Effect of ∆NC mutation on FL RNA packaging into viruses. FL RNA was quantitated by RT-qPCR in NIH3T3 cells transfected with the MLV molecular clone: pRR88-WT or pRR88-∆NC (described in Grigorov et al. [2007]) or with an empty pSP72 vector (as control) and in the released viral particles. Mock controls were subtracted from assays, and the measured RNA copy numbers were scaled to the total number of cells present in the dish and to the whole-cell supernatant. The graph shows the mean ± SD, n = 2 independent transfections.