4-thiouridine inhibits rRNA synthesis and causes a nucleolar stress response

• DOI: 10.4161/rna.26214
• Publication Date: 2013-09-11T16:02:23Z
• Authors: Kaspar Burger; Bastian Mühl; Markus Kellner; Michaela Rohrmoser; Anita Gruber-Eber; Lukas Windhager; Caroline C Friedel; Lars Dölken; Dirk Eick
• Keywords: 0301 basic medicine; Staining and Labeling; Cell Cycle; Thiouridine; 4-thiouridine; Ribosomal RNA; rRNA processing; p53; Nucleolar stress; RNA labeling; Nucleophosmin; Mice; 03 medical and health sciences; RNA, Ribosomal; Stress, Physiological; Animals; RNA Processing, Post-Transcriptional; Nucleophosmin; Ribosomes; Cell Nucleolus

High concentrations (> 100 µM) of the ribonucleoside analog 4-thiouridine (4sU) is widely used in methods for RNA analysis like photoactivatable-ribonucleoside-enhanced crosslinking and immunoprecipitation (PAR-CLIP) and nascent messenger (m)RNA labeling (4sU-tagging). Here, we show that 4sU-tagging at low concentrations ≤ 10 µM can be used to measure production and processing of ribosomal (r)RNA. However, elevated concentrations of 4sU (> 50 µM), which are usually used for mRNA labeling experiments, inhibit production and processing of 47S rRNA. The inhibition of rRNA synthesis is accompanied by nucleoplasmic translocation of nucleolar nucleophosmin (NPM1), induction of the tumor suppressor p53, and inhibition of proliferation. We conclude that metabolic labeling of RNA by 4sU triggers a nucleolar stress response, which might influence the interpretation of results. Therefore, functional ribosome biogenesis, nucleolar integrity, and cell cycle should be addressed in 4sU labeling experiments.