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In Vitro SUMOylation Assay to Study SUMO E3 Ligase Activity
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In Vitro SUMOylation Assay to Study SUMO E3 Ligase Activity

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SUMOylation of Csk Negatively Modulates its Tumor Suppressor Function

Nan Cui1, Tianqi Liu1, Yanmin Guo1

  • 1Department of Biochemistry and Molecular Cell Biology, Shanghai Key Laboratory of Tumor Microenvironment and Inflammation, Shanghai Jiao Tong University School of Medicine (SJTU-, SM), Shanghai, 200025, China.

Neoplasia (New York, N.Y.)
|May 25, 2019
PubMed

Insights

Csk SUMOylation at lysine 53 negatively regulates its tumor suppressor function. This modification by PIAS3 reduces Csk binding to Cbp, activating c-Src and promoting tumor cell growth.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Oncology

Background:

  • Csk is a tyrosine kinase that negatively regulates Src family kinases (SFKs).
  • Regulation of Csk expression is poorly understood.
  • SUMOylation is a post-translational modification impacting biological processes, including tumor progression.

Purpose of the Study:

  • To investigate the regulation of Csk expression and function.
  • To identify modifications affecting Csk activity and its role in tumor progression.

Main Methods:

  • In vitro and in vivo SUMOylation assays.
  • Identification of SUMO E3 ligase using PIAS3.
  • Site-directed mutagenesis (K53R mutant).
  • Analysis of protein-protein interactions (Csk-Cbp).
  • Assessment of c-Src phosphorylation.
  • Cell growth assays.

Main Results:

  • Csk is SUMOylated by SUMO1 at lysine 53 (K53).
  • PIAS3 is identified as the primary SUMO E3 ligase for Csk.
  • SUMOylation of Csk at K53 impairs its interaction with Csk binding protein (Cbp).
  • This interaction defect leads to decreased c-Src phosphorylation at Y527.
  • SUMO-defective Csk (K53R) mutant inhibited tumor cell growth more effectively than wild-type Csk.

Conclusions:

  • SUMOylation of Csk, primarily at K53, negatively modulates its tumor suppressor function.
  • This SUMOylation reduces Csk binding to Cbp, leading to c-Src activation.
  • Targeting Csk SUMOylation may offer therapeutic strategies for cancer.

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