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.
Mesh Terms:
Animals, Catalysis, Cyclin D1, Cytoplasm, F-Box Proteins, G1 Phase, Gene Expression Regulation, Neoplastic, Humans, Mice, NIH 3T3 Cells, Neoplasms, Phosphorylation, Phosphothreonine, Protein Binding, Protein Transport, RNA, Messenger, SKP Cullin F-Box Protein Ligases, Thermodynamics, Ubiquitin, alpha-Crystallin B Chain
Mol. Cell
Date: Nov. 03, 2006
Download Curated Data For This Publication
99395
Switch View:
  • Interactions 17