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Cdk1-mediated threonine phosphorylation of Sam68 modulates its RNA binding, alternative splicing activity and

Idir Malki1, Inara Liepina1, Nora Kogelnik1

  • 1The Leicester Institute of Structural and Chemical Biology and Department of Molecular and Cell Biology, University of Leicester, Leicester LE1 7RH, UK.

Nucleic Acids Research
|December 20, 2022
PubMed

Insights

Sam68 protein phosphorylation by Cdk1 at T33 and T317 regulates its RNA binding and localization. This impacts alternative splicing, reducing apoptosis and increasing proliferation in HCT116 cells.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • Sam68 (KHDRBS1) is a STAR family protein linking signal transduction to post-transcriptional gene regulation.
  • Sam68 modulates alternative splicing of oncogenic proteins, with its function affected by cell cycle-dependent post-translational modifications like phosphorylation.
  • The molecular mechanisms underlying these modulations are not well understood.

Purpose of the Study:

  • To comprehensively map post-translational modifications of Sam68 across different cell cycle stages.
  • To elucidate the molecular basis and mechanisms of Sam68 modulation by phosphorylation.

Main Methods:

  • Combined mass spectrometry, nuclear magnetic resonance spectroscopy, and cell biology techniques.
  • Analysis performed in HEK293 and HCT116 cell lines at various cell cycle stages.

Main Results:

  • Identified specific phosphorylation of Sam68 at T33 and T317 by Cdk1.
  • Demonstrated that T33/T317 phosphorylation reduces Sam68's RNA binding affinity and alters its cellular localization.
  • Showed that these phosphorylation events decrease Sam68's alternative splicing activity.

Conclusions:

  • Cdk1-mediated phosphorylation of Sam68 at T33 and T317 is a key regulatory mechanism.
  • This phosphorylation directly impacts Sam68's function in RNA binding and alternative splicing.
  • Reduced Sam68 splicing activity leads to decreased apoptosis and increased proliferation in HCT116 cells.

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