Roles of Eukaryotic Ribosomal Proteins in Maturation and Transport of Pre-18S rRNA and Ribosome Function

Abstract

Despite the rising knowledge about ribosome function and structure and how ribosomal subunits assemble in vitro in bacteria, the in vivo role of many ribosomal proteins remains obscure both in pro- and eukaryotes. Our systematic analysis of yeast ribosomal proteins (r-proteins) of the small subunit revealed that most eukaryotic r-proteins fulfill different roles in ribosome biogenesis, making them indispensable for growth. Different r-proteins control distinct steps of nuclear and cytoplasmic pre-18S rRNA processing and, thus, ensure that only properly assembled ribosomes become engaged in translation. Comparative analysis of dynamic and steady-state maturation assays revealed that several r-proteins are required for efficient nuclear export of pre-18S rRNA, suggesting that they form an interaction platform with the export machinery. In contrast, the presence of other r-proteins is mainly required before nuclear export is initiated. Our studies draw a correlation between the in vitro assembly, structural localization, and in vivo function of r-proteins.

A hierarchical model for assembly of eukaryotic 60S ribosomal subunit domains

“…It has become increasingly apparent that the hierarchical assembly of small ribosomal subunit domains is largely conserved from bacteria to eukaryotes (Held et al 1974;Ferreira-Cerca et al 2005Mulder et al 2010;O'Donohue et al 2010;Chen and Williamson 2013;Clatterbuck Soper et al 2013). What remained unclear is whether the same is true for large ribosomal subunits.…”

“…RP depletions in yeast and siRNA-mediated knockdowns in cultured mammalian cells showed that most RPs are essential for ribosome biogenesis (Ferreira-Cerca et al 2005;Robledo et al 2008;Poll et al 2009;Babiano and de la Cruz 2010;O'Donohue et al 2010;Jakovljevic et al 2012;Gamalinda et al 2013). However, phenotypic analyses of these mutants were primarily limited to assaying effects on pre-rRNA processing and nucleocytoplasmic export of preribosomes.…”

“…The segregation of large subunits into distinct structural domains is not as apparent as for small subunits (Ban et al 2000); the six rRNA domains are more intertwined in large subunits (Holbrook 2008). Hence, it was initially striking to find that depletion of individual yeast large subunit RPs (RPLs) led to specific rather than global pre-rRNA processing defects (Ferreira-Cerca et al 2005;Hofer et al 2007;Robledo et al 2008;Poll et al 2009; Fernandez-Pevida et al 2012;Jakovljevic et al 2012;Gamalinda et al 2013), which are grouped into early, middle, and late classes (Table 1). From these results, we observed a pattern previously not described: RPLs belonging to these phenotypic classes are remarkably clustered into distinct structural neighborhoods of the yeast 60S subunit ( Fig.…”

Qu’en est-il de la biogenèse des ribosomes chez l’homme ?

“…Un système de contrôle de cette maturation est assuré en partie par l'assemblage de protéines ribosomiques. Ainsi, la petite sous-unité n'est exportée du noyau que lorsque les protéines RPS15/RPS18 (selon la nouvelle nomenclature, uS19/uS13, [21]) et RPS5/RPS28 (eS25/eS28) sont assemblées sur la particule [22,23].…”

Giant panda ribosomal protein S14: cDNA, genomic sequence cloning, sequence analysis, and overexpression

“…The small subunit protein RPS14, the yeast homolog of the bacterial S11 protein, directly binds helix 23 of 18S rRNA (Fewell and Woolford Jr., 1999;Mayolo and Woolford Jr., 2003). Recently, it was reported that RPS14 is an essential protein necessary for the maturation of the 40S ribosomal subunit (Larkin et al, 1987;Moritz et al, 1990;Paulovich et al, 1993;Ford et al, 1999;Jakovljevic et al, 2004) and the processing of 18S pre-rRNA (Ferreira-Cerca et al, 2005;Ebert et al, 2008). And in the 40S subunit, RPS14 helps to form the mRNA exit channel along with its interacting protein RPS5 (Yusupov et al, 2001).…”