Structural basis of the phosphorylation-independent recognition of cyclin D1 by the SCF FBXO31 ubiquitin ligase

Proc Natl Acad Sci U S A. 2018 Jan 9;115(2):319-324. doi: 10.1073/pnas.1708677115. Epub 2017 Dec 26.

Abstract

Ubiquitin-dependent proteolysis of cyclin D1 is associated with normal and tumor cell proliferation and survival. The SCFFBXO31 (Skp1-Cul1-Rbx1-FBXO31) ubiquitin ligase complex mediates genotoxic stress-induced cyclin D1 degradation. Previous studies have suggested that cyclin D1 levels are maintained at steady state by phosphorylation-dependent nuclear export and subsequent proteolysis in the cytoplasm. Here we present the crystal structures of the Skp1-FBXO31 complex alone and bound to a phosphorylated cyclin D1 C-terminal peptide. FBXO31 possesses a unique substrate-binding domain consisting of two β-barrel motifs, whereas cyclin D1 binds to FBXO31 by tucking its free C-terminal carboxylate tail into an open cavity of the C-terminal FBXO31 β-barrel. Biophysical and functional studies demonstrate that SCFFBXO31 is capable of recruiting and ubiquitinating cyclin D1 in a phosphorylation-independent manner. Our findings provide a conceptual framework for understanding the substrate specificity of the F-box protein FBXO31 and the mechanism of FBXO31-regulated cyclin D1 protein turnover.

Keywords: Skp1–FBXO31–cyclin D1 structure; cell cycle; ubiquitin system.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Crystallography, X-Ray
  • Cyclin D1 / chemistry*
  • Cyclin D1 / genetics
  • Cyclin D1 / metabolism
  • F-Box Proteins / chemistry*
  • F-Box Proteins / genetics
  • F-Box Proteins / metabolism
  • HeLa Cells
  • Humans
  • Models, Molecular
  • Multiprotein Complexes / chemistry*
  • Multiprotein Complexes / metabolism
  • Phosphorylation
  • Protein Binding
  • Protein Domains*
  • Proteolysis
  • Sequence Homology, Amino Acid
  • Substrate Specificity
  • Tumor Suppressor Proteins / chemistry*
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / metabolism
  • Ubiquitination

Substances

  • F-Box Proteins
  • FBXO31 protein, human
  • Multiprotein Complexes
  • Tumor Suppressor Proteins
  • Cyclin D1

Associated data

  • PDB/5VZT
  • PDB/5VZU