Structural Changes Enable Start Codon Recognition by the Eukaryotic Translation Initiation Complex

Hussain, Tanweer; Llácer, J.L.; Fernandez, I.S.; Munoz, Antonio; Martín-Marcos, Pilar; Savva, Christos G.; Lorsch, Jon R.; Hinnebusch, Alan G.; Ramakrishnan, V.

doi:10.1016/j.cell.2014.10.001

Cited by 179 publications

(420 citation statements)

References 57 publications

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“…It releases phosphate as a consequence of the stable binding of the tRNAi anticodon to the start-codon. As observed for the scaffolding factors and 40S, eIF2 also makes minimal contact with the 40S, maintaining approximately 34 Å separation from the body of the subunit and passing above eIF1 and eIF1A [9,14,15,20]. The only significant contact is made with the head within the E-site adjacent to the P-site occupied by the tRNA itself [20].…”

Section: Start-codon Selection: To Stay or To Gomentioning

confidence: 91%

“…As observed for the scaffolding factors and 40S, eIF2 also makes minimal contact with the 40S, maintaining approximately 34 Å separation from the body of the subunit and passing above eIF1 and eIF1A [9,14,15,20]. The only significant contact is made with the head within the E-site adjacent to the P-site occupied by the tRNA itself [20]. This ensures that the ternary complex moves with the flexible 40S head in relation to the body of the subunit, while the contacts made with eIF1 and eIF1A will vary with head movement [9].…”

Section: Start-codon Selection: To Stay or To Gomentioning

confidence: 99%

“…This ensures that the ternary complex moves with the flexible 40S head in relation to the body of the subunit, while the contacts made with eIF1 and eIF1A will vary with head movement [9]. The eIF2 GAP eIF5 was resolved only extremely weakly as a cloud of density abutting eIF2 [20]. This is not unexpected since eIF5 represents the flexible 'handle' by which eIF3 may recruit the ternary complex, eIF3 having substantially greater affinity for eIF5 than eIF2, ensuring that the GTPase is active and primed due to its GAP activity.…”

Section: Start-codon Selection: To Stay or To Gomentioning

confidence: 99%

“…Binding by eIF1A keeps the rRNA bases within the decoding site in a flippedout conformation, facilitating mRNA scanning by minimizing the interaction between the mRNA and rRNA in the mRNA channel [18], and eIF1 protrudes with a conserved loop into the mRNA channel, ready to sense cognate codon-anticodon base pairing [17,19]. The ternary complex, which consists of charged Met-tRNAi in a selective complex in which the acceptor stem is cradled by eIF2, is incorporated directly into the P-site on its recruitment by the multifactor complex [9,14,15,20]. eIF2 is a GTPase, which binds in a state in which GTP has already been hydrolysed.…”

Section: Start-codon Selection: To Stay or To Gomentioning

confidence: 99%

“…Our structural understanding of this initiation intermediate is a montage of initial high- [17,18] and intermediate-resolution [19] crystal structures of small protein factors and tRNAi, fleshed out to completeness through cryo-EM structures spanning a wide range of resolutions [8,9,[13][14][15]19,20]. While eIF1, eIF1A, tRNAi and parts of eIF2a are resolved to a molecular level, several other factors (eIF5, parts of eIF3 on the subunit interface) are of such low resolution that their identity must be considered tentative rather than final ( figure 3).…”

Section: Start-codon Selection: To Stay or To Gomentioning

confidence: 99%

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Eukaryotic aspects of translation initiation brought into focus

Aylett

Ban

2017

Phil. Trans. R. Soc. B

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One contribution of 11 to a theme issue 'Perspectives on the ribosome'. In all organisms, mRNA-directed protein synthesis is catalysed by ribosomes. Although the basic aspects of translation are preserved in all kingdoms of life, important differences are found in the process of translation initiation, which is rate-limiting and the most important step for translation regulation. While great strides had been taken towards a complete structural understanding of the initiation of translation in eubacteria, our understanding of the eukaryotic process, which includes numerous eukaryotic-specific initiation factors, was until recently limited owing to a lack of structural information. In this review, we discuss recent results in the field that provide an increasingly complete molecular description of the eukaryotic initiation process. The structural snapshots obtained using a range of methods now provide insights into the architecture of the initiation complex, start-codon recognition by the initiator tRNA and the process of subunit joining. Future advances will require both higher-resolution insights into previously characterized complexes and mapping of initiation factors that control translation on an additional level by interacting only peripherally or transiently with ribosomal subunits.This article is part of the themed issue 'Perspectives on the ribosome'. Eubacterial translation initiationAt its most basic level, the process of translation initiation encompasses only a few key steps. The mRNA molecule undergoing translation must bind to the mRNA channel on the small ribosomal subunit such that the start-codon is positioned into the P-( peptidyl) decoding site. A charged initiator tRNA, in prokaryotes generally (formyl) methionyl-tRNAi, must then be bound at the aforementioned start-codon, decoding the first triplet of the encoded protein establishing the frame in which the eventual addition of the following tRNA adaptor molecules will be incorporated. Finally, the large ribosomal subunit joins the small subunit to form ribosomal complex with initiator tRNA in the P site of the ribosome primed for the elongation stage of protein synthesis during which protein is synthesized based on the message encoded in the RNA. Owing to the large investment of energy involved in translation, this entire process is tightly regulated at the stage of initiation, reducing the wasteful expenditure of resources. In eubacteria, translation initiation is facilitated by two universally conserved factors, IFs (initiation factors) 1 (note that this homologue of eubacterial IF1 in eukaryotes is named eIF1A: eIF1 is a separate factor) and 2, and a region of rRNA dubbed the anti-Shine-Dalgarno sequence [1,2]. The position of the first codon within the decoding site is established by base pairing between the Shine-Dalgarno sequence, located upstream of the first codon within the mRNA, and its complement within the ribosomal rRNA [2]. The separation between the two mRNA elements then defines the start site for translation [2]. Recruitment ...

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Section: Start-codon Selection: To Stay or To Gomentioning

confidence: 91%

Section: Start-codon Selection: To Stay or To Gomentioning

confidence: 99%

Section: Start-codon Selection: To Stay or To Gomentioning

confidence: 99%

Section: Start-codon Selection: To Stay or To Gomentioning

confidence: 99%

Section: Start-codon Selection: To Stay or To Gomentioning

confidence: 99%

See 3 more Smart Citations

Eukaryotic aspects of translation initiation brought into focus

Aylett

Ban

2017

Phil. Trans. R. Soc. B

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Archaeal and eukaryal translation initiation factor 1 differ in their RNA interacting loops

Gogoi

Kanaujia

2018

FEBS Letters

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The archaeal translation initiation factor 1 (aIF1) is reported to be functionally homologous to the eukaryotic translation initiation factor 1 (eIF1). However, lack of a structural comparison between aIF1 and eIF1 has limited our understanding of the structural (dis)similarities. Herein, we have determined the three-dimensional crystal structure of an open reading frame PH1771.1 encoding aIF1 in Pyrococcus horikoshii OT3. Results reveal that although aIF1 has low sequence similarity with eIF1, high structural homology exists between the two proteins. Nonetheless, notable critical differences between aIF1 and eIF1 could still be perceived at the β -β basic loop, the acidic loop and the solvent-exposed surface. These differences might lead to a slightly divergent mode of action of aIF1 during archaeal translation initiation.

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Ribosomal mutation in helix 32 of 18S rRNA alters fidelity of eukaryotic translation start site selection

Ram

Dutta

et al. 2019

FEBS Letters

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The 40S ribosome plays a critical role in start codon selection. To gain insights into the role of its 18S rRNA in start codon selection, a suppressor screen was performed that suppressed the preferential UUG start codon recognition (Suppressor of initiation codon: Sui− phenotype) associated with the eIF5G31R mutant. The C1209U mutation in helix h32 of 18S rRNA was found to suppress the Sui− and Gcn− (failure to derepress GCN4 expression) phenotype of the eIF5G31R mutant. The C1209U mutation suppressed Sui− and Gcd− (constitutive derepression of GCN4 expression) phenotype of eIF2βS264Y, eIF1K60E, and eIF1A‐ΔC mutation. We propose that the C1209U mutation in 40S ribosomal may perturb the premature head rotation in ‘Closed/PIN’ state and enhance the stringency of translation start site selection.

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Structural Changes Enable Start Codon Recognition by the Eukaryotic Translation Initiation Complex

Cited by 179 publications

References 57 publications

Eukaryotic aspects of translation initiation brought into focus

Eukaryotic aspects of translation initiation brought into focus

Archaeal and eukaryal translation initiation factor 1 differ in their RNA interacting loops

Ribosomal mutation in helix 32 of 18S rRNA alters fidelity of eukaryotic translation start site selection

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