Phosphorylation-dependent ubiquitination of cyclin D1 by the SCF(FBX4-alphaB crystallin) complex.
Growth factor-dependent accumulation of the cyclin D1 proto-oncogene is balanced by its rapid phosphorylation-dependent proteolysis. Degradation is triggered by threonine 286 phosphorylation, which promotes its ubiquitination by an unknown E3 ligase. We demonstrate that Thr286-phosphorylated cyclin D1 is recognized by a Skp1-Cul1-F box (SCF) ubiquitin ligase where FBX4 and alphaB crystallin govern substrate specificity. Overexpression of FBX4 and alphaB crystallin triggered cyclin D1 ubiquitination and increased cyclin D1 turnover. Impairment of SCF(FBX4-alphaB crystallin) function attenuated cyclin D1 ubiquitination, promoting cyclin D1 overexpression and accelerated cell-cycle progression. Purified SCF(FBX4-alphaB crystallin) catalyzed polyubiquitination of cyclin D1 in vitro. Consistent with a putative role for a cyclin D1 E3 ligase in tumorigenesis, FBX4 and alphaB crystallin expression was reduced in tumor-derived cell lines and a subset of primary human cancers that overexpress cyclin D1. We conclude that SCF(FBX4-alphaB crystallin) is an E3 ubiquitin ligase that promotes ubiquitin-dependent degradation of Thr286-phosphorylated cyclin D1.
Lin
Douglas I
DI
The Leonard and Madlyn Abramson Family Cancer Research Institute and Cancer Center, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Barbash
Olena
O
Kumar
K G Suresh
KG
Weber
Jason D
JD
Harper
J Wade
JW
Klein-Szanto
Andres J P
AJ
Rustgi
Anil
A
Fuchs
Serge Y
SY
Diehl
J Alan
JA
D000818:Animals; D002384:Catalysis; D019938:Cyclin D1 / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D044783:F-Box Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016193:G1 Phase / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000235:genetics; D010766:Phosphorylation; D010769:Phosphothreonine / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D044843:SKP Cullin F-Box Protein Ligases / Q000378:metabolism*; D013816:Thermodynamics; D025801:Ubiquitin / Q000378:metabolism*; D038203:alpha-Crystallin B Chain / Q000235:genetics / Q000378:metabolism*
D044783:F-Box Proteins; C508146:FBXO4 protein, human; C515213:Fbx4 protein, mouse; C000715470:MAS1 protein, human; D000090063:Proto-Oncogene Mas; D012333:RNA, Messenger; D025801:Ubiquitin; D038203:alpha-Crystallin B Chain; D010769:Phosphothreonine; D019938:Cyclin D1; D044843:SKP Cullin F-Box Protein Ligases