title: The kinase activity of human Rio1 is required for final steps of cytoplasmic maturation of 40S subunits.
abstract: RIO proteins form a conserved family of atypical protein kinases. Humans possess three distinct RIO kinases-hRio1, hRio2, and hRio3, of which only hRio2 has been characterized with respect to its role in ribosomal biogenesis. Here we show that both hRio1 and hRio3, like hRio2, are associated with precursors of 40S ribosomal subunits in human cells. Furthermore, we demonstrate that depletion of hRio1 by RNA interference affects the last step of 18S rRNA maturation and causes defects in the recycling of several trans-acting factors (hEnp1, hRio2, hLtv1, hDim2/PNO1, and hNob1) from pre-40S subunits in the cytoplasm. Although the effects of hRio1 and hRio2 depletion are similar, we show that the two kinases are not fully interchangeable. Moreover, rescue experiments with a kinase-dead mutant of hRio1 revealed that the kinase activity of hRio1 is essential for the recycling of the endonuclease hNob1 and its binding partner hDim2 from cytoplasmic pre-40S. Kinase-dead hRio1 is trapped on pre-40S particles containing hDim2 and hNob1 but devoid of hEnp1, hLtv1, and hRio2. These data reveal a role of hRio1 in the final stages of cytoplasmic pre-40S maturation.
authors.affiliation: Institute of Biochemistry, ETH Zurich, Zurich, Switzerland.
authors.forename: Barbara
authors.initials: B
authors.lastname: Widmann
authors.forename: Franziska
authors.initials: F
authors.lastname: Wandrey
authors.forename: Lukas
authors.initials: L
authors.lastname: Badertscher
authors.forename: Emanuel
authors.initials: E
authors.lastname: Wyler
authors.forename: Jens
authors.initials: J
authors.lastname: Pfannstiel
authors.forename: Ivo
authors.initials: I
authors.lastname: Zemp
authors.forename: Ulrike
authors.initials: U
authors.lastname: Kutay
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D003593:Cytoplasm / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D034622:RNA Interference; D012323:RNA Processing, Post-Transcriptional; D012337:RNA, Ribosomal, 18S / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000378:metabolism; D054682:Ribosome Subunits, Small, Eukaryotic / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; C506664:NOB1 protein, human; D009687:Nuclear Proteins; D012337:RNA, Ribosomal, 18S; D016601:RNA-Binding Proteins; C506013:TXNL4B protein, human; D017346:Protein Serine-Threonine Kinases; C534426:RIO kinase 3, human; C469385:RIOK1 protein, human; C542171:RIOK2 protein, human
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