Diazaborine Treatment of Yeast Cells Inhibits Maturation of the 60S Ribosomal Subunit

• DOI: 10.1128/mcb.24.14.6476-6487.2004
• Publication Date: 2004-06-29T22:39:25Z
• Authors: Brigitte Pertschy; Gertrude Zisser; Hermine Schein; René Köffel; Gernot Rauch; Karlheinz Grillitsch; Christina Morgens...; Michael Durchschlag; Gregor Högenauer; Helmut Bergler
• Keywords: Boron Compounds; Cell Nucleus; 0301 basic medicine; Saccharomyces cerevisiae Proteins; Recombinant Fusion Proteins; Saccharomyces cerevisiae; Protein Subunits; 03 medical and health sciences; RNA, Ribosomal; Ribonucleoproteins, Small Nucleolar; RNA Precursors; Protein Processing, Post-Translational; Ribosomes

Diazaborine treatment of yeast cells was shown previously to cause accumulation of aberrant, 3'-elongated mRNAs. Here we demonstrate that the drug inhibits maturation of rRNAs for the large ribosomal subunit. Pulse-chase analyses showed that the processing of the 27S pre-rRNA to consecutive species was blocked in the drug-treated wild-type strain. The steady-state level of the 7S pre-rRNA was clearly reduced after short-term treatment with the inhibitor. At the same time an increase of the 35S pre-rRNA was observed. Longer incubation with the inhibitor resulted in a decrease of the 27S precursor. Primer extension assays showed that an early step in 27S pre-rRNA processing is inhibited, which results in an accumulation of the 27SA2 pre-rRNA and a strong decrease of the 27SA3, 27SB1L, and 27SB1S precursors. The rRNA processing pattern observed after diazaborine treatment resembles that reported after depletion of the RNA binding protein Nop4p/Nop77p. This protein is essential for correct pre-27S rRNA processing. Using a green fluorescent protein-Nop4 fusion, we found that diazaborine treatment causes, within minutes, a rapid redistribution of the protein from the nucleolus to the periphery of the nucleus, which provides a possible explanation for the effect of diazaborine on rRNA processing.