In order to assess whether the EGFP expressed in cells infected with a mutant virus originated from integrase-independent integrated provirus or from non-integrated episomal viral DNA, Rad18+/+ and Rad18−/− cells were inoculated with a HIV-1 retroviral vector–derived virus harboring a catalytically inactive integrase and split 1:10 at day 2, 5, and 9 post-infection. This evidence concerns the gene RAD18 and infection.