Non-cooperative 4E-BP2 folding with exchange between eIF4E-binding and binding-incompatible states tunes cap-dependent translation inhibition

Nat Commun. 2020 Jun 19;11(1):3146. doi: 10.1038/s41467-020-16783-8.

Abstract

Phosphorylation of intrinsically disordered eIF4E binding proteins (4E-BPs) regulates cap-dependent translation by weakening their ability to compete with eIF4G for eIF4E binding within the translation initiation complex. We previously showed that phosphorylation of T37 and T46 in 4E-BP2 induces folding of a four-stranded beta-fold domain, partially sequestering the canonical eIF4E-binding helix. The C-terminal intrinsically disordered region (C-IDR), remaining disordered after phosphorylation, contains the secondary eIF4E-binding site and three other phospho-sites, whose mechanisms in inhibiting binding are not understood. Here we report that the domain is non-cooperatively folded, with exchange between beta strands and helical conformations. C-IDR phosphorylation shifts the conformational equilibrium, controlling access to eIF4E binding sites. The hairpin turns formed by pT37/pT46 are remarkably stable and function as transplantable units for phospho-regulation of stability. These results demonstrate how non-cooperative folding and conformational exchange leads to graded inhibition of 4E-BP2:eIF4E binding, shifting 4E-BP2 into an eIF4E binding-incompatible conformation and regulating translation initiation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Computational Biology
  • Eukaryotic Initiation Factor-4E / genetics
  • Eukaryotic Initiation Factor-4E / metabolism*
  • Intrinsically Disordered Proteins / genetics
  • Intrinsically Disordered Proteins / metabolism*
  • Mutagenesis, Site-Directed
  • Nuclear Magnetic Resonance, Biomolecular
  • Phosphorylation / physiology
  • Protein Binding / genetics
  • Protein Biosynthesis / physiology*
  • Protein Conformation, alpha-Helical / genetics
  • Protein Conformation, beta-Strand / genetics
  • Protein Folding
  • Protein Processing, Post-Translational / physiology
  • RNA Caps / metabolism*

Substances

  • Eukaryotic Initiation Factor-4E
  • Intrinsically Disordered Proteins
  • RNA Caps