title: Proteomic analysis of the Arabidopsis nucleolus suggests novel nucleolar functions.
abstract: The eukaryotic nucleolus is involved in ribosome biogenesis and a wide range of other RNA metabolism and cellular functions. An important step in the functional analysis of the nucleolus is to determine the complement of proteins of this nuclear compartment. Here, we describe the first proteomic analysis of plant (Arabidopsis thaliana) nucleoli, in which we have identified 217 proteins. This allows a direct comparison of the proteomes of an important nuclear structure between two widely divergent species: human and Arabidopsis. The comparison identified many common proteins, plant-specific proteins, proteins of unknown function found in both proteomes, and proteins that were nucleolar in plants but nonnucleolar in human. Seventy-two proteins were expressed as GFP fusions and 87% showed nucleolar or nucleolar-associated localization. In a striking and unexpected finding, we have identified six components of the postsplicing exon-junction complex (EJC) involved in mRNA export and nonsense-mediated decay (NMD)/mRNA surveillance. This association was confirmed by GFP-fusion protein localization. These results raise the possibility that in plants, nucleoli may have additional functions in mRNA export or surveillance.
authors.affiliation: John Innes Centre, Norwich NR4 7UH, United Kingdom.
authors.forename: Alison F
authors.initials: AF
authors.lastname: Pendle
authors.forename: Gillian P
authors.initials: GP
authors.lastname: Clark
authors.forename: Reinier
authors.initials: R
authors.lastname: Boon
authors.forename: Dominika
authors.initials: D
authors.lastname: Lewandowska
authors.forename: Yun Wah
authors.initials: YW
authors.lastname: Lam
authors.forename: Jens
authors.initials: J
authors.lastname: Andersen
authors.forename: Matthias
authors.initials: M
authors.lastname: Mann
authors.forename: Angus I
authors.initials: AI
authors.lastname: Lamond
authors.forename: John W S
authors.initials: JW
authors.lastname: Brown
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Shaw
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000378:metabolism; D002466:Cell Nucleolus / Q000378:metabolism / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D005091:Exons; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D013058:Mass Spectrometry; D008856:Microscopy, Fluorescence; D040901:Proteomics; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017422:Sequence Analysis, DNA
chemical_list: D029681:Arabidopsis Proteins; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D012313:RNA