluorescent protein.