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The RNA-binding protein Sam68 modulates the alternative splicing of Bcl-x

Maria Paola Paronetto1, Tilman Achsel, Autumn Massiello

  • 1Department of Public Health and Cell Biology, Section of Anatomy, University of Rome Tor Vergata, 00133 Rome, Italy.

The Journal of Cell Biology
|March 21, 2007
PubMed

Insights

The RNA-binding protein Sam68 regulates Bcl-x alternative splicing, influencing apoptosis. Tyrosine phosphorylation switches Sam68’s role from pro- to anti-apoptotic, impacting cell fate.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • The RNA-binding protein Sam68 is implicated in apoptosis, but its specific mRNA targets and regulatory mechanisms are not fully understood.
  • Understanding Sam68's function is crucial for deciphering cellular pathways controlling programmed cell death.

Purpose of the Study:

  • To identify Sam68's mRNA targets and elucidate its mechanism of action in regulating apoptosis.
  • To investigate the role of Sam68 in the alternative splicing of Bcl-x mRNA.

Main Methods:

  • RNA interference (RNAi) for Sam68 depletion and up-regulation.
  • Analysis of Bcl-x alternative splicing.
  • Tyrosine phosphorylation assays using Fyn kinase.
  • Mutational analysis of Sam68's RNA-binding domain.
  • Coexpression studies with ASF/SF2 and hnRNP A1.

Main Results:

  • Sam68 directly binds Bcl-x mRNA and regulates its alternative splicing.
  • Sam68 depletion increases anti-apoptotic Bcl-x(L); Sam68 up-regulation increases pro-apoptotic Bcl-x(s).
  • Tyrosine phosphorylation of Sam68 by Fyn favors Bcl-x(L) splicing, while interaction with hnRNP A1 promotes Bcl-x(s) splicing.

Conclusions:

  • Sam68 is a key regulator of Bcl-x alternative splicing, influencing the balance between pro- and anti-apoptotic isoforms.
  • Tyrosine phosphorylation of Sam68 by Src-like kinases acts as a switch, modulating its function in apoptosis from pro- to anti-apoptotic.
  • Sam68's interaction with hnRNP A1 is critical for its role in promoting Bcl-x(s) splicing.

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