Pulse-chase analysis demonstrates abnormal pre-rRNA processing in TF-1 cells depleted of RPS19. Pulse-chase was carried out as described in “Materials and methods.” TF-1 cells infected with lentiviruses containing either siRNA B targeted to RPS19 (RPS19) or a scrambled siRNA (scrambled) were grown for 4 days in the presence (+) or absence (−) of DOX. Chase periods are shown above each lane.