1. Diverse roles of assembly factors revealed by structures of late nuclear pre-60S ribosomes
- Author
-
Dan Tan, Jianlin Lei, Hailey Brown, Shan Wu, Zhifei Li, Yixiao Zhang, Ning Gao, Chengying Ma, John L. Woolford, Meng-Qiu Dong, Beril Tutuncuoglu, Jelena Jakovljevic, Yi Yuan, Kaige Yan, and Michael Gamalinda
- Subjects
0301 basic medicine ,Models, Molecular ,Ribosomal Proteins ,Cytoplasm ,Saccharomyces cerevisiae Proteins ,Rotation ,Nucleolus ,Molecular Sequence Data ,Active Transport, Cell Nucleus ,Ribosome biogenesis ,Saccharomyces cerevisiae ,Biology ,Ribosome ,Article ,GTP Phosphohydrolases ,03 medical and health sciences ,Ribosomal protein ,GTP-Binding Proteins ,Catalytic Domain ,DNA, Ribosomal Spacer ,Nuclear export signal ,Genetics ,Cell Nucleus ,Multidisciplinary ,Base Sequence ,Eukaryotic Large Ribosomal Subunit ,Cryoelectron Microscopy ,Nuclear Proteins ,RNA, Fungal ,Ribosome Subunits, Large, Eukaryotic ,Cell biology ,030104 developmental biology ,Ribonucleoproteins ,Ribosome Subunits ,RNA, Ribosomal ,Eukaryotic Ribosome ,Protein Binding - Abstract
Ribosome biogenesis is a highly complex process in eukaryotes, involving temporally and spatially regulated ribosomal protein (r-protein) binding and ribosomal RNA remodelling events in the nucleolus, nucleoplasm and cytoplasm1,2. Hundreds of assembly factors, organized into sequential functional groups3,4, facilitate and guide the maturation process into productive assembly branches in and across different cellular compartments. However, the precise mechanisms by which these assembly factors function are largely unknown. Here we use cryo-electron microscopy to characterize the structures of yeast nucleoplasmic pre-60S particles affinity-purified using the epitope-tagged assembly factor Nog2. Our data pinpoint the locations and determine the structures of over 20 assembly factors, which are enriched in two areas: an arc region extending from the central protuberance to the polypeptide tunnel exit, and the domain including the internal transcribed spacer 2 (ITS2) that separates 5.8S and 25S ribosomal RNAs. In particular, two regulatory GTPases, Nog2 and Nog1, act as hub proteins to interact with multiple, distant assembly factors and functional ribosomal RNA elements, manifesting their critical roles in structural remodelling checkpoints and nuclear export. Moreover, our snapshots of compositionally and structurally different pre-60S intermediates provide essential mechanistic details for three major remodelling events before nuclear export: rotation of the 5S ribonucleoprotein, construction of the active centre and ITS2 removal. The rich structural information in our structures provides a framework to dissect molecular roles of diverse assembly factors in eukaryotic ribosome assembly.
- Published
- 2015