Proofreading of pre-40S ribosome maturation by a translation initiation factor and 60S subunits

Lebaron, Simon; Schneider, Claudia; Nues, Rob W. van; Świątkowska, Agata; Walsh, Dietrich W. M.; Böttcher, Bettina; Granneman, Sander; Watkins, Nicholas J.; Tollervey, David

doi:10.1038/nsmb.2308

Cited by 177 publications

(262 citation statements)

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“…S4A). eIF5B promotes 60S subunit joining in general translation (2, 13) and pre-40S proofreading (15,16). No significant decrease in 80S (eIF5B's function in 60S subunit joining) or 40S [eIF5B's function in pre-40S proofreading (15,16)] levels is observed with eIF5B depletion in serum-starved cells (Fig.…”

Section: Discussionmentioning

confidence: 87%

“…eIF5B is the mammalian ortholog of bacterial IF2 that is important in the formation of the 30S initiation complex, stimulates 50S association to form 70S complexes, and can contribute to stabilizing tRNA-Met i association with the ribosome (2,(11)(12)(13). eIF5B functions in 60S ribosome subunit joining during canonical translation (2,13,14) and is involved in pre-40S ribosome subunit proofing (15,16). eIF5B is also required for the translation of a few viral and specialized mRNAs (12,(17)(18)(19)(20) and can contribute to supporting or stabilizing tRNA-Met i association, including in specific conditions where phosphorylation of the eIF2 subunit, eIF2α, is also observed (12,(17)(18)(19).…”

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confidence: 99%

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Upregulation of eIF5B controls cell-cycle arrest and specific developmental stages

Lee

Truesdell

Bukhari

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Proliferation arrest and distinct developmental stages alter and decrease general translation yet maintain ongoing translation. The factors that support translation in these conditions remain to be characterized. We investigated an altered translation factor in three cell states considered to have reduced general translation: immature Xenopus laevis oocytes, mouse ES cells, and the transition state of proliferating mammalian cells to quiescence (G0) upon growth-factor deprivation. Our data reveal a transient increase of eukaryotic translation initiation factor 5B (eIF5B), the eukaryotic ortholog of bacterial initiation factor IF2, in these conditions. eIF5B promotes 60S ribosome subunit joining and pre-40S subunit proofreading. eIF5B has also been shown to promote the translation of viral and stress-related mRNAs and can contribute indirectly to supporting or stabilizing initiator methionyl tRNA (tRNA-Met i ) association with the ribosome. We find that eIF5B is a limiting factor for translation in these three conditions. The increased eIF5B levels lead to increased eIF5B complexes with tRNA-Met i upon serum starvation of THP1 mammalian cells. In addition, increased phosphorylation of eukaryotic initiation factor 2α, the translation factor that recruits initiator tRNA-Met i for general translation, is observed in these conditions. Importantly, we find that eIF5B is an antagonist of G0 and G0-like states, as eIF5B depletion reduces maturation of G0-like, immature oocytes and hastens early G0 arrest in serumstarved THP1 cells. Consistently, eIF5B overexpression promotes maturation of G0-like immature oocytes and causes cell death, an alternative to G0, in serum-starved THP1 cells. These data reveal a critical role for a translation factor that regulates specific cell-cycle transition and developmental stages.embryonic stem cells | early serum starvation | eIF2α phosphorylation S pecific cell states and transitions, including distinct developmental stages and cell-cycle arrest, alter and decrease general translation (1, 2) yet exhibit ongoing translation (3). In immature Xenopus laevis oocytes, translation of mRNAs is regulated and active after maturation (3, 4); however, mRNAs are translated during immature stages preceding maturation (5). Similarly, canonical translation is altered in mouse ES cells until differentiation (6), but translation ensues in ES cells (7), indicating that uncharacterized factors operate to support general translation in these cell states.The transition from immature to mature oocytes shows some features similar to the entry into mammalian G1/cell cycle from quiescence (G0) (8), an assortment of reversible, cell-cyclearrested states that can withstand unfavorable environments (9). Serum deprivation of proliferating mammalian cells induces an early stage of transient stress that alters gene expression; cells subjected to such stress either adapt to these nonproliferative conditions and proceed further into G0 or alternatively undergo cell death (9). Early (1 day) serum starvation represents...

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Section: Discussionmentioning

confidence: 87%

mentioning

confidence: 99%

Upregulation of eIF5B controls cell-cycle arrest and specific developmental stages

Lee

Truesdell

Bukhari

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…Recruitment of the ATPase Rio1, presumably requiring the prior dissociation of Tsr1 [78], yields late pre-40S ribosomes that are competent to join 60S subunits [79][80][81]. Within these 80S-like ribosomes, Rio1 and the GTPase eIF5B stimulate the Nob1-catalyzed cleavage at site D of the 20S pre-rRNA into mature 18S rRNA [74,80,[82][83][84] (Figures 1 and 2H). Coupling pre-40S maturation to such a quality control step ensures that only properly assembled 40S subunits enter the pool of translating 80S ribosomes.…”

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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“…Two consecutive steps of ribosome biogenesis, namely Tif6 release by the Efl1 GTPase and the "translation-like cycle" catalyzed by the eIF5B, might be GAC dependent. 28,29 Based on sequence homology, high-resolution structures, and previous biochemical data, it is tempting to assume that the mode of functioning of Efl1 and eIF5B is similar to other trGTPases (e.g. eEF2 or eEF1A), and consequently uL11 dependent.…”

Section: Introductionmentioning

confidence: 99%

Functional analysis of the uL11 protein impact on translational machinery

Wawiórka¹,

Molestak²,

Szajwaj³

et al. 2016

Cell Cycle

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The ribosomal GTPase associated center constitutes the ribosomal area, which is the landing platform for translational GTPases and stimulates their hydrolytic activity. The ribosomal stalk represents a landmark structure in this center, and in eukaryotes is composed of uL11, uL10 and P1/P2 proteins. The modus operandi of the uL11 protein has not been exhaustively studied in vivo neither in prokaryotic nor in eukaryotic cells. Using a yeast model, we have brought functional insight into the translational apparatus deprived of uL11, filling the gap between structural and biochemical studies. We show that the uL11 is an important element in various aspects of 'ribosomal life'. uL11 is involved in 'birth' (biogenesis and initiation), by taking part in Tif6 release and contributing to ribosomal subunit-joining at the initiation step of translation. uL11 is particularly engaged in the 'active life' of the ribosome, in elongation, being responsible for the interplay with eEF1A and fidelity of translation and contributing to a lesser extent to eEF2-dependent translocation. Our results define the uL11 protein as a critical GAC element universally involved in trGTPase 'productive state' stabilization, being primarily a part of the ribosomal element allosterically contributing to the fidelity of the decoding event.

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Proofreading of pre-40S ribosome maturation by a translation initiation factor and 60S subunits

Cited by 177 publications

References 56 publications

Upregulation of eIF5B controls cell-cycle arrest and specific developmental stages

Upregulation of eIF5B controls cell-cycle arrest and specific developmental stages

A Puzzle of Life: Crafting Ribosomal Subunits

Functional analysis of the uL11 protein impact on translational machinery

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