Phosphorylation-dependent ubiquitination of cyclin D1 by the SCF(FBX4-alphaB crystallin) complex

Mol Cell. 2006 Nov 3;24(3):355-66. doi: 10.1016/j.molcel.2006.09.007.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Catalysis
  • Cyclin D1 / metabolism*
  • Cytoplasm / metabolism
  • F-Box Proteins / chemistry
  • F-Box Proteins / genetics
  • F-Box Proteins / metabolism*
  • G1 Phase / physiology
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Mice
  • NIH 3T3 Cells
  • Neoplasms / genetics
  • Phosphorylation
  • Phosphothreonine / metabolism
  • Protein Binding
  • Protein Transport
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • SKP Cullin F-Box Protein Ligases / metabolism*
  • Thermodynamics
  • Ubiquitin / metabolism*
  • alpha-Crystallin B Chain / genetics
  • alpha-Crystallin B Chain / metabolism*

Substances

  • F-Box Proteins
  • FBXO4 protein, human
  • Fbx4 protein, mouse
  • RNA, Messenger
  • Ubiquitin
  • alpha-Crystallin B Chain
  • Phosphothreonine
  • Cyclin D1
  • SKP Cullin F-Box Protein Ligases