Identification of MAFbx as a myogenin-engaged F-box protein in SCF ubiquitin ligase

FEBS Lett. 2009 Sep 3;583(17):2715-9. doi: 10.1016/j.febslet.2009.07.033. Epub 2009 Jul 22.


Myogenesis is conducted by transcription factors including MyoD and myogenin. Myogenin is known to be polyubiquitinated by SCF (Skp1/Cullin 1/F-box protein) followed by proteasomal degradation, though the participating F-box protein is remaining unidentified. In this study, we found that myogenin in differentiated myoblasts is destabilized by muscle atrophy-inducing dexamethasone and that MAFbx (muscle atrophy F-box protein) is increased in atrophying myotubes. MAFbx overexpression resulted in MG132-sensitive reduction of myogenin. Myogenin had a MAFbx-recognition motif and interacted with MAFbx. MAFbx activated polyubiquitination of myogenin. The results of this study suggest that MAFbx functions as an F-box protein for ubiquitination of myogenin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Dexamethasone / metabolism
  • Glucocorticoids / metabolism
  • Insulin-Like Growth Factor I / metabolism
  • Mice
  • Molecular Sequence Data
  • Muscle Proteins / genetics
  • Muscle Proteins / metabolism*
  • Myoblasts / cytology
  • Myoblasts / physiology
  • Myogenin / genetics
  • Myogenin / metabolism*
  • RNA Interference
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • SKP Cullin F-Box Protein Ligases / genetics
  • SKP Cullin F-Box Protein Ligases / metabolism*


  • Glucocorticoids
  • Muscle Proteins
  • Myog protein, mouse
  • Myogenin
  • Recombinant Fusion Proteins
  • Insulin-Like Growth Factor I
  • Dexamethasone
  • Fbxo32 protein, mouse
  • SKP Cullin F-Box Protein Ligases