1. Fig. 5 Metarrestin treatment induces nucleolar structure changes.
Metarrestin treatment induces nucleolar structure changes. (A) Nucleoli lose their typical three substructures, as seen in untreated or DMSO-treated cells (arrows indicate DFC, FC, and GC), and develop nucleolar capping (enlarged inserts) upon treatment with metarrestin in HeLa cells and tumor tissues. Representative electron micrographs are shown for HeLa cells (treated at 1 μM for 24 hours), primary pancreatic tumors, and liver metastases from NSG PANC1 mice treated with vehicle (top) or metarrestin (10 mg/kg) (bottom) for 7 days. Mice were harvested 1 hour after last metarrestin dose (inset shows nucleoli). Scale bars, 1 μm. (B) Quantitative evaluation of the EM images demonstrated that average nucleolar area was reduced in metarrestin-treated cell lines and tissues compared to vehicle control (****P < ). One hundred nucleoli were randomly selected and analyzed to calculate nucleolar area as {[(largest + shortest diameter)/2]2 × π}. The comparison of mean nucleolar areas was performed using two-tailed Mann-Whitney U test, n = 4 animals per group. (C) The changes in nucleolar architecture induced by metarrestin treatment were reflected in the redistribution of Pol I transcription factor, UBF, into cap-like structures (capping) (white arrows), corresponding to the loss of PNCs (green panel, orange arrows). As shown in the merge panel, the capping of UBF reflects the segregation of the fibrillar components from the granular components, as seen in EM images in (A). (D) Metarrestin interferes with ribosomal biogenesis. An inducible GFP-RPL29–expressing cell line synthesizes GFP-RPL29 when treated with tetracyclin (second panels). When cells were treated with 1 μM metarrestin before tetracycline induction, the newly synthesized proteins accumulated in the nucleoli and nuclei (fourth panels) compared to the DMSO control–treated cells (third panels). (C and D) Scale bars, 5 μm.
Kevin J. Frankowski et al., Sci Transl Med 2018;10:eaap8307
Published by AAAS