Structure of the mammalian ribosomal 43S preinitiation complex bound to the scanning factor DHX29

By Y. Hashem, Amédée des Georges, Vidya Dhote, R. Langlois, H. Liao, R. Grassucci, C. Hellen, T. Pestova, Joachim Frank. 2013

219 citations recorded by the source corpus.

Eukaryotic translation initiation begins with assembly of a 43S preinitiation complex. First, Met-tRNAiMet, eukaryotic initiation factor 2 (eIF2) and GTP form a ternary complex (TC). The TC, eIF3, eIF1 and eIF1A cooperatively bind to the 40S subunit yielding the 43S preinitiation complex, which is ready to attach to mRNA and start scanning to the initiation codon. Scanning on structured mRNAs additionally requires DHX29, a DExH-box protein that also binds directly to the 40S subunit. Here, we present a cryo-electron microscopy structure of the mammalian DHX29-bound 43S complex at 11.6Å resolution. It reveals that eIF2 interacts with the 40S subunit via its α-subunit and supports Met-tRNAiMet in a novel P/I orientation (eP/I). The structural core of eIF3 resides on the back of the 40S subunit establishing two principal points of contact, whereas DHX29 binds around helix 16. The structure provides insights into eukaryote-specific aspects of translation, including the mechanism of action of DHX29.

Subfields: Molecular Biology

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In Molecular Biology

1. A. Hinnebusch
2. I. S. Fernández
3. M. Sokabe
4. C. Fraser
5. Y. Hashem
6. W. Merrick
7. G. Pavitt
8. Joachim Frank

Citations in the corpus

• A structural model of the active ribosome-bound membrane protein insertase YidC (2014, background): “, 2014b), ribosomal complexes involved in physiological processes show a higher degree of structural heterogeneity (Frauenfeld et al., 2011; Hashem et al., 2013; Leidig et al., 2013; Bischoff et al., 2014b; Gogala et al., 2014).”
• The scanning mechanism of eukaryotic translation initiation. (2014, methodology): “Considering that the cryo-EM structure of the 43S/Dhx29 PIC, which presumably depicts the POUT state, also reveals that Met-tRNAi (in the TC) tilts toward the E site (46), the movement of Met-tRNAi between the POUT and PIN states may be subtle.”
• Protein Synthesis Initiation in Eukaryotic Cells. (2018, background): “…and monitor important events occurring at both the mRNA entry channel/A site as well as the exit channel/E site and factor binding to the intersubunit interface (Hashem et al. 2013b; Erzberger et al. 2014; Aylett et al. 2015; des Georges et al. 2015; Llacer et al. 2015; Simonetti et al. 2016).”
• Structural Insights into the Mechanism of Scanning and Start Codon Recognition in Eukaryotic Translation Initiation. (2017, methodology): “eIF2b Exhibits Contacts with eIF1, eIF1A, and the tRNAi ASL Restricted to py48S-Open In previous py48S [20] and pm43S [24] structures, only the N-terminal helix of eIF2b was visualized, where it attaches to eIF2g.”
• The Jigsaw Puzzle of mRNA Translation Initiation in Eukaryotes: A Decade of Structures Unraveling the Mechanics of the Process (2018, methodology): “As the largest and most complex initiation factor, eIF3 is involved in virtually all steps of initiation, including the attachment of 43S PICs to mRNA (through the interaction with eIF4G), the ribosomal recruitment of the TC, and ensuring the fidelity of the scanning process for the correct start co”
• Structural Changes Enable Start Codon Recognition by the Eukaryotic Translation Initiation Complex (2014, methodology): “Instead, it is similar to the conformation of tRNAi (eP/ I state) observed in the pm43S (Hashem et al., 2013) (Figures 2C and S5A).”
• Toward a Kinetic Understanding of Eukaryotic Translation. (2018, background): “However, other initiation components may contribute to stabilizing this conformation because structures of 40S subunit complexes that include eIF1 and eIF1A adopt a closed conformation (Hashem et al. 2013; Lomakin and Steitz 2013; Weisser et al. 2013).”
• One number does not fit all: mapping local variations in resolution in cryo-EM reconstructions (2013, methodology): “In another study on the mammalian ribosomal 43S preinitiation complex (Hashem et al., 2013a,b), localized resolution assessment was used to identify components with partial occupancy.”