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DNA damage activates a spatially distinct late cytoplasmic cell-cycle checkpoint network controlled by MK2-mediated

H Christian Reinhardt1, Pia Hasskamp, Ingolf Schmedding

  • 1David H. Koch Institute for Integrative Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02132, USA.

Molecular Cell
|October 12, 2010
PubMed

Insights

Cancer cells with defective p53 rely on the p38/MK2 pathway for DNA damage survival. This pathway maintains cell cycle arrest by stabilizing specific mRNAs, crucial for DNA repair.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Cancer Research

Background:

  • Genotoxic stress triggers cellular responses including cell cycle arrest and DNA repair via kinase signaling.
  • p53-defective tumors exhibit altered DNA damage responses, becoming dependent on the p38/MK2 pathway for survival.
  • The ATR-Chk1 pathway is functional in these cells, yet checkpoint control is rewired.

Purpose of the Study:

  • To elucidate the distinct roles of Chk1 and MK2 in DNA damage checkpoint control using functional genetics.
  • To understand the molecular mechanisms underlying the p38/MK2 pathway's contribution to cancer cell survival post-DNA damage.

Main Methods:

  • Functional genetics to investigate Chk1 and MK2 functions.
  • Analysis of protein complex relocalization (p38/MK2) from nucleus to cytoplasm.
  • Assessment of mRNA stabilization and degradation pathways (Gadd45α mRNA).
  • Investigation of protein-protein interactions and phosphorylations (hnRNPA0, TIAR, PARN).

Main Results:

  • Nuclear Chk1 activity is essential for establishing the G(2)/M checkpoint.
  • Cytoplasmic MK2 activity is critical for prolonged checkpoint maintenance via posttranscriptional mRNA stabilization.
  • p38/MK2 complex relocalizes to the cytoplasm upon DNA damage.
  • MK2 stabilizes Gadd45α mRNA by phosphorylating hnRNPA0 and PARN, while p38 releases TIAR.
  • Gadd45α sustains a positive feedback loop, sequestering Cdc25B/C in the cytoplasm to prevent mitotic entry.

Conclusions:

  • The p38/MK2 pathway plays a critical role in the posttranscriptional regulation of gene expression during the DNA damage response in cancer cells.
  • Cytoplasmic MK2 activity is key for maintaining prolonged cell cycle arrest through mRNA stabilization.
  • This pathway represents a potential therapeutic target in p53-defective cancers.

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