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Mechanism of degrader-targeted protein ubiquitinability

Charlotte Crowe1,2, Mark A Nakasone1,2, Sarah Chandler3

  • 1Centre for Targeted Protein Degradation, School of Life Sciences, University of Dundee, 1 James Lindsay Place, Dundee DD1 5JJ, UK.

Science Advances
|October 11, 2024
PubMed

Insights

Small-molecule degraders harness E3 ligases to eliminate disease proteins. This study reveals how degrader MZ1 positions Brd4 for ubiquitination, identifying key lysine residues crucial for target degradation.

Area of Science:

  • Biochemistry
  • Structural Biology
  • Drug Discovery

Background:

  • Small-molecule degraders are a promising therapeutic strategy targeting disease-driving proteins.
  • Understanding the mechanism of target ubiquitination by degrader-mediated complexes is crucial for drug development.

Purpose of the Study:

  • To elucidate the structural and mechanistic basis of target ubiquitination by small-molecule degraders.
  • To identify key residues and regions involved in the ubiquitination of the target protein Brd4BD2.

Main Methods:

  • Cryo-electron microscopy (cryo-EM) to determine the structure of the VHL-Cullin 2 RING E3 ligase complex with degrader MZ1 and target Brd4BD2.
  • In vitro ubiquitination assays and mass spectrometry to map ubiquitinable lysine residues.
  • Cellular degradation assays and ubiquitinomics to validate key lysine residues in vivo.

Main Results:

  • Cryo-EM structures revealed the precise positioning of Brd4BD2 for ubiquitination by UBE2R1-ubiquitin.
  • A specific "ubiquitination zone" on Brd4BD2, including Lys456, Lys368, and Lys445, was identified as critical for degradation.
  • The study highlights the catalytic efficiency of the degrader and the flexibility of the E3 ligase complex.

Conclusions:

  • A mechanistic model for the ubiquitination of degrader-recruited targets was proposed.
  • These findings provide a blueprint for the rational design of more effective small-molecule degraders.
  • The study advances our understanding of targeted protein degradation mechanisms.

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