title: Human H/ACA small nucleolar RNPs and telomerase share evolutionarily conserved proteins NHP2 and NOP10.
abstract: The H/ACA small nucleolar RNAs (snoRNAs) are involved in pseudouridylation of pre-rRNAs. In the yeast Saccharomyces cerevisiae, four common proteins are associated with H/ACA snoRNAs: Gar1p, Cbf5p, Nhp2p, and Nop10p. In vitro reconstitution studies showed that four proteins also specifically interact with H/ACA snoRNAs in mammalian cell extracts. Two mammalian proteins, NAP57/dyskerin (the ortholog of Cbf5p) and hGAR1, have been characterized. In this work we describe properties of hNOP10 and hNHP2, human orthologs of yeast Nop10p and Nhp2p, respectively, and further characterize hGAR1. hNOP10 and hNHP2 complement yeast cells depleted of Nhp2p and Nop10p, respectively. Immunoprecipitation experiments with extracts from transfected HeLa cells indicated that epitope-tagged hNOP10 and hNHP2 specifically associate with hGAR1 and H/ACA RNAs; they also interact with the RNA subunit of telomerase, which contains an H/ACA-like domain in its 3' moiety. Immunofluorescence microscopy experiments showed that hGAR1, hNOP10, and hNHP2 are localized in the dense fibrillar component of the nucleolus and in Cajal (coiled) bodies. Deletion analysis of hGAR1 indicated that its evolutionarily conserved core domain contains all the signals required for localization, but progressive deletions from either the N or the C terminus of the core domain abolish localization in the nucleolus and/or the Cajal bodies.
authors.affiliation: Friedrich-Miescher Institut, CH-4058 Basel, Switzerland.
authors.forename: V
authors.initials: V
authors.lastname: Pogacić
authors.forename: F
authors.initials: F
authors.lastname: Dragon
authors.forename: W
authors.initials: W
authors.lastname: Filipowicz
mesh_terms: D000595:Amino Acid Sequence; D018797:Cell Cycle Proteins / Q000378:metabolism; D002466:Cell Nucleolus / Q000737:chemistry; D017353:Gene Deletion; D005816:Genetic Complementation Test; D006367:HeLa Cells; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D020537:RNA, Small Nucleolar / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D017411:Ribonucleoproteins, Small Nuclear; D020718:Ribonucleoproteins, Small Nucleolar / Q000737:chemistry* / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D019098:Telomerase / Q000737:chemistry*
chemical_list: D018797:Cell Cycle Proteins; C112148:DKC1 protein, human; C485802:GAR1 protein, human; C407731:GAR1 protein, mammalian; C416929:NHP2 protein, human; C416930:NOP10 protein, human; D009687:Nuclear Proteins; D020537:RNA, Small Nucleolar; D016601:RNA-Binding Proteins; D017411:Ribonucleoproteins, Small Nuclear; D020718:Ribonucleoproteins, Small Nucleolar; D019098:Telomerase