Synchronizing Nuclear Import of Ribosomal Proteins with Ribosome Assembly

• Published in: Science (American Association for the Advancement of Science) 2012-11, Vol.338 (6107), p.666-671
• Main Authors: Kressler, Dieter, Bange, Gert, Ogawa, Yutaka, Stjepanovic, Goran, Bradatsch, Bettina, Pratte, Dagmar, Amlacher, Stefan, Strauß, Daniela, Yoneda, Yoshihiro, Katahira, Jun, Sinning, Irmgard, Hurt, Ed
• Format: Article
• Language: English
• Subjects: Active Transport, Cell Nucleus; Amino Acid Sequence; Analytical, structural and metabolic biochemistry; Assembly; Base Sequence; beta Karyopherins - metabolism; Binding; Biological and medical sciences; Biosynthesis; Cell Nucleus - metabolism; Cellular biology; Chaetomium - metabolism; Chromatography; Crystallography, X-Ray; Cytoplasm; Fundamental and applied biological sciences. Psychology; Fungal Proteins - chemistry; Fungal Proteins - metabolism; HeLa cells; Imports; Models, Molecular; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; Molecular weight; Nuclear pore complex proteins; Nuclei; Polyribosomes; Protein Binding; Protein Conformation; Protein Multimerization; Protein Structure, Tertiary; Protein synthesis; Proteins; Receptors; Ribosomal DNA; Ribosomal Proteins - chemistry; Ribosomal Proteins - metabolism; Ribosomes; Ribosomes - metabolism; RNA, Fungal - metabolism; RNA, Ribosomal, 5S - metabolism; RNA-Binding Proteins - chemistry; RNA-Binding Proteins - metabolism; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - metabolism; Synchronous; Translation. Translation factors. Protein processing; Transport; Yeasts
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1226960

Ribosomal proteins are synthesized in the cytoplasm, before nuclear import and assembly with ribosomal RNA (rRNA). Little is known about coordination of nucleocytoplasmic transport with ribosome assembly. Here, we identify a transport adaptor, symportin 1 (Syo1), that facilitates synchronized coimport of the two 5S-rRNA binding proteins Rpl5 and Rpl11. In vitro studies revealed that Syo1 concomitantly binds Rpl5-Rpl11 and furthermore recruits the import receptor Kap104. The Syo1-Rpl5-Rpl11 import complex is released from Kap104 by RanGTP and can be directly transferred onto the 5S rRNA. Syo1 can shuttle back to the cytoplasm by interaction with phenylalanine-glycine nucleoporins. X-ray crystallography uncovered how the α-solenoid symportin accommodates the Rpl5 amino terminus, normally bound to 5S rRNA, in an extended groove. Symportin-mediated coimport of Rpl5-Rpl11 could ensure coordinated and stoichiometric incorporation of these proteins into pre-60S ribosomes.