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Characterization of growth suppressive functions of a splice variant of cyclin D2

Karim Wafa1, Jessica MacLean, Feixiong Zhang

  • 1Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia, Canada.

Plos One
|January 18, 2013
PubMed

Insights

A novel cyclin D2 splice variant (cycD2SV) forms protein aggregates, inhibiting cell proliferation and causing sensitivity to cell death. This variant may sequester and degrade cell cycle proteins like cyclin D2 and CDK4.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • Cyclin D2 is a key regulator of the cell cycle.
  • Alternative splicing can generate protein variants with altered functions.
  • Understanding novel splice variants is crucial for cell cycle regulation research.

Purpose of the Study:

  • To characterize a newly identified cyclin D2 splice variant, cycD2SV.
  • To investigate the functional consequences of cycD2SV overexpression in immortalized cell lines.
  • To elucidate the mechanisms underlying cycD2SV-mediated cell cycle inhibition.

Main Methods:

  • Cloning and overexpression of cycD2SV.
  • Immunofluorescence and ultrastructural analysis for protein localization.
  • Secondary structure and deletion analysis for protein conformation and function.
  • Co-immunoprecipitation to identify binding partners.
  • Gene expression analysis (mRNA levels) and TUNEL assays.

Main Results:

  • cycD2SV overexpression induced ubiquitinated protein aggregates in various subcellular compartments.
  • cycD2SV exhibited a potentially misfolded conformation and mediated cell cycle inhibition.
  • cycD2SV interacted with endogenous cyclin D2 and CDK4.
  • Upregulation of GADD45α and dynamin 2 mRNA was observed.
  • Cells overexpressing cycD2SV showed increased sensitivity to external stressors but not apoptosis.

Conclusions:

  • cycD2SV induces cell cycle arrest and protein aggregation.
  • The N-terminal region (1-53 aa) is implicated in aggregation, while the C-terminal region (54-136 aa) mediates cell cycle inhibition.
  • cycD2SV may inhibit cell cycle progression by sequestering and promoting degradation of cyclin D2 and CDK4.
  • The variant sensitizes cells to stress-induced death, suggesting a role in cellular stress response pathways.

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