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

Myogenesis is conducted by transcription factors including MyoD and myogenin. Myogenin is known to be polyubiquitinated by SCF (Skp1/Cullin1/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. Structured summary: MINT-7222713: Myogenin (uniprotkb: P12979) physically interacts (MI: 0914) with MAFbx ( uniprotkb: Q9CPU7) by anti tag coimmunoprecipitation ( MI: 0007) MINT-7222741: Myogenin ( uniprotkb: P12979) physically interacts (MI: 0914) with MAFbx ( uniprotkb: Q9CPU7) by anti bait coimmunoprecipitation ( MI: 0006) MINT-7222726: Myogenin ( uniprotkb: P12979) and MAFbx (uniprotkb: Q9CPU7) colocalize ( MI: 0403) by fluorescence microscopy (MI: 0416) MINT-7222760: Myogenin ( uniprotkb: P12979) physically interacts ( MI: 0914) with Ubiquitin ( uniprotkb: P62991) by anti bait coimmunoprecipitation ( MI: 0006) (C) 2009 Published by Elsevier B. V. on behalf of the Federation of European Biochemical Societies.