title: atBRX1-1 and atBRX1-2 are involved in an alternative rRNA processing pathway in Arabidopsis thaliana.
abstract: Ribosome biogenesis is an essential process in all organisms. In eukaryotes, multiple ribosome biogenesis factors (RBFs) act in the processing of ribosomal (r)RNAs, assembly of ribosomal subunits and their export to the cytoplasm. We characterized two genes in Arabidopsis thaliana coding for orthologs of yeast BRX1, a protein involved in maturation of the large ribosomal subunit. Both atBRX1 proteins, encoded by AT3G15460 and AT1G52930, respectively, are mainly localized in the nucleolus and are ubiquitously expressed throughout plant development and in various tissues. Mutant plant lines for both factors show a delay in development and pointed leaves can be observed in the brx1-2 mutant, implying a link between ribosome biogenesis and plant development. In addition, the pre-rRNA processing is affected in both mutants. Analysis of the pre-rRNA intermediates revealed that early processing steps can occur either in the 5' external transcribed spacer (ETS) or internal transcribed spacer 1 (ITS1). Interestingly, we also find that in xrn2 mutants, early processing events can be bypassed and removal of the 5' ETS is initiated by cleavage at the P' processing site. While the pathways of pre-rRNA processing are comparable to those of yeast and mammalian cells, the balance between the two processing pathways is different in plants. Furthermore, plant-specific steps such as an additional processing site in the 5' ETS, likely post-transcriptional processing of the early cleavage sites and accumulation of a 5' extended 5.8S rRNA not observed in other eukaryotes can be detected.
authors.affiliation: Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt/Main, Germany.
authors.forename: Benjamin L
authors.initials: BL
authors.lastname: Weis
authors.affiliation: Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt/Main, Germany.
authors.forename: Denise
authors.initials: D
authors.lastname: Palm
authors.affiliation: Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt/Main, Germany.
authors.forename: Sandra
authors.initials: S
authors.lastname: Missbach
authors.affiliation: Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt/Main, Germany Institute for Molecular Biology, Georg-August University, 37073 Göttingen, Germany.
authors.forename: Markus T
authors.initials: MT
authors.lastname: Bohnsack
authors.affiliation: Department of Biosciences, Molecular Cell Biology of Plants, Goethe University, 60438 Frankfurt/Main, Germany Cluster of Excellence Frankfurt, Goethe University, 60438 Frankfurt/Main, Germany Center of Membrane Proteomics, Goethe University, 60438 Frankfurt/Main, Germany schleiff@bio.uni-frankfurt.de.
authors.forename: Enrico
authors.initials: E
authors.lastname: Schleiff
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics*; D002466:Cell Nucleolus / Q000235:genetics / Q000378:metabolism; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D050505:Mutant Proteins / Q000235:genetics; D063245:Plant Development / Q000235:genetics; D018515:Plant Leaves / Q000235:genetics / Q000254:growth & development; D012322:RNA Precursors / Q000235:genetics; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics*; D012335:RNA, Ribosomal / Q000235:genetics*; D016601:RNA-Binding Proteins / Q000235:genetics*; D054683:Ribosome Subunits, Large, Eukaryotic / Q000235:genetics* / Q000378:metabolism
chemical_list: C000596819:AT1G52930 protein, Arabidopsis; C000596818:AT3G15460 protein, Arabidopsis; D029681:Arabidopsis Proteins; D021903:DNA, Ribosomal Spacer; D050505:Mutant Proteins; D012322:RNA Precursors; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins
keywords: 60S subunit maturation; Arabidopsis thaliana; Brx1; Xrn2; rRNA processing; ribosome biogenesis