Molecular architecture of 40S initiation complexes on the Hepatitis C virus IRES: from ribosomal attachment to eIF5B-mediated reorientation of initiator tRNA

Brown, Z. P.; Abaeva, I. S.; De, S.; Hellen, C. U. T.; Pestova, T. V.; Frank, J.

doi:10.1101/2021.12.10.472117

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bioRxiv · 10.1101/2021.12.10.472117

Molecular architecture of 40S initiation complexes on the Hepatitis C virus IRES: from ribosomal attachment to eIF5B-mediated reorientation of initiator tRNA

Brown, Z. P.·Abaeva, I. S.·De, S.·Hellen, C. U. T.·Pestova, T. V.·Frank, J.

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Abstract

Hepatitis C virus mRNA contains an internal ribosome entry site (IRES) that mediates end-independent translation initiation, requiring a subset of eukaryotic initiation factors (eIFs). Direct binding of the IRES to the 40S subunit places the initiation codon into the P site, where it base-pairs with eIF2-bound Met-tRNAiMet forming a 48S initiation complex. Then, eIF5 and eIF5B mediate subunit joining. Initiation can also proceed without eIF2, in which case Met-tRNAiMet is recruited directly by eIF5B. Here, we present cryo-EM structures of IRES initiation complexes at resolutions up to 3.5 [A] that cover all major stages from initial ribosomal association, through eIF2-containing 48S initiation complexes, to eIF5B-containing complexes immediately prior to subunit joining. These structures provide insights into the dynamic network of 40S/IRES contacts, highlight the role for IRES domain II, and reveal conformational changes that occur during the transition from eIF2- to eIF5B-containing 48S complexes that prepare them for subunit joining.

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Brown, Z. P., Abaeva, I. S., De, S., Hellen, C. U. T., Pestova, T. V., Frank, J.. 2021-12-11. Molecular architecture of 40S initiation complexes on the Hepatitis C virus IRES: from ribosomal attachment to eIF5B-mediated reorientation of initiator tRNA. https://doi.org/10.1101/2021.12.10.472117

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