Translation of 5' leaders is pervasive in genes resistant to eIF2 repression

Elife. 2015 Jan 26;4:e03971. doi: 10.7554/eLife.03971.

Abstract

Eukaryotic cells rapidly reduce protein synthesis in response to various stress conditions. This can be achieved by the phosphorylation-mediated inactivation of a key translation initiation factor, eukaryotic initiation factor 2 (eIF2). However, the persistent translation of certain mRNAs is required for deployment of an adequate stress response. We carried out ribosome profiling of cultured human cells under conditions of severe stress induced with sodium arsenite. Although this led to a 5.4-fold general translational repression, the protein coding open reading frames (ORFs) of certain individual mRNAs exhibited resistance to the inhibition. Nearly all resistant transcripts possess at least one efficiently translated upstream open reading frame (uORF) that represses translation of the main coding ORF under normal conditions. Site-specific mutagenesis of two identified stress resistant mRNAs (PPP1R15B and IFRD1) demonstrated that a single uORF is sufficient for eIF2-mediated translation control in both cases. Phylogenetic analysis suggests that at least two regulatory uORFs (namely, in SLC35A4 and MIEF1) encode functional protein products.

Keywords: 5′ leader translation; bicistronic mRNA; biochemistry; eukaryotic initiation factor 2 (eIF2); evolutionary biology; genomics; human; integrated stress response (ISR); ribosome profiling; upstream open reading frame (uORF).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arsenites / pharmacology
  • Eukaryotic Initiation Factor-2 / metabolism*
  • Gene Expression Regulation / drug effects
  • Gene Expression Regulation / genetics*
  • HEK293 Cells
  • Humans
  • Immediate-Early Proteins / genetics
  • Immediate-Early Proteins / metabolism
  • Mutagenesis, Site-Directed
  • Open Reading Frames / genetics*
  • Oxidative Stress / drug effects
  • Oxidative Stress / genetics
  • Protein Biosynthesis / drug effects
  • Protein Biosynthesis / genetics*
  • Protein Phosphatase 1 / genetics
  • Protein Phosphatase 1 / metabolism
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Repressor Proteins / metabolism*
  • Ribosomes / drug effects
  • Ribosomes / metabolism
  • Sodium Compounds / pharmacology

Substances

  • Arsenites
  • Eukaryotic Initiation Factor-2
  • IFRD1 protein, human
  • Immediate-Early Proteins
  • RNA, Messenger
  • Repressor Proteins
  • Sodium Compounds
  • sodium arsenite
  • Protein Phosphatase 1