Luciferase activity upon retroviral transfer of mRNA into 293FT cells. 293FT cells were transduced with 100 μl supernatants containing retroviral particles harvested 48 h post-transfection. 3 or 6 h post-transduction, cells were lysed and luciferase activity was measured. We observed a statistically significant difference between the control condition 4 and all the test constructs (5 to 10) (p-value < 0,03). Statistical comparisons between the different constructs were performed on the 3 hours time-point and evaluated using a Wilcoxon-Mann–Whitney analysis. hptr, hours post-transfection. NT: untransfected cells. Number of experiments, N = 3.