Eukaryotic Ribosome Assembly Research Articles

An inventory of yeast proteins associated with nucleolar and ribosomal components

Phylogenetic profiling and gene expression analysis of yeast proteins suggests that the nucleolus probably evolved from an archaeal-type ribosome maturation machinery by recruitment of several bacterial-type and mostly eukaryote-specific factors

Recent developments in factor-facilitated ribosome assembly

Escherichia coli ribosomal subunits can be reconstituted in vitro under highly optimized conditions. These reconstitution systems have proven invaluable for the study of ribosomal subunit assembly. While E. coli ribosomal subunits can self-assemble in vitro there has been much speculation regarding the existence of extra-ribosomal assembly factors that act in functional subunit formation in vivo. Recently, a biochemical assay has been implemented to identify factors that facilitate a single, critical step in 30S subunit assembly in vitro. These studies have revealed that the DnaK (heat shock protein 70) chaperone system can facilitate 30S subunit assembly in vitro. The 30S subunits, formed in the presence of the chaperones under otherwise non-permissive conditions, are highly similar to 30S subunits formed under standard reconstitution conditions. It has become evident that the manner in which the “factor-assembled” 30S subunits are purified is critical for monitoring formation of functional ribosomal particles. Given that methodologies for in vitro reconstitution and functional analysis of ribosomal subunits have been described in detail previously, this manuscript will focus on isolation of functional 30S subunits that have been assembled in the presence of exogenous factors in vitro. Also, recent efforts toward understanding the roles of exogenous factors in 50S subunit and eukaryotic ribosome assembly will be briefly discussed.

Functional Inactivation of the Mouse Nucleolar Protein Bop1 Inhibits Multiple Steps in Pre-rRNA Processing and Blocks Cell Cycle Progression

Bop1 is a conserved nucleolar protein involved in rRNA processing and ribosome assembly in eukaryotes. Expression of its dominant-negative mutant Bop1 Delta in mouse cells blocks rRNA maturation and synthesis of large ribosomal subunits and induces a reversible, p53-dependent cell cycle arrest. In this study, we have conducted a deletion analysis of Bop1 and identified a new mutant, Bop1N2, that also acts as a potent inhibitor of cell cycle progression. Bop1N2 and Bop1 Delta are C-terminal and N-terminal deletion mutants, respectively, and share only 72 amino acid residues. Both mutant proteins are localized to the nucleolus and strongly inhibit rRNA processing, suggesting that activation of a cell cycle checkpoint by Bop1 mutants is linked to their inhibitory effects on rRNA and ribosome synthesis. By using these dominant-negative mutants as well as antisense oligonucleotides to interfere with endogenous Bop1, we identified specific rRNA processing steps that require Bop1 function in mammalian cells. Our data demonstrate that Bop1 is required for proper processing at four distinct sites located within the internal transcribed spacers ITS1 and ITS2 and the 3' external spacer. We propose a model in which Bop1 serves as an essential factor in ribosome formation that coordinates processing of the spacer regions in pre-rRNA.

Subcellular distribution of ribosomal proteins S6 and eL12. Analysis by autoradiography and immunofluorescence of sections from oocytes of Xenopus laevis.

The process of ribosome assembly in eukaryotes was studied by injecting tritium-labeled ribosomal proteins S6 and eL12 into oocytes of Xenopus laevis. The subcellular distribution of the two proteins was visualized by means of autoradiography in sections of oocytes. Protein S6 but not eL12 was found in the nucleus where it accumulated at the nucleoli. In the presence of actinomycin D the accumulation of S6 at the nucleoli was reduced. In-situ immunofluorescence studies indicated that S6 is located at the nucleoli and eL12 exclusively in the cytoplasm. It appears that S6 is involved in the early ribosomal assembly process at the nucleoli, whereas eL12 is restricted to the cytoplasm where it is incorporated into 60S ribosomal subunits in a late assembly step.

Ribosomal proteins and the assembly of ribosomes in eukaryotes.

Research Article| September 01 1972 Ribosomal proteins and the assembly of ribosomes in eukaryotes J R Warner; J R Warner Search for other works by this author on: This Site PubMed Google Scholar A Kumar; A Kumar Search for other works by this author on: This Site PubMed Google Scholar S A Udem; S A Udem Search for other works by this author on: This Site PubMed Google Scholar R S Wu R S Wu Search for other works by this author on: This Site PubMed Google Scholar Biochem J (1972) 129 (3): 29P–30P. https://doi.org/10.1042/bj1290029P Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Cite Icon Cite Get Permissions Citation J R Warner, A Kumar, S A Udem, R S Wu; Ribosomal proteins and the assembly of ribosomes in eukaryotes. Biochem J 1 September 1972; 129 (3): 29P–30P. doi: https://doi.org/10.1042/bj1290029P Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsBiochemical Journal Search Advanced Search This content is only available as a PDF. © 1972 London: The Biochemical Society1972 Article PDF first page preview Close Modal You do not currently have access to this content.