Infection profiles of GFP-expressing lentiviruses versus MLV were initially assessed on wild-type (WT) HEK293T cells as well as isogenic derivatives that were knocked out for LEDGF/p75 (LKO for LEDGF knockout), CPSF6 (CKO), or both factors (DKO for double knockout) (17, 41) (Fig. 1A). Here, CPSF6 is linked to infection.