Dramatic changes in pre-60S subunit protein composition are caused by depletion of r-protein L19. (A–C) Preribosomes containing (gal) or lacking (glu) L19 were purified using TAP-tagged Nop7 as bait. (A) The protein composition of pre-60S subunits was analyzed by SDS-PAGE followed by silver staining and Western blotting. (B and C) Semiquantitative mass spectrometry (iTRAQ) was used to quantify the relative changes in levels of 60S subunit r-proteins (B) and AFs (C) in the presence and absence of L19. The ratios were normalized to levels of Nop7, and the fold change in log2 scale is shown for two biological replicates. Both samples of yeast grown in glucose were compared with a single sample grown in galactose. A complete dataset for AFs is shown in Fig. S2.