Northern blot analysis demonstrates abnormal pre-rRNA processing in TF-1 cells depleted of RPS19. Total RNA was isolated from TF-1 cells, fractionated on 1.5% formaldehyde-agarose gels, transferred to zetaprobe, and hybridized with oligonucleotides complementary to different regions of the rRNA primary transcript. The siRNAs present in each cell line are listed above each lane. Cell lines in lanes labeled A and B express 2 different siRNAs targeting RPS19. Sc indicates scrambled siRNA. Cell lines were grown for 4 days in the presence (+DOX) or absence (−DOX) of 0.5 μg/mL DOX. Panels are designated according to the oligonucleotide used for hybridization. Pre-rRNAs hybridizing with the different oligonucleotide probes are designated with arrows to the right or left of the panels. Illustrations of rRNA species hybridizing with different probes are included to the sides of each image. Filled boxes represent mature rRNAs: 18S, ▪; 5.8S, ⊡; 28S, ▨.