Recent studies implicate the nucleolus as the major site of nuclear translation

2014 ◽  
Vol 42 (4) ◽  
pp. 1224-1228 ◽  
Author(s):  
Tina McLeod ◽  
Akilu Abdullahi ◽  
Min Li ◽  
Saverio Brogna
Keyword(s):  
Ribosomal Rna ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Nuclear Protein ◽  
Substantial Evidence ◽  
Major Site ◽  
Ribosomal Subunits ◽  
Late Maturation ◽  
Mrna Binding ◽  
Nuclear Translation

The nucleolus is the most prominent morphological feature within the nucleus of eukaryotic cells and is best known for its role in ribosome biogenesis. It forms around highly transcribed ribosomal RNA gene repeats which yield precursor rRNAs that are co-transcriptionally processed, folded and, while still within the nucleolus, associate with most of the ribosomal proteins. The nucleolus is therefore often thought of as a factory for making ribosomal subunits, which are exported as inactive precursors to the cytoplasm where late maturation makes them capable of mRNA binding and translation initiation. However, recent studies have shown substantial evidence for the presence of functional, translation competent ribosomal subunits within the nucleus, particularly in the nucleolus. These observations raise the intriguing possibility that the nucleolus, as well as being a ribosome factory, is also an important nuclear protein-synthesis plant.

scholarly journals The nucleolar DExD/H protein Hel66 is involved in ribosome biogenesis in Trypanosoma brucei

2021 ◽  
Author(s):  
Majeed Bakari-Soale ◽  
Nonso Josephat Ikenge ◽  
Marion Scheibe ◽  
Falk Butter ◽  
Nicola Gail Jones ◽  
...  
Keyword(s):  
Ribosomal Rna ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Growth Defect ◽  
Rrna Processing ◽  
Ribosomal Subunits ◽  
Comprehensive Picture ◽  
Severe Growth Defect ◽  
H Protein ◽  
Severe Growth

The biosynthesis of ribosomes is a complex cellular process involving ribosomal RNA, ribosomal proteins and several further trans-acting factors. DExD/H box proteins constitute the largest family of trans-acting protein factors involved in this process. Several members of this protein family have been directly implicated in ribosome biogenesis in yeast. In trypanosomes, ribosome biogenesis differs in several features from the process described in yeast. Here, we have identified the DExD/H box helicase Hel66 as being involved in ribosome biogenesis. The protein is unique to Kinetoplastida, localises to the nucleolus and its depletion via RNAi caused a severe growth defect. Loss of the protein resulted in a decrease of global translation and accumulation of rRNA processing intermediates for both the small and large ribosomal subunits. Only a few factors involved in trypanosome rRNA biogenesis have been described so far and our findings contribute to gaining a more comprehensive picture of this essential process.

scholarly journals The Nucleolar DExD/H Protein Hel66 is Involved in Ribosome Biogenesis in Trypanosoma Brucei

2021 ◽  
Author(s):  
Majeed Bakari-Soale ◽  
Nonso Josephat Ikenga ◽  
Marion Scheibe ◽  
Falk Butter ◽  
Nicola Gail Jones ◽  
...  
Keyword(s):  
Ribosomal Rna ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Growth Defect ◽  
Rrna Processing ◽  
Ribosomal Subunits ◽  
Comprehensive Picture ◽  
Severe Growth Defect ◽  
H Protein ◽  
Severe Growth

Abstract The biosynthesis of ribosomes is a complex cellular process involving ribosomal RNA, ribosomal proteins and several further trans-acting factors. DExD/H box proteins constitute the largest family of trans-acting protein factors involved in this process. Several members of this protein family have been directly implicated in ribosome biogenesis in yeast. In trypanosomes, ribosome biogenesis differs in several features from the process described in yeast. Here, we have identified the DExD/H box helicase Hel66 as being involved in ribosome biogenesis. The protein is unique to Kinetoplastida, localises to the nucleolus and its depletion via RNAi caused a severe growth defect. Loss of the protein resulted in a decrease of global translation and accumulation of rRNA processing intermediates for both the small and large ribosomal subunits. Only a few factors involved in trypanosome rRNA biogenesis have been described so far and our findings contribute to gaining a more comprehensive picture of this essential process.

scholarly journals The nucleolar DExD/H protein Hel66 is involved in ribosome biogenesis in Trypanosoma brucei

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Majeed Bakari-Soale ◽  
Nonso Josephat Ikenga ◽  
Marion Scheibe ◽  
Falk Butter ◽  
Nicola G. Jones ◽  
...  
Keyword(s):  
Ribosomal Rna ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Growth Defect ◽  
Rrna Processing ◽  
Ribosomal Subunits ◽  
Comprehensive Picture ◽  
Severe Growth Defect ◽  
H Protein ◽  
Severe Growth

AbstractThe biosynthesis of ribosomes is a complex cellular process involving ribosomal RNA, ribosomal proteins and several further trans-acting factors. DExD/H box proteins constitute the largest family of trans-acting protein factors involved in this process. Several members of this protein family have been directly implicated in ribosome biogenesis in yeast. In trypanosomes, ribosome biogenesis differs in several features from the process described in yeast. Here, we have identified the DExD/H box helicase Hel66 as being involved in ribosome biogenesis. The protein is unique to Kinetoplastida, localises to the nucleolus and its depletion via RNAi caused a severe growth defect. Loss of the protein resulted in a decrease of global translation and accumulation of rRNA processing intermediates for both the small and large ribosomal subunits. Only a few factors involved in trypanosome rRNA biogenesis have been described so far and our findings contribute to gaining a more comprehensive picture of this essential process.

Control points in eucaryotic ribosome biogenesis

1991 ◽  
Vol 69 (1) ◽  
pp. 5-22 ◽  
Author(s):  
D. E. Larson ◽  
P. Zahradka ◽  
B. H. Sells
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Rna Polymerase Iii ◽  
Ribosomal Subunits ◽  
Rrna Species ◽  
Polymerase I ◽  
Ribosomal Precursor ◽  
Precursor Molecules

Ribosome biogenesis in eucaryotic cells involves the coordinated synthesis of four rRNA species, transcribed by RNA polymerase I (18S, 28S, 5.8S) and RNA polymerase III (5S), and approximately 80 ribosomal proteins translated from mRNAs synthesized by RNA polymerase II. Assembly of the ribosomal subunits in the nucleolus, the site of 45S rRNA precursor gene transcription, requires the movement of 5S rRNA and ribosomal proteins from the nucleoplasm and cytoplasm, respectively, to this structure. To integrate these events and ensure the balanced production of individual ribosomal components, different strategies have been developed by eucaryotic organisms in response to a variety of physiological changes. This review presents an overview of the mechanisms modulating the production of ribosomal precursor molecules and the rate of ribosome biogenesis in various biological systems.Key words: rRNA, ribosomal proteins, nucleolus, ribosome.

Eukaryotic Ribosome Assembly

2019 ◽  
Vol 88 (1) ◽  
pp. 281-306 ◽  
Author(s):  
Jochen Baßler ◽  
Ed Hurt
Keyword(s):  
Ribosomal Rna ◽  
Nuclear Export ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Cryo Electron Microscopy ◽  
A Cell ◽  
Cellular Pathways ◽  
Nucleolar Rnas ◽  
Shed Light

Ribosomes, which synthesize the proteins of a cell, comprise ribosomal RNA and ribosomal proteins, which coassemble hierarchically during a process termed ribosome biogenesis. Historically, biochemical and molecular biology approaches have revealed how preribosomal particles form and mature in consecutive steps, starting in the nucleolus and terminating after nuclear export into the cytoplasm. However, only recently, due to the revolution in cryo–electron microscopy, could pseudoatomic structures of different preribosomal particles be obtained. Together with in vitro maturation assays, these findings shed light on how nascent ribosomes progress stepwise along a dynamic biogenesis pathway. Preribosomes assemble gradually, chaperoned by a myriad of assembly factors and small nucleolar RNAs, before they reach maturity and enter translation. This information will lead to a better understanding of how ribosome synthesis is linked to other cellular pathways in humans and how it can cause diseases, including cancer, if disturbed.

scholarly journals Intranucleolar sites of ribosome biogenesis defined by the localization of early binding ribosomal proteins

2007 ◽  
Vol 177 (4) ◽  
pp. 573-578 ◽  
Author(s):  
Tim Krüger ◽  
Hanswalter Zentgraf ◽  
Ulrich Scheer
Keyword(s):  
Ribosomal Rna ◽  
Ribosomal Proteins ◽  
Live Cell Imaging ◽  
Ribosome Biogenesis ◽  
Cell Imaging ◽  
Rrna Processing ◽  
Dense Fibrillar Component ◽  
Assembly Pathway ◽  
Fibrillar Component ◽  
Processing Steps

Considerable efforts are being undertaken to elucidate the processes of ribosome biogenesis. Although various preribosomal RNP complexes have been isolated and molecularly characterized, the order of ribosomal protein (r-protein) addition to the emerging ribosome subunits is largely unknown. Furthermore, the correlation between the ribosome assembly pathway and the structural organization of the dedicated ribosome factory, the nucleolus, is not well established. We have analyzed the nucleolar localization of several early binding r-proteins in human cells, applying various methods, including live-cell imaging and electron microscopy. We have located all examined r-proteins (S4, S6, S7, S9, S14, and L4) in the granular component (GC), which is the nucleolar region where later pre-ribosomal RNA (rRNA) processing steps take place. These results imply that early binding r-proteins do not assemble with nascent pre-rRNA transcripts in the dense fibrillar component (DFC), as is generally believed, and provide a link between r-protein assembly and the emergence of distinct granules at the DFC–GC interface.

scholarly journals Association of snR190 snoRNA chaperone with early pre-60S particles is regulated by the RNA helicase Dbp7 in yeast

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Mariam Jaafar ◽  
Julia Contreras ◽  
Carine Dominique ◽  
Sara Martín-Villanueva ◽  
Régine Capeyrou ◽  
...  
Keyword(s):  
Ribosomal Rna ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Ribosomal Subunit ◽  
Rna Helicase ◽  
Genetic Interactions ◽  
Large Ribosomal Subunit ◽  
Base Pairing ◽  
Peptidyl Transferase ◽  
Peptidyl Transferase Center

AbstractSynthesis of eukaryotic ribosomes involves the assembly and maturation of precursor particles (pre-ribosomal particles) containing ribosomal RNA (rRNA) precursors, ribosomal proteins (RPs) and a plethora of assembly factors (AFs). Formation of the earliest precursors of the 60S ribosomal subunit (pre-60S r-particle) is among the least understood stages of ribosome biogenesis. It involves the Npa1 complex, a protein module suggested to play a key role in the early structuring of the pre-rRNA. Npa1 displays genetic interactions with the DExD-box protein Dbp7 and interacts physically with the snR190 box C/D snoRNA. We show here that snR190 functions as a snoRNA chaperone, which likely cooperates with the Npa1 complex to initiate compaction of the pre-rRNA in early pre-60S r-particles. We further show that Dbp7 regulates the dynamic base-pairing between snR190 and the pre-rRNA within the earliest pre-60S r-particles, thereby participating in structuring the peptidyl transferase center (PTC) of the large ribosomal subunit.

scholarly journals The Arabidopsis 2′-O-Ribose-Methylation and Pseudouridylation Landscape of rRNA in Comparison to Human and Yeast

2021 ◽  
Vol 12 ◽  
Author(s):  
Deniz Streit ◽  
Enrico Schleiff
Keyword(s):  
Arabidopsis Thaliana ◽  
Ribosomal Rna ◽  
Ribosomal Dna ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Ribosome Assembly ◽  
Small Nucleolar Rnas ◽  
General Process ◽  
Specific Factors ◽  
Nucleolar Rnas

Eukaryotic ribosome assembly starts in the nucleolus, where the ribosomal DNA (rDNA) is transcribed into the 35S pre-ribosomal RNA (pre-rRNA). More than two-hundred ribosome biogenesis factors (RBFs) and more than two-hundred small nucleolar RNAs (snoRNA) catalyze the processing, folding and modification of the rRNA in Arabidopsis thaliana. The initial pre-ribosomal 90S complex is formed already during transcription by association of ribosomal proteins (RPs) and RBFs. In addition, small nucleolar ribonucleoprotein particles (snoRNPs) composed of snoRNAs and RBFs catalyze the two major rRNA modification types, 2′-O-ribose-methylation and pseudouridylation. Besides these two modifications, rRNAs can also undergo base methylations and acetylation. However, the latter two modifications have not yet been systematically explored in plants. The snoRNAs of these snoRNPs serve as targeting factors to direct modifications to specific rRNA regions by antisense elements. Today, hundreds of different sites of modifications in the rRNA have been described for eukaryotic ribosomes in general. While our understanding of the general process of ribosome biogenesis has advanced rapidly, the diversities appearing during plant ribosome biogenesis is beginning to emerge. Today, more than two-hundred RBFs were identified by bioinformatics or biochemical approaches, including several plant specific factors. Similarly, more than two hundred snoRNA were predicted based on RNA sequencing experiments. Here, we discuss the predicted and verified rRNA modification sites and the corresponding identified snoRNAs on the example of the model plant Arabidopsis thaliana. Our summary uncovers the plant modification sites in comparison to the human and yeast modification sites.

NSR1 is required for pre-rRNA processing and for the proper maintenance of steady-state levels of ribosomal subunits

1992 ◽  
Vol 12 (9) ◽  
pp. 3865-3871
Author(s):  
W C Lee ◽  
D Zabetakis ◽  
T Mélèse
Keyword(s):  
Nuclear Localization ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Protein Translation ◽  
Striking Similarity ◽  
Growth Defect ◽  
Nuclear Localization Sequence ◽  
Rrna Processing ◽  
Ribosomal Subunits ◽  
Localization Sequence

NSR1 is a yeast nuclear localization sequence-binding protein showing striking similarity in its domain structure to nucleolin. Cells lacking NSR1 are viable but have a severe growth defect. We show here that NSR1, like nucleolin, is involved in ribosome biogenesis. The nsr1 mutant is deficient in pre-rRNA processing such that the initial 35S pre-rRNA processing is blocked and 20S pre-rRNA is nearly absent. The reduced amount of 20S pre-rRNA leads to a shortage of 18S rRNA and is reflected in a change in the distribution of 60S and 40S ribosomal subunits; there is no free pool of 40S subunits, and the free pool of 60S subunits is greatly increased in size. The lack of free 40S subunits or the improper assembly of these subunits causes the nsr1 mutant to show sensitivity to the antibiotic paromomycin, which affects protein translation, at concentrations that do not affect the growth of the wild-type strain. Our data support the idea that NSR1 is involved in the proper assembly of pre-rRNA particles, possibly by bringing rRNA and ribosomal proteins together by virtue of its nuclear localization sequence-binding domain and multiple RNA recognition motifs. Alternatively, NSR1 may also act to regulate the nuclear entry of ribosomal proteins required for proper assembly of pre-rRNA particles.

scholarly journals Principles of 60S ribosomal subunit assembly emerging from recent studies in yeast

2017 ◽  
Vol 474 (2) ◽  
pp. 195-214 ◽  
Author(s):  
Salini Konikkat ◽  
John L. Woolford,
Keyword(s):  
Ribosomal Rna ◽  
Ribosomal Proteins ◽  
Ribosome Biogenesis ◽  
Ribosomal Subunit ◽  
Ribosome Assembly ◽  
Small Nucleolar Rnas ◽  
Large Ribosomal Subunit ◽  
Yeast Saccharomyces Cerevisiae ◽  
Subunit Assembly ◽  
Nucleolar Rnas

Ribosome biogenesis requires the intertwined processes of folding, modification, and processing of ribosomal RNA, together with binding of ribosomal proteins. In eukaryotic cells, ribosome assembly begins in the nucleolus, continues in the nucleoplasm, and is not completed until after nascent particles are exported to the cytoplasm. The efficiency and fidelity of ribosome biogenesis are facilitated by >200 assembly factors and ∼76 different small nucleolar RNAs. The pathway is driven forward by numerous remodeling events to rearrange the ribonucleoprotein architecture of pre-ribosomes. Here, we describe principles of ribosome assembly that have emerged from recent studies of biogenesis of the large ribosomal subunit in the yeast Saccharomyces cerevisiae. We describe tools that have empowered investigations of ribosome biogenesis, and then summarize recent discoveries about each of the consecutive steps of subunit assembly.

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