title: Degradation of MyoD mediated by the SCF (MAFbx) ubiquitin ligase.
abstract: 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.
authors.affiliation: 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.
authors.forename: Lionel A
authors.initials: LA
authors.lastname: Tintignac
authors.forename: Julie
authors.initials: J
authors.lastname: Lagirand
authors.forename: Sabrina
authors.initials: S
authors.lastname: Batonnet
authors.forename: Valentina
authors.initials: V
authors.lastname: Sirri
authors.forename: Marie Pierre
authors.initials: MP
authors.lastname: Leibovitch
authors.forename: Serge A
authors.initials: SA
authors.lastname: Leibovitch
mesh_terms: 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
chemical_list: D017570:MyoD Protein; D011994:Recombinant Proteins; D019089:Stem Cell Factor; D025801:Ubiquitin; D004247:DNA; D044843:SKP Cullin F-Box Protein Ligases; D008239:Lysine