title: Nucleolar KKE/D repeat proteins Nop56p and Nop58p interact with Nop1p and are required for ribosome biogenesis.
abstract: Different point mutations in the nucleolar protein fibrillarin (Nop1p in Saccharomyces cerevisiae) can inhibit different steps in ribosome synthesis. A screen for mutations that are synthetically lethal (sl) with the nop1-5 allele, which inhibits pre-rRNA processing, identified NOP56. An independent sl mutation screen with nop1-3, which inhibits pre-rRNA methylation, identified a mutation in NOP58. Strikingly, Nop56p and Nop58p are highly homologous (45% identity). Both proteins were found to be essential and localized to the nucleolus. A temperature-sensitive lethal mutant allele, nop56-2, inhibited many steps in pre-rRNA processing, particularly on the pathway of 25S/5.8S rRNA synthesis, and led to defects in 60S subunit assembly. Epitope-tagged constructs show that both Nop56p and Nop58p are associated with Noplp in complexes, Nop56p and Nop1p exhibiting a stoichiometric association. These physical interactions presumably underlie the observed sl phenotypes. Well-conserved homologs are present in a range of organisms, including humans (52% identity between human hNop56p and yeast Nop56p), suggesting that these complexes have been conserved in evolution.
authors.affiliation: Laboratoire DyOGen, Institut Albert Bonniot, Université Grenoble I, La Tronche, France.
authors.forename: T
authors.initials: T
authors.lastname: Gautier
authors.forename: T
authors.initials: T
authors.lastname: Bergès
authors.forename: D
authors.initials: D
authors.lastname: Tollervey
authors.forename: E
authors.initials: E
authors.lastname: Hurt
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D017124:Conserved Sequence; D004271:DNA, Fungal / Q000235:genetics; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D006801:Humans; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D017354:Point Mutation; D020718:Ribonucleoproteins, Small Nucleolar; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D017386:Sequence Homology, Amino Acid
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins; C064793:NOP1 protein, S cerevisiae; D009687:Nuclear Proteins; D020718:Ribonucleoproteins, Small Nucleolar; D029701:Saccharomyces cerevisiae Proteins