eIF2B-catalyzed nucleotide exchange and phosphoregulation by the integrated stress response

Kenner, L.R.; Anand, Aditya; Nguyen, Henry C.; Myasnikov, Alexander; Klose, Carolin J.; McGeever, Lea A.; Tsai, Jordan C.; Miller-Vedam, Lakshmi E.; Walter, Peter; Frost, Adam

doi:10.1126/science.aaw2922

Cited by 109 publications

(185 citation statements)

References 43 publications

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“…Noteworthy, the eIF5-CTD shares a common topology with the CTD of the ε subunit of the nucleotide exchange factor eIF2B (16); they both fold into a W2-type HEAT domain (27) mediating contacts of both factors with the eIF2β-NTT and eIF2γ (31). Based on our structure, the arrangement of the eIF5-CTD HEAT domain binding site on eIF2γ in the context of the 43S PIC is similar to that of the eIF2Bε-CTD HEAT domain in the context of the recently solved eIF2-eIF2B complex (32,33).…”

Section: The Eif5 C-terminal Domain (Ctd) In the Context Of The 43s Picsupporting

confidence: 58%

Structural differences in translation initiation between pathogenic trypanosomatids and their mammalian hosts

Bochler

Querido

Prilepskaja

et al. 2019

Preprint

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The 43S pre-initiation complex (PIC) assembly requires establishment of numerous interactions among eukaryotic initiation factors (eIFs), Met-tRNA i Met and the small ribosomal subunit (40S). Owing to several differences in the structure and composition of kinetoplastidian 40S compared to their mammalian counterparts, translation initiation in trypanosomatids is suspected to display substantial variability. Here, we determined the structure of the 43S PIC from Trypanosoma cruzi, the Chagas disease parasite, showing numerous specific features, such as different eIF3 structure and interactions with the large rRNA expansion segments 9 S , 7 S and 6 S , and the association of a kinetoplastid-specific ~245 kDa DDX60-like helicase. We also revealed a previously undetermined binding site of the eIF5 C-terminal domain, and terminal tails of eIF2β, eIF1, eIF1A and eIF3 c and d subunits, uncovering molecular details of their critical activities.One Sentence Summary: The 43S pre-initiation complex structure from Trypanosoma cruzi reveals kinetoplastid-specific features of translation initiation. Main Text:The first critical initiation step in eukaryotes is the assembly of the 43S PIC comprising the 40S, the eIF2•GTP•Met-tRNAi Met ternary complex, and eIFs 1, 1A, 3 and 5 (1, 2). It is followed by the recruitment of the mRNA promoted by the mRNA cap-binding complex comprising eIF4A, 4B and 4F (3, 4), forming the 48S PIC. The 48S PIC then scans the 5' untranslated region (UTR) of mRNA in the 5' to 3' direction till a start codon is encountered, upon which the majority of eIFs sequentially disassemble from the 40S and the resulting 48S initiation complex (48S IC) joins the large ribosomal subunit (60S) to form an elongation-competent 80S ribosome. Kinetoplastids is a group of flagellated unicellular eukaryotic parasites that have a complex life cycle. They spend part of their life cycle in the insect guts before being transmitted to the mammalian host upon biting. Common kinetoplastids include human pathogens such as Trypanosoma cruzi, Trypanosoma brucei and Leishmania spp., etiologic agents of Chagas disease, African sleeping sickness and leishmaniasis, respectively. However, most of the related public health measures are mainly preventative and therapeutic strategies are extremely limited and often highly toxic. Since kinetoplastids have diverged early from other eukaryotes, their mRNA translational machineries developed unique molecular features unseen in other eukaryotic species. For instance, their 40S contains a kinetoplastid-specific ribosomal protein (KSRP) (5) and unusually oversized ribosomal RNA (rRNA) expansion segments (ES S ) (6). Since these unique features may play specific roles in kinetoplastidian mRNA translation, they provide potential specific drug targets.It was proposed that two particularly oversized expansion segments, ES6 S and ES7 S located near the mRNA exit channel on the kinatoplastidian 40S, may contribute to modulating translation initiation in kinetoplastids by interacting with the structural co...

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Section: The Eif5 C-terminal Domain (Ctd) In the Context Of The 43s Picsupporting

confidence: 58%

Structural differences in translation initiation between pathogenic trypanosomatids and their mammalian hosts

Bochler

Querido

Prilepskaja

et al. 2019

Preprint

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“…Finally, there is an unassigned density on top of the β-propeller of eIF3b in contact with eIF2γ, which is more prominently seen in py48S-closed-eIF3 ( Figures 1A, 1D, 2C, 2F, 3A, 3B, 3E and based on its size and proximity to eIF3i or to the C-terminal domain of eIF5 based on the contacts of eIF2γ with the structurally homologous heat domain of eIF2Bε (Kashiwagi et al, 2019;Kenner et al, 2019); although further studies are required to identify it with confidence.…”

Section: Eif3b Bound On the Subunit Interface Of 40smentioning

confidence: 99%

eIF3b and eIF3i relocate together to the ribosomal subunit interface during translation initiation and modulate start codon selection

Llácer

Hussain²,

Gordiyenko

et al. 2018

Preprint

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Running title: eIF3b relocates to the 40S subunit interface and modulates start codon selection 2 ABSTRACT During eukaryotic translational initiation, the 48S ribosomal pre-initiation complex (PIC) scans the 5' untranslated region of mRNA until it encounters a start codon. We present a single particle electron cryomicroscopy (cryo-EM) reconstruction of a yeast 48S PIC in an open scanningcompetent state in which eIF3b is observed bound on the 40S subunit interface. eIF3b is relocated with eIF3i from their solvent-interface locations observed in other PIC structures; however, eIF3i is not in contact with the 40S. Re-processing of micrographs of our previous 48S PIC in a closed state using currently available tools reveal a similar re-location of eIF3b and eIF3i from the solvent to subunit interface. Genetic analysis indicates that high fidelity initiation in vivo depends strongly on eIF3b interactions at the subunit interface that either promote the closed conformation of the PIC on start codon selection or facilitate subsequent relocation back to the solvent side of the 40S subunit.

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“…6A, lane 2, label 48S-uAUG) 15-17 nucleotides away from the uAUG located at 701. A similar uAUG delivery of Met-tRNA i Met can be accomplished by eIF5B which, under stress conditions, has been described to substitute eIF2 for Met-tRNA i Met delivery [51][52][53][54], following then eukaryotic initiation a "bacterial-like" mode of initiation (Fig. 6A, lane 4).…”

Section: Swiveling Of the 40s Head Locks The 5'-utr-ires Inducing A Cmentioning

confidence: 70%

A complex IRES at the 5'-UTR of a viral mRNA assembles a functional 48S complex via an uAUG intermediate

Neupane

Pisareva

Rodríguez

et al. 2020

eLife

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Taking control of the cellular apparatus for protein production is a requirement for virus progression. To ensure this control, diverse strategies of cellular mimicry and/or ribosome hijacking have evolved. The initiation stage of translation is especially targeted as it involves multiple steps and the engagement of numerous initiation factors. The use of structured RNA sequences, called Internal Ribosomal Entry Sites (IRES), in viral RNAs is a widespread strategy for the exploitation of eukaryotic initiation. Using a combination of electron cryo-microscopy (cryo-EM) and reconstituted translation initiation assays with native components, we characterized how a novel IRES at the 5'-UTR of a viral RNA assembles a functional initiation complex via an uAUG intermediate. The IRES features a novel extended, multi-domain architecture, that circles the 40S head. The structures and accompanying functional data illustrate the importance of 5'-UTR regions in translation regulation and underline the relevance of the untapped diversity of viral IRESs.

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eIF2B-catalyzed nucleotide exchange and phosphoregulation by the integrated stress response

Cited by 109 publications

References 43 publications

Structural differences in translation initiation between pathogenic trypanosomatids and their mammalian hosts

Structural differences in translation initiation between pathogenic trypanosomatids and their mammalian hosts

eIF3b and eIF3i relocate together to the ribosomal subunit interface during translation initiation and modulate start codon selection

A complex IRES at the 5'-UTR of a viral mRNA assembles a functional 48S complex via an uAUG intermediate

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