FBW2 targets GCMa to the ubiquitin-proteasome degradation system.
The GCM proteins GCMa/1 and GCMb/2 are novel zinc-containing transcription factors critical for glial cell differentiation in fly and for placental as well as parathyroid gland development in mouse. Previous pulse-chase experiments have demonstrated differential protein stabilities of GCM proteins with half-lives from approximately 30 min to 2 h (Tuerk, E. E., Schreiber, J., and Wegner, M. (2000) J. Biol. Chem. 275, 4774-4782). However, little is known about the machinery that controls GCM protein degradation. Here, we report the identification of an SCF complex as the GCM ubiquitin-protein isopeptide ligase (E3) that regulates human GCMa (hGCMa) degradation. We found that SKP1 and CUL1, two key components of the SCF complex, associate with hGCMa in vivo. We further identify the human F-box protein FBW2 (hFBW2) as the substrate recognition subunit in the SCF E3 complex for hGCMa. We show that hFBW2 interacts with hGCMa in a phosphorylation-dependent manner and promotes hGCMa ubiquitination. Supporting a critical role for hFBW2 in hGCMa degradation, knockdown of hFBW2 expression by RNA interference leads to a reduction in hGCMa ubiquitination and a concomitant increase in hGCMa protein stability. Our study identifies the SCF(hFBW2) E3 complex as the key machinery that targets hGCMa to the ubiquitin-proteasome degradation system.
Yang
Chih-Sheng
CS
Graduate Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan.
Yu
Chenchou
C
Chuang
Hsiao-Ching
HC
Chang
Ching-Wen
CW
Chang
Geen-Dong
GD
Yao
Tso-Pang
TP
Chen
Hungwen
H
D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D002454:Cell Differentiation; D002460:Cell Line; D044842:Cullin Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D044783:F-Box Proteins / Q000378:metabolism / Q000502:physiology*; D020868:Gene Silencing; D006801:Humans; D047468:Immunoprecipitation; D009457:Neuroglia / Q000166:cytology; D009479:Neuropeptides / Q000378:metabolism*; D010710:Phosphates / Q000737:chemistry; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D044786:S-Phase Kinase-Associated Proteins / Q000378:metabolism; D019089:Stem Cell Factor / Q000378:metabolism; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection; D025801:Ubiquitin / Q000378:metabolism*
D018797:Cell Cycle Proteins; C100318:Cullin 1; D044842:Cullin Proteins; D044783:F-Box Proteins; C499832:FBXW2 protein, human; C471536:Fbxw2 protein, mouse; D009479:Neuropeptides; D010710:Phosphates; D044786:S-Phase Kinase-Associated Proteins; D019089:Stem Cell Factor; D015534:Trans-Activators; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex