title: Potential roles for ubiquitin and the proteasome during ribosome biogenesis.
abstract: We have investigated the possible involvement of the ubiquitin-proteasome system (UPS) in ribosome biogenesis. We find by immunofluorescence that ubiquitin is present within nucleoli and also demonstrate by immunoprecipitation that complexes associated with pre-rRNA processing factors are ubiquitinated. Using short proteasome inhibition treatments, we show by fluorescence microscopy that nucleolar morphology is disrupted for some but not all factors involved in ribosome biogenesis. Interference with proteasome degradation also induces the accumulation of 90S preribosomes, alters the dynamic properties of a number of processing factors, slows the release of mature rRNA from the nucleolus, and leads to the depletion of 18S and 28S rRNAs. Together, these results suggest that the UPS is probably involved at many steps during ribosome biogenesis, including the maturation of the 90S preribosome.
authors.affiliation: Laboratory of Receptor Biology and Gene Expression, Center for Cancer Research [corrected] National Cancer Institute, Bethesda, MD 20892, USA.
authors.forename: Diana A
authors.initials: DA
authors.lastname: Stavreva
authors.forename: Miyuki
authors.initials: M
authors.lastname: Kawasaki
authors.forename: Miroslav
authors.initials: M
authors.lastname: Dundr
authors.forename: Karel
authors.initials: K
authors.lastname: Koberna
authors.forename: Waltraud G
authors.initials: WG
authors.lastname: Müller
authors.forename: Teruko
authors.initials: T
authors.lastname: Tsujimura-Takahashi
authors.forename: Wataru
authors.initials: W
authors.lastname: Komatsu
authors.forename: Toshiya
authors.initials: T
authors.lastname: Hayano
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Isobe
authors.forename: Ivan
authors.initials: I
authors.lastname: Raska
authors.forename: Tom
authors.initials: T
authors.lastname: Misteli
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Takahashi
authors.forename: James G
authors.initials: JG
authors.lastname: McNally
mesh_terms: D002460:Cell Line; D002466:Cell Nucleolus / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors; D012322:RNA Precursors / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D012337:RNA, Ribosomal, 18S / Q000235:genetics / Q000378:metabolism; D012339:RNA, Ribosomal, 28S / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D025801:Ubiquitin / Q000032:analysis / Q000378:metabolism*
chemical_list: D009687:Nuclear Proteins; D061988:Proteasome Inhibitors; D012322:RNA Precursors; D012337:RNA, Ribosomal, 18S; D012339:RNA, Ribosomal, 28S; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex