Degradation of MyoD mediated by the SCF (MAFbx) ubiquitin ligase.
MyoD controls myoblast identity and differentiation and is required for myogenic stem cell function in adult skeletal muscle. MyoD is degraded by the ubiquitin-proteasome pathway mediated by different E3 ubiquitin ligases not identified as yet. Here we report that MyoD interacts with Atrogin-1/MAFbx (MAFbx), a striated muscle-specific E3 ubiquitin ligase dramatically up-regulated in atrophying muscle. A core LXXLL motif sequence in MyoD is necessary for binding to MAFbx. MAFbx associates with MyoD through an inverted LXXLL motif located in a series of helical leucine-charged residue-rich domains. Mutation in the LXXLL core motif represses ubiquitination and degradation of MyoD induced by MAFbx. Overexpression of MAFbx suppresses MyoD-induced differentiation and inhibits myotube formation. Finally the purified recombinant SCF(MAFbx) complex (SCF, Skp1, Cdc53/Cullin 1, F-box protein) mediated MyoD ubiquitination in vitro in a lysine-dependent pathway. Mutation of the lysine 133 in MyoD prevented its ubiquitination by the recombinant SCF(MAFbx) complex. These observations thus demonstrated that MAFbx functions in ubiquitinating MyoD via a sequence found in transcriptional coactivators. These transcriptional coactivators mediate the binding to liganded nuclear receptors. We also identified a novel protein-protein interaction module not yet identified in F-box proteins. MAFbx may play an important role in the course of muscle differentiation by determining the abundance of MyoD.
Tintignac
Lionel A
LA
Laboratoire de Génomique Fonctionnelle et Myogénèse, UMR866 Différenciation Cellulaire et Croissance, INRA UM II, Campus INRA/ENSA, 2 Place Pierre Viala, 34060, Montpellier, Cedex 1, France.
Lagirand
Julie
J
Batonnet
Sabrina
S
Sirri
Valentina
V
Leibovitch
Marie Pierre
MP
Leibovitch
Serge A
SA
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D008239:Lysine / Q000737:chemistry; D051379:Mice; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D017570:MyoD Protein / Q000737:chemistry* / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D019089:Stem Cell Factor / Q000378:metabolism; D013997:Time Factors; D014158:Transcription, Genetic; D014162:Transfection; D020798:Two-Hybrid System Techniques; D025801:Ubiquitin / Q000378:metabolism
D017570:MyoD Protein; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D025801:Ubiquitin; D004247:DNA; D044843:SKP Cullin F-Box Protein Ligases; D008239:Lysine