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Phosphorylation of the alternative mRNA splicing factor 45 (SPF45) by Clk1 regulates its splice site utilization,

Yuying Liu1, LaShardai Conaway, Jennifer Rutherford Bethard

  • 1Department of Cell and Molecular Pharmacology and Experimental Therapeutics, Medical University of South Carolina, 173 Ashley Ave, Charleston, SC 29425, USA.

Nucleic Acids Research
|March 23, 2013
PubMed

Insights

Cdc2-like kinase 1 (Clk1) regulates alternative splicing factor 45 (SPF45) activity, impacting cancer cell migration and invasion. This study reveals Clk1

Area of Science:

  • Molecular Biology
  • Cancer Biology
  • Biochemistry

Background:

  • Alternative mRNA splicing regulates protein isoforms and is controlled by splicing factors.
  • The splicing factor SPF45 is overexpressed in cancer, but its functions and targets are largely unknown.
  • Previous work linked SPF45 phosphorylation by ERK2 to cell proliferation and fibronectin adhesion.

Purpose of the Study:

  • To investigate the role of Clk1 in regulating SPF45.
  • To identify the functional consequences of Clk1-mediated SPF45 phosphorylation on alternative splicing and cancer cell behavior.
  • To elucidate the mechanism by which Clk1 influences SPF45 protein stability and activity.

Main Methods:

  • Phosphorylation site analysis of SPF45 by Clk1.
  • Mutational analysis of Clk1 phosphorylation sites on SPF45.
  • Assessment of splicing activity, mRNA binding, and protein degradation.
  • Evaluation of cancer cell migration and invasion assays.

Main Results:

  • Clk1 phosphorylates SPF45 on eight serine residues, influencing alternative splicing of Fas mRNA.
  • Mutational analysis revealed complex regulatory effects of Clk1 phosphorylation on SPF45 splicing activity.
  • Clk1 enhances SPF45 protein expression by inhibiting proteasomal degradation and promotes ovarian cancer cell migration and invasion.
  • SPF45 overexpression, particularly phospho-mimetic mutants, stimulates invasion, fibronectin expression, ERK activation, and cortactin phosphorylation.

Conclusions:

  • Clk1 plays a critical role in regulating SPF45 activity and stability.
  • SPF45 overexpression, biochemically regulated by Clk1, enhances cancer cell migration and invasion.
  • This study provides novel insights into the molecular mechanisms underlying SPF45 function in cancer progression.

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