Regulation of Pax3 by proteasomal degradation of monoubiquitinated protein in skeletal muscle progenitors.
Pax3 and Pax7 play distinct but overlapping roles in developmental and postnatal myogenesis. The mechanisms involved in the differential regulation of these highly homologous proteins are unknown. We present evidence that Pax3, but not Pax7, is regulated by ubiquitination and proteasomal degradation during adult muscle stem cell activation. Intriguingly, only monoubiquitinated forms of Pax3 could be detected. Mutation of two specific lysine residues in the C-terminal region of Pax3 reduced the extent of its monoubiquitination and susceptibility to proteasomal degradation, whereas introduction of a key lysine into the C-terminal region of Pax7 rendered that protein susceptible to monoubiquitination and proteasomal degradation. Monoubiquitinated Pax3 was shuttled to the intrinsic proteasomal protein S5a by interacting specifically with the ubiquitin-binding protein Rad23B. Functionally, sustained expression of Pax3 proteins inhibited myogenic differentiation, demonstrating that Pax3 degradation is an essential step for the progression of the myogenic program. These results reveal an important mechanism of Pax3 regulation in muscle progenitors and an unrecognized role of protein monoubiquitination in mediating proteasomal degradation.
Department of Neurology and Neurological Sciences, Stanford University School of Medicine, Stanford, CA 94305, USA.
Stéphane C
SC
Boutet
Marie-Hélène
MH
Disatnik
Lauren S
LS
Chan
Kevin
K
Iori
Thomas A
TA
Rando
D000595:Amino Acid Sequence; D000818:Animals; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D024510:Muscle Development; D018482:Muscle, Skeletal / Q000166:cytology* / Q000378:metabolism*; D032448:Myoblasts, Skeletal / Q000166:cytology / Q000378:metabolism*; D000072041:PAX3 Transcription Factor; D051763:PAX7 Transcription Factor / Q000378:metabolism; D051761:Paired Box Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D013816:Thermodynamics; D025801:Ubiquitin / Q000378:metabolism*
D004268:DNA-Binding Proteins; D000072041:PAX3 Transcription Factor; D051763:PAX7 Transcription Factor; D051761:Paired Box Transcription Factors; C499250:Rad23b protein, mouse; D025801:Ubiquitin; C068686:Pax3 protein, mouse; D046988:Proteasome Endopeptidase Complex; D008239:Lysine