AU-rich-element-mediated upregulation of translation by FXR1 and Argonaute 2

Cell. 2007 Mar 23;128(6):1105-18. doi: 10.1016/j.cell.2007.01.038.


AU-rich elements (AREs), present in mRNA 3'-UTRs, are potent posttranscriptional regulatory signals that can rapidly effect changes in mRNA stability and translation, thereby dramatically altering gene expression with clinical and developmental consequences. In human cell lines, the TNFalpha ARE enhances translation relative to mRNA levels upon serum starvation, which induces cell-cycle arrest. An in vivo crosslinking-coupled affinity purification method was developed to isolate ARE-associated complexes from activated versus basal translation conditions. We surprisingly found two microRNP-related proteins, fragile-X-mental-retardation-related protein 1 (FXR1) and Argonaute 2 (AGO2), that associate with the ARE exclusively during translation activation. Through tethering and shRNA-knockdown experiments, we provide direct evidence for the translation activation function of both FXR1 and AGO2 and demonstrate their interdependence for upregulation. This novel cell-growth-dependent translation activation role for FXR1 and AGO2 allows new insights into ARE-mediated signaling and connects two important posttranscriptional regulatory systems in an unexpected way.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions / genetics*
  • 3' Untranslated Regions / metabolism
  • Argonaute Proteins
  • Cell Cycle
  • Cell Line
  • Chromatography, Affinity
  • Culture Media, Serum-Free
  • Eukaryotic Initiation Factor-2
  • Genes, Reporter
  • Humans
  • Luciferases, Firefly / genetics
  • Monocytes / cytology
  • Monocytes / metabolism
  • Peptide Initiation Factors / metabolism*
  • Polyribosomes / metabolism
  • Protein Biosynthesis*
  • RNA-Binding Proteins / metabolism*
  • Regulatory Sequences, Ribonucleic Acid
  • Ribonucleoproteins / metabolism
  • Serum / metabolism
  • Tumor Necrosis Factor-alpha / genetics*
  • Up-Regulation*


  • 3' Untranslated Regions
  • AGO2 protein, human
  • Argonaute Proteins
  • Culture Media, Serum-Free
  • Eukaryotic Initiation Factor-2
  • FXR1 protein, human
  • Peptide Initiation Factors
  • RNA-Binding Proteins
  • Regulatory Sequences, Ribonucleic Acid
  • Ribonucleoproteins
  • TNF protein, human
  • Tumor Necrosis Factor-alpha
  • Luciferases, Firefly