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Structural Basis for Substrate Selectivity of the E3 Ligase COP1.

Sacha Uljon1, Xiang Xu2, Izabela Durzynska3

  • 1Department of Cancer Biology, Dana Farber Cancer Institute, Boston, MA 02215, USA; Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA; Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA.

Structure (London, England : 1993)
|April 5, 2016
PubMed
Summary

Constitutive photomorphogenic 1 (COP1) proteins are E3 ubiquitin ligases. Structural studies reveal how COP1 recognizes Trib1 peptide motifs, uncovering key interactions for targeting C/EBPα for degradation.

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Area of Science:

  • Molecular Biology
  • Structural Biology
  • Biochemistry

Background:

  • COP1 proteins function as E3 ubiquitin ligases in plants and mammals.
  • COP1's substrate-binding region is within its WD40-repeat domain.
  • Trib proteins act as adaptors for C/EBPα degradation via COP1.

Purpose of the Study:

  • To determine the structures of human and Arabidopsis thaliana COP1 WD40 domains.
  • To elucidate the structural basis of Trib1 binding to COP1.
  • To understand the mechanism of C/EBPα degradation targeting.

Main Methods:

  • X-ray crystallography
  • Structural analysis of isolated and complexed COP1 WD40 domains
  • Peptide binding studies

Main Results:

  • The human and Arabidopsis COP1 WD40 domains are seven-bladed β-propellers.
  • Trib1 peptide binds to a conserved surface on the top face of the COP1 WD40 domain in an extended conformation.
  • Identified key interactions for COP1-motif recognition.

Conclusions:

  • The study reveals the structural basis for peptide motif recognition by COP1.
  • The findings suggest a general mechanism for how COP1 recognizes its substrates.
  • The results provide insights into how Trib1 overcomes autoinhibition to target C/EBPα.