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Comparative Strategies for Ubiquitination Detection in Mammalian Cell Lysates Using SMAD2/SMURF2 as a Model
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Comparative Strategies for Ubiquitination Detection in Mammalian Cell Lysates Using SMAD2/SMURF2 as a Model

Published on: April 17, 2026

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Inducible STAT3 NH2 terminal mono-ubiquitination promotes BRD4 complex formation to regulate apoptosis

Sutapa Ray1, Yingxin Zhao2, Mohammad Jamaluddin3

  • 1Sealy Center for Molecular Medicine, University of Texas Medical Branch, Galveston, TX 77555, United States; Department of Internal Medicine, University of Texas Medical Branch, Galveston, TX 77555, United States.

Cellular Signalling
|March 25, 2014
PubMed

Insights

Signal Transducers and Activator of Transcription-3 (STAT3) mono-ubiquitination enhances its interaction with BRD4, promoting anti-apoptotic and pro-proliferative gene expression. This pathway represents a potential therapeutic target for STAT3-dependent diseases.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Signal Transducers and Activator of Transcription-3 (STAT3) are key transcription factors regulated by post-translational modifications (PTMs).
  • STAT3 activation by the IL-6 cytokine superfamily controls cell cycle progression and apoptosis.
  • The specific role of STAT3 mono-ubiquitination in these processes remains largely uncharacterized.

Purpose of the Study:

  • To investigate the consequences of STAT3 mono-ubiquitination.
  • To identify the specific site of STAT3 mono-ubiquitination.
  • To elucidate the functional implications of STAT3 mono-ubiquitination in gene regulation and cellular processes.

Main Methods:

  • Domain mapping and selected reaction monitoring-mass spectrometry to identify ubiquitination sites.
  • Construction of a deubiquitinase-resistant ubiquitinated-STAT3 mimic (ubiquitinated-STAT3 FP).
  • Co-immunoprecipitation assays, chromatin immunoprecipitation, and gene expression analysis (qPCR, Western blotting).

Main Results:

  • Lysine 97 (K97) in the NH2-terminal domain was identified as the primary mono-ubiquitination site on STAT3.
  • Ubiquitinated-STAT3 FP showed enhanced complex formation with bromodomain-containing protein 4 (BRD4).
  • STAT3 mono-ubiquitination promoted BRD4 recruitment to the SOCS3 gene promoter, enhancing STAT3-dependent transcription.
  • Expression of ubiquitinated-STAT3 FP upregulated anti-apoptotic (BCL2, BCL2L1, APEX1, SOD2) and pro-proliferative (CCND1, MYC) genes.
  • Ubiquitinated-STAT3 FP suppressed TNFα-induced apoptosis.

Conclusions:

  • STAT3 mono-ubiquitination at K97 is a critical regulatory event.
  • Mono-ubiquitinated STAT3 enhances BRD4-dependent transcription, driving anti-apoptotic and pro-proliferative gene expression programs.
  • The STAT3 mono-ubiquitination-BRD4 pathway is a potential therapeutic target for STAT3-dependent proliferative diseases.
Keywords:
ApoptosisBRD4Mono-ubiquitinationProliferationSTAT3

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