A structural inventory of native ribosomal ABCE1-43S pre-initiation complexes

EMBO J. 2021 Jan 4;40(1):e105179. doi: 10.15252/embj.2020105179. Epub 2020 Dec 8.

Abstract

In eukaryotic translation, termination and ribosome recycling phases are linked to subsequent initiation of a new round of translation by persistence of several factors at ribosomal sub-complexes. These comprise/include the large eIF3 complex, eIF3j (Hcr1 in yeast) and the ATP-binding cassette protein ABCE1 (Rli1 in yeast). The ATPase is mainly active as a recycling factor, but it can remain bound to the dissociated 40S subunit until formation of the next 43S pre-initiation complexes. However, its functional role and native architectural context remains largely enigmatic. Here, we present an architectural inventory of native yeast and human ABCE1-containing pre-initiation complexes by cryo-EM. We found that ABCE1 was mostly associated with early 43S, but also with later 48S phases of initiation. It adopted a novel hybrid conformation of its nucleotide-binding domains, while interacting with the N-terminus of eIF3j. Further, eIF3j occupied the mRNA entry channel via its ultimate C-terminus providing a structural explanation for its antagonistic role with respect to mRNA binding. Overall, the native human samples provide a near-complete molecular picture of the architecture and sophisticated interaction network of the 43S-bound eIF3 complex and the eIF2 ternary complex containing the initiator tRNA.

Keywords: ABCE1; cryo-EM; eIF3; ribosome recycling; translation initiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP-Binding Cassette Transporters / metabolism*
  • Cell Line
  • DNA-Binding Proteins / metabolism
  • Eukaryotic Initiation Factor-2 / metabolism
  • HEK293 Cells
  • Humans
  • Protein Binding / physiology
  • Protein Biosynthesis / physiology
  • RNA, Messenger / metabolism
  • RNA, Transfer / metabolism
  • Ribosome Subunits, Small, Eukaryotic / metabolism*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / metabolism

Substances

  • ABCE1 protein, human
  • ATP-Binding Cassette Transporters
  • DNA-Binding Proteins
  • Eukaryotic Initiation Factor-2
  • RNA, Messenger
  • Saccharomyces cerevisiae Proteins
  • RNA, Transfer

Associated data

  • PDB/6ZCE
  • PDB/6ZU9
  • PDB/7A1G
  • PDB/6ZVJ
  • PDB/7A09