Nucleocytoplasmic Transport of RNAs and RNA–Protein Complexes

Sloan, Katherine E.; Gleizes, Pierre‐Emmanuel; Bohnsack, Markus T.

doi:10.1016/j.jmb.2015.09.023

Cited by 62 publications

(71 citation statements)

References 207 publications

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“…Due to the large size of the pre-40S ribosome, it is predicted that multiple export factors are required to facilitate its rapid translocation [70]. Pre-40S export depends on the GTPase Gsp1/Ran and Crm1/Xpo1, the general exportin for substrates harboring nuclear export signal (NES) sequences [5,10,71,72]. At least three biogenesis factors (Dim2, Ltv1, and Rio2) contain predicted or functional NESs that are, possibly due to their redundancy, individually not required for pre-40S export [5,10].…”

Section: Final Maturation Of Pre-40s Particlesmentioning

confidence: 99%

A Puzzle of Life: Crafting Ribosomal Subunits

Kressler

Hurt

Baßler

2017

Trends in Biochemical Sciences

164

127

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The biogenesis of eukaryotic ribosomes is a complicated process during which the transcription, modification, folding, and processing of the rRNA is coupled with the ordered assembly of $80 ribosomal proteins (r-proteins). Ribosome synthesis is catalyzed and coordinated by more than 200 biogenesis factors as the preribosomal subunits acquire maturity on their path from the nucleolus to the cytoplasm. Several biogenesis factors also interconnect the progression of ribosome assembly with quality control of important domains, ensuring that only functional subunits engage in translation. With the recent visualization of several assembly intermediates by cryoelectron microscopy (cryo-EM), a structural view of ribosome assembly begins to emerge. In this review we integrate these first structural insights into an updated overview of the consecutive ribosome assembly steps. Synopsis of Eukaryotic Ribosome AssemblyRibosomes are the molecular machines that translate the genetic information from the intermediary mRNA templates into proteins [1]. Eukaryotic 80S ribosomes comprise two unequal subunits that contain four different rRNAs and around 80 r-proteins ( Figure 1). The small 40S subunit (SSU) comprises the 18S rRNA and 33 r-proteins (referred to as RPS or S). The large 60S subunit (LSU) comprises the 25S/28S, 5.8S, and 5S rRNA and, in most eukaryotic species, 47 r-proteins (RPL or L); a notable exception is budding yeasts, which lack eL28The act of building a ribosome begins in the nucleolus, where the ribosomal DNA (rDNA) is transcribed into a long pre-rRNA precursor (35S pre-rRNA in yeast) and involves the ordered assembly of the r-proteins with the pre-rRNA, which is concomitantly processed into the mature rRNA species [5][6][7][8] (Figure 1 and Box 1). These assembly and processing events are tightly coupled and occur within preribosomal particles (see Glossary) that travel, as maturation progresses, from the nucleus across nuclear pore complexes (NPCs) to the cytoplasm, where they are ultimately converted into translation-competent ribosomal subunits [5,[9][10][11][12][13] (Figure 2, Key Figure). Given the gargantuan complexity of this process, it is unsurprising that the assembly of eukaryotic ribosomes strictly requires the assistance of a plethora (>200) of mostly essential ribosome biogenesis factors, which are also called trans-acting or assembly factors [5,14,15].Our current knowledge has been mainly obtained by studying ribosome biogenesis in the yeast Saccharomyces cerevisiae. Research conducted in the 1970s defined the r-protein composition of ribosomes, revealed the major pre-rRNA processing intermediates, and uncovered the existence of the 90S, 43S, and 66S preribosomal particles. The following 25 years witnessed the identification of numerous biogenesis factors and attributed functional roles TrendsCryoelectron microscopy analyses of the 90S preribosome show that the biogenesis factors create a casting mold that encloses the nascent pre-40S subunit.Structures of nuclear pre-60S particles reveal that a...

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Section: Final Maturation Of Pre-40s Particlesmentioning

confidence: 99%

A Puzzle of Life: Crafting Ribosomal Subunits

Kressler

Hurt

Baßler

2017

Trends in Biochemical Sciences

164

127

View full text Add to dashboard Cite

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“…Pre-ribosomal particles are transported by multiple transport receptors through nuclear pore complexes (NPCs) into the cytoplasm where they undergo final maturation before initiating translation (Sloan et al, 2016). Cytoplasmic maturation of the 40S pre-ribosome requires endonucleolytic cleavage of the 20S pre-rRNA at site D to generate the 3’ end of mature 18S rRNA.…”

Section: Introductionmentioning

confidence: 99%

Prefabrication of a ribosomal protein subcomplex essential for eukaryotic ribosome formation

Peña

Schütz

Fischer

et al. 2016

eLife

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Spatial clustering of ribosomal proteins (r-proteins) through tertiary interactions is a striking structural feature of the eukaryotic ribosome. However, the functional importance of these intricate inter-connections, and how they are established is currently unclear. Here, we reveal that a conserved ATPase, Fap7, organizes interactions between neighboring r-proteins uS11 and eS26 prior to their delivery to the earliest ribosome precursor, the 90S. In vitro, uS11 only when bound to Fap7 becomes competent to recruit eS26 through tertiary contacts found between these r-proteins on the mature ribosome. Subsequently, Fap7 ATPase activity unloads the uS11:eS26 subcomplex onto its rRNA binding site, and therefore ensures stoichiometric integration of these r-proteins into the 90S. Fap7-depletion in vivo renders uS11 susceptible to proteolysis, and precludes eS26 incorporation into the 90S. Thus, prefabrication of a native-like r-protein subcomplex drives efficient and accurate construction of the eukaryotic ribosome.DOI: http://dx.doi.org/10.7554/eLife.21755.001

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“…It is composed of contiguous subcompartments that collectively generate ribosomal subunits [25–28]. The distribution of yeast nucleolar proteins and rDNA changes dramatically during the cell cycle, finally forming a compact spiral structure as cells enter anaphase [29–35].…”

Section: Resultsmentioning

confidence: 99%

Nucleolar asymmetry and the importance of septin integrity upon cell cycle arrest

2017

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Cell cycle arrest can be imposed by inactivating the anaphase promoting complex (APC). In S. cerevisiae this arrest has been reported to stabilize a metaphase-like intermediate in which the nuclear envelope spans the bud neck, while chromatin repeatedly translocates between the mother and bud domains. The present investigation was undertaken to learn how other features of nuclear organization are affected upon depletion of the APC activator, Cdc20. We observe that the spindle pole bodies and the spindle repeatedly translocate across the narrow orifice at the level of the neck. Nevertheless, we find that the nucleolus (organized around rDNA repeats on the long right arm of chromosome XII) remains in the mother domain, marking the polarity of the nucleus. Accordingly, chromosome XII is polarized: TelXIIR remains in the mother domain and its centromere is predominantly located in the bud domain. In order to learn why the nucleolus remains in the mother domain, we studied the impact of inhibiting rRNA synthesis in arrested cells. We observed that this fragments the nucleolus and that these fragments entered the bud domain. Taken together with earlier observations, the restriction of the nucleolus to the mother domain therefore can be attributed to its massive structure. We also observed that inactivation of septins allowed arrested cells to complete the cell cycle, that the alternative APC activator, Cdh1, was required for completion of the cell cycle and that induction of Cdh1 itself caused arrested cells to progress to the end of the cell cycle.

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Nucleocytoplasmic Transport of RNAs and RNA–Protein Complexes

Cited by 62 publications

References 207 publications

A Puzzle of Life: Crafting Ribosomal Subunits

A Puzzle of Life: Crafting Ribosomal Subunits

Prefabrication of a ribosomal protein subcomplex essential for eukaryotic ribosome formation

Nucleolar asymmetry and the importance of septin integrity upon cell cycle arrest

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