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Speedy/Ringo C regulates S and G2 phase progression in human cells

Aiyang Cheng1, Mark J Solomon

  • 1Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, Connecticut 06520-8024, USA.

Cell Cycle (Georgetown, Tex.)
|September 20, 2008
PubMed

Insights

Speedy/Ringo C proteins regulate cell cycle progression. This study shows Speedy/Ringo C promotes cell division by shortening G2 phase and enhancing S phase progression in human cells.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Biochemistry

Background:

  • Cyclin-dependent kinases (CDKs) are key regulators of the cell cycle.
  • Speedy/Ringo (S/R) proteins represent a distinct class of CDK activators.
  • The specific functions of mammalian S/R protein family members are largely unknown.

Purpose of the Study:

  • To investigate the cell cycle roles of human Speedy/Ringo C.
  • To determine the impact of Speedy/Ringo C on cell cycle progression in HEK293 cells.

Main Methods:

  • RNA interference (RNAi) for Speedy/Ringo C down-regulation.
  • Ectopic expression of Speedy/Ringo C.
  • Double thymidine arrest and release experiments.
  • A novel three-color Fluorescence-Activated Cell Sorting (FACS) protocol to measure G2 phase length.

Main Results:

  • Speedy/Ringo C down-regulation by RNAi delayed S and G2 phase progression.
  • Ectopic Speedy/Ringo C expression reduced S and G2/M populations and promoted late S phase progression.
  • Speedy/Ringo C suppression prolonged G2 phase by ~30 min; ectopic expression shortened it by ~25 min.
  • Overexpression of Speedy/Ringo C disrupted the G2 DNA damage checkpoint, increased cell death, and caused a G1-to-S transition delay.

Conclusions:

  • CDK-Speedy/Ringo C complexes positively regulate cell cycle progression.
  • Speedy/Ringo C plays a critical role in late S and G2 phase progression.
  • Speedy/Ringo C influences G2 phase length and the DNA damage checkpoint.

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