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Phosphorylation-dependent BRD4 dimerization and implications for therapeutic inhibition of BET family proteins

Francesca Malvezzi1,2, Christopher J Stubbs1, Thomas A Jowitt3

  • 1Structure, Biophysics and Fragment-Based Lead Generation, Discovery Sciences, BioPharmaceuticals R&D, AstraZeneca, Cambridge, UK.

Communications Biology
|November 10, 2021
PubMed

Insights

Phosphorylation by CK2 regulates bromodomain-containing protein 4 (BRD4) dimerization, revealing a new target for cancer drug development. This structural insight into BRD4 function is key for improving oncology therapeutics.

Area of Science:

  • Epigenetics
  • Structural Biology
  • Cancer Therapeutics

Background:

  • Bromodomain-containing protein 4 (BRD4) is a key epigenetic regulator and oncology drug target.
  • BRD4 function is modulated by phosphorylation, impacting gene transcription and drug resistance in cancers like triple-negative breast cancer.

Purpose of the Study:

  • To perform the first biophysical analysis of BRD4 phospho-regulation.
  • To elucidate the structural mechanisms underlying BRD4 function and its modulation by phosphorylation.

Main Methods:

  • Integrative structural biology techniques.
  • Biophysical analysis of BRD4 protein.
  • In vitro and in cell-based assays.

Main Results:

  • Phosphorylation by casein kinase II (CK2) modulates human BRD4 dimerization.
  • Identified a phosphorylation-dependent dimerization domain (PDD) comprising a coiled-coil motif and the Basic-residue enriched Interaction Domain (BID).
  • Bivalent inhibitors induce conformational changes in BRD4 dimers in vitro and in cancer cells.

Conclusions:

  • A model for BRD4 activation based on phosphorylation-dependent dimerization is proposed.
  • Findings are critical for understanding BRD4's protein-protein interaction network.
  • Provides a basis for developing more specific BRD4-targeted cancer therapeutics.

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