title: The N-terminal extension of yeast ribosomal protein L8 is involved in two major remodeling events during late nuclear stages of 60S ribosomal subunit assembly.
abstract: Assaying effects on pre-rRNA processing and ribosome assembly upon depleting individual ribosomal proteins (r-proteins) provided an initial paradigm for assembly of eukaryotic ribosomes in vivo-that each structural domain of ribosomal subunits assembles in a hierarchical fashion. However, two features suggest that a more complex pathway may exist: (i) Some r-proteins contain extensions that reach long distances across ribosomes to interact with multiple rRNA domains as well as with other r-proteins. (ii) Individual r-proteins may assemble in a stepwise fashion. For example, the globular domain of an r-protein might assemble separately from its extensions. Thus, these extensions might play roles in assembly that could not be revealed by depleting the entire protein. Here, we show that deleting or mutating extensions of r-proteins L7 (uL30) and L35 (uL29) from yeast reveal important roles in early and middle steps during 60S ribosomal subunit biogenesis. Detailed analysis of the N-terminal terminal extension of L8 (eL8) showed that it is necessary for late nuclear stages of 60S subunit assembly involving two major remodeling events: removal of the ITS2 spacer; and reorganization of the central protuberance (CP) containing 5S rRNA and r-proteins L5 (uL18) and L11 (uL5). Mutations in the L8 extension block processing of 7S pre-rRNA, prevent release of assembly factors Rpf2 and Rrs1 from pre-ribosomes, which is required for rotation of the CP, and block association of Sda1, the Rix1 complex, and the Rea1 ATPase involved in late steps of remodeling.
authors.affiliation: Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Beril
authors.initials: B
authors.lastname: Tutuncuoglu
authors.affiliation: Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Jelena
authors.initials: J
authors.lastname: Jakovljevic
authors.affiliation: School of Life Sciences, Tsinghua University, Beijing, 100084, China.
authors.forename: Shan
authors.initials: S
authors.lastname: Wu
authors.affiliation: School of Life Sciences, Tsinghua University, Beijing, 100084, China.
authors.forename: Ning
authors.initials: N
authors.lastname: Gao
authors.affiliation: Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA jw17@andrew.cmu.edu.
authors.forename: John L
authors.initials: JL
authors.lastname: Woolford
mesh_terms: D020816:Amino Acid Motifs; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D012335:RNA, Ribosomal / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054683:Ribosome Subunits, Large, Eukaryotic / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; C451023:RPF2 protein, S cerevisiae; C485770:RRS1 protein, S cerevisiae; D012269:Ribosomal Proteins; C496539:Rix1 protein, S cerevisiae; C409685:SDA1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins
keywords: pre-ribosome remodeling; rRNA; ribosomal protein extensions; ribosome assembly