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Mitotic DNA damage response: Polo-like kinase-1 is dephosphorylated through ATM-Chk1 pathway

Hee-Jae Lee1, Hyo-In Hwang, Young-Joo Jang

  • 1Laboratory of Cell Cycle & Signal Transduction, World Class University Research Department of Nanobiomedical Science, and Institute of Tissue Regeneration Engineering, Dankook University, Cheonan, Korea.

Cell Cycle (Georgetown, Tex.)
|June 29, 2010
PubMed

Insights

DNA damage in dividing cells activates ATM/ATR kinases, halting cell growth. A novel ATM/Chk1/PP2A pathway regulates Plk1 dephosphorylation, crucial for mitotic DNA damage checkpoints and cell cycle arrest.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Genetics

Background:

  • DNA damage during the cell cycle triggers checkpoint pathways involving ATM/ATR kinases.
  • Mitotic DNA damage typically causes cells to arrest in a G2-like phase, preventing entry into mitosis.
  • Mitosis-specific kinases like Cdk1 and Plk1 are regulated during this checkpoint response.

Purpose of the Study:

  • To elucidate the molecular mechanisms underlying the mitotic DNA damage checkpoint.
  • To identify the kinases and phosphatases involved in regulating Plk1 activity during mitotic DNA damage.
  • To investigate the role of ATM/Chk1 and Protein Phosphatase 2A (PP2A) in this cellular response.

Main Methods:

  • Doxorubicin treatment to induce DNA damage in mitotic cells.
  • Small hairpin RNA (shRNA) to deplete ATM and Chk1 expression.
  • Knockdown of Protein Phosphatase 2A (PP2A) catalytic subunits.
  • Overexpression of PP2A.
  • Analysis of cell cycle progression (G2-like arrest vs. G1 entry).
  • Assessment of Plk1 phosphorylation and degradation.

Main Results:

  • Mitotic DNA damage induced G2-like cell cycle arrest, dependent on ATM/Chk1 activity.
  • ATM/Chk1 activity led to Plk1 dephosphorylation and inhibition.
  • Protein Phosphatase 2A (PP2A) was identified as the key phosphatase responsible for Plk1 dephosphorylation.
  • PP2A knockdown resulted in Plk1 degradation instead of dephosphorylation, bypassing G2 arrest.
  • Overexpression of PP2A counteracted ATM/Chk1 inhibition, suggesting PP2A acts downstream or dominantly in the pathway.
  • This ATM/Chk1/PP2A pathway functions independently of p53.

Conclusions:

  • Negative regulation of Plk1 by dephosphorylation via the ATM/Chk1/PP2A pathway is critical for G2-like cell cycle arrest at the mitotic DNA damage checkpoint.
  • This pathway represents a novel mechanism for cellular response to mitotic DNA damage, independent of p53.
  • Understanding this pathway provides insights into cell cycle regulation and DNA repair fidelity.

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