title: Assembly and maturation of the U3 snoRNP in the nucleoplasm in a large dynamic multiprotein complex.
abstract: The assembly and maturation of box C/D snoRNPs, factors essential for ribosome biogenesis, occur in the nucleoplasm. To investigate this process, we have analyzed non-snoRNP factors associated with the nucleoplasmic human U3 snoRNA. We show that both the precursor and mature length nucleoplasmic U3 snoRNAs are present in larger multiprotein complexes that contain the core box C/D proteins as well as many non-snoRNP factors linked to snoRNP assembly (TIP48, TIP49, Nopp140), RNA processing (TGS1, La, LSm4, hRrp46), and subcellular localization (CRM1, PHAX). Using RNAi, we show that most of these factors are essential for box C/D snoRNA accumulation. Furthermore, we demonstrate that the core proteins undergo a restructuring event that stabilizes their binding to the snoRNA. Importantly, restructuring, which may be mediated by the putative remodeling factor TIP49, appears to be linked to nucleolar localization. We believe that the assembly complex coordinates snoRNA processing, snoRNP assembly, restructuring, and localization.
authors.affiliation: Max-Planck-Institute of Biophysical Chemistry, Am Fassberg 11, D-37070 Göttingen, Germany. n.j.watkins@ncl.ac.uk
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Watkins
authors.forename: Ira
authors.initials: I
authors.lastname: Lemm
authors.forename: Dierk
authors.initials: D
authors.lastname: Ingelfinger
authors.forename: Claudia
authors.initials: C
authors.lastname: Schneider
authors.forename: Markus
authors.initials: M
authors.lastname: Hossbach
authors.forename: Henning
authors.initials: H
authors.lastname: Urlaub
authors.forename: Reinhard
authors.initials: R
authors.lastname: Lührmann
mesh_terms: D001483:Base Sequence; D015152:Blotting, Northern; D002460:Cell Line; D002466:Cell Nucleolus / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047468:Immunoprecipitation; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000502:physiology; D010750:Phosphoproteins / Q000502:physiology; D010802:Phylogeny; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000737:chemistry; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D020718:Ribonucleoproteins, Small Nucleolar / Q000737:chemistry / Q000502:physiology*; D012492:Salts / Q000737:chemistry; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection
chemical_list: C075564:NOLC1 protein, human; D009687:Nuclear Proteins; D010750:Phosphoproteins; D034741:RNA, Small Interfering; D020718:Ribonucleoproteins, Small Nucleolar; D012492:Salts; C117377:ribonucleoprotein, U3 small nucleolar; D012313:RNA