title: Diazaborine treatment of yeast cells inhibits maturation of the 60S ribosomal subunit.
abstract: 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.
authors.affiliation: Institut für Molekularbiologie, Biochemie und Mikrobiologie, Karl-Franzens-Universität Graz, Austria.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Pertschy
authors.forename: Gertrude
authors.initials: G
authors.lastname: Zisser
authors.forename: Hermine
authors.initials: H
authors.lastname: Schein
authors.forename: René
authors.initials: R
authors.lastname: Köffel
authors.forename: Gernot
authors.initials: G
authors.lastname: Rauch
authors.forename: Karlheinz
authors.initials: K
authors.lastname: Grillitsch
authors.forename: Christina
authors.initials: C
authors.lastname: Morgenstern
authors.forename: Michael
authors.initials: M
authors.lastname: Durchschlag
authors.forename: Gregor
authors.initials: G
authors.lastname: Högenauer
authors.forename: Helmut
authors.initials: H
authors.lastname: Bergler
mesh_terms: D001896:Boron Compounds / Q000494:pharmacology*; D002467:Cell Nucleus / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D012322:RNA Precursors / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020718:Ribonucleoproteins, Small Nucleolar / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D001896:Boron Compounds; C088476:NOP4 protein, S cerevisiae; D021122:Protein Subunits; D012322:RNA Precursors; D012335:RNA, Ribosomal; D011993:Recombinant Fusion Proteins; D020718:Ribonucleoproteins, Small Nucleolar; D029701:Saccharomyces cerevisiae Proteins; C032255:1,2-dihydro-1-hydroxy-6-methyl-2-(propanesulfonyl)-thieno(3,2D)(1,2,3)-diazaborine