PIM inhibition results in pre-rRNA processing defects. (A) Schematic showing pre-rRNA isoforms and positions of internal transcribed spacer (ITS) 1 (orange vertical bar) and 2 (yellow vertical bar) probes. Mature rRNA sequences within precursors are depicted as blue rectangular boxes, and spacers are depicted as black lines. Adapted from Tafforeau et al²⁹ with permission. (B) Northern blot analysis for AZD1208-treated MOLM-16 and EOL-1 cells using ITS1 (left) and ITS2 (right) probes. Autoradiograms showing ITS1 probe hybridization are presented at 2 different exposures (top and bottom panels) to permit optimal visualization of all rRNA intermediates. ∗aberrant 18S-E intermediate. The 18S rRNA abundance was analyzed by methylene blue staining of northern blot membranes.