title: Nop9 binds the central pseudoknot region of 18S rRNA.
abstract: The assembly of eukaryotic ribosomes requires numerous factors that transiently associate with evolving pre-ribosomal particles. The Pumilio repeat-containing protein Nop9 briefly associates with the 90S pre-ribosome during its co-transcriptional assembly. Here, we show that Nop9 specifically binds an 11-nucleotide sequence of 18S rRNA that forms the 3΄ side of the central pseudoknot and helix 28 in the mature subunit. Crystal structures of Nop9 in the free and RNA-bound states reveal a new type of Pumilio repeat protein with a distinct structure, target sequence and RNA-binding mode. Nop9 contains 10 Pumilio repeats arranged into a U-shaped scaffold. The target RNA is recognized by two stretches of repeats in a bipartite manner, and three central bases are unrecognized as a result of the degeneracy of repeats 6 and 7. Our data suggest that Nop9 regulates the folding of 18S rRNA at early assembly stages of 90S.
authors.affiliation: Department of Biochemistry and Molecular Biology, College of Life Sciences, Beijing Normal University, Beijing 100875, China.|National Institute of Biological Sciences, Beijing 102206, China.|Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Bing
authors.initials: B
authors.lastname: Wang
authors.affiliation: Key Laboratory of RNA Biology, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
authors.forename: Keqiong
authors.initials: K
authors.lastname: Ye
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D008958:Models, Molecular; D011485:Protein Binding; D012337:RNA, Ribosomal, 18S / Q000737:chemistry* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000378:metabolism
chemical_list: C525831:Nop9 protein, S cerevisiae; D012337:RNA, Ribosomal, 18S; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins