Defining the Pathway of Cytoplasmic Maturation of the 60S Ribosomal Subunit

• DOI: 10.1016/j.molcel.2010.06.018
• Publication Date: 2010-07-30T08:19:49Z
• Authors: Kai-Yin Lo; Zhihua Li; Cyril Bussiere; Stefan Bresson; Edward M. Marcotte; Arlen W. Johnson
• Keywords: Adenosine Triphosphatases; Ribosomal Proteins; 0301 basic medicine; Cytoplasm; Saccharomyces cerevisiae Proteins; RNA-Binding Proteins; Cell Biology; Saccharomyces cerevisiae; Ribosome Subunits, Large, Eukaryotic; GTP Phosphohydrolases; 03 medical and health sciences; GTP-Binding Proteins; Protein Biosynthesis; Humans; Molecular Biology; HeLa Cells

In eukaryotic cells the final maturation of ribosomes occurs in the cytoplasm, where trans-acting factors are removed and critical ribosomal proteins are added for functionality. Here, we have carried out a comprehensive analysis of cytoplasmic maturation, ordering the known steps into a coherent pathway. Maturation is initiated by the ATPase Drg1. Downstream, assembly of the ribosome stalk is essential for the release of Tif6. The stalk recruits GTPases during translation. Because the GTPase Efl1, which is required for the release of Tif6, resembles the translation elongation factor eEF2, we suggest that assembly of the stalk recruits Efl1, triggering a step in 60S biogenesis that mimics aspects of translocation. Efl1 could thereby provide a mechanism to functionally check the nascent subunit. Finally, the release of Tif6 is a prerequisite for the release of the nuclear export adaptor Nmd3. Establishing this pathway provides an important conceptual framework for understanding ribosome maturation.