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G2 DNA damage checkpoint inhibition and antimitotic activity of 13-hydroxy-15-oxozoapatlin

N T Rundle1, L Xu, R J Andersen

  • 1Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.

The Journal of Biological Chemistry
|September 27, 2001
PubMed

Insights

13-hydroxy-15-oxozoapatlin (OZ), a compound from Parinari curatellifolia, inhibits the G(2) cell cycle checkpoint. It also acts as an antimitotic agent, arresting cells in mitosis, and shows potential in cancer therapy.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Pharmacology

Background:

  • DNA damage triggers cell cycle checkpoints, arresting cells in G(1) and G(2) phases.
  • G(2) checkpoint inhibitors are valuable tools for studying DNA damage response and enhancing cancer therapies, especially in p53-deficient cancers.

Purpose of the Study:

  • To screen for novel G(2) checkpoint inhibitors from natural products.
  • To characterize the mechanism of action of identified compounds, specifically 13-hydroxy-15-oxozoapatlin (OZ).

Main Methods:

  • Utilized a cell-based assay to screen extracts from the NCI Natural Products Repository.
  • Employed flow cytometry with a mitosis-specific antibody to assess G(2) checkpoint inhibition.
  • Performed in vitro assays to evaluate the inhibition of key cell cycle regulatory proteins (ATM, ATR, Chk1, Chk2, Plk1, phosphatases).

Main Results:

  • Identified 13-hydroxy-15-oxozoapatlin (OZ) from *Parinari curatellifolia* as a G(2) checkpoint inhibitor.
  • OZ maximally inhibited the G(2) checkpoint at 10 microm, releasing irradiated MCF-7 (p53-defective) and HCT116p53(-/-) cells from arrest.
  • OZ exhibited additive effects with isogranulatimide and debromohymenialdisine but not UCN-01 or caffeine; it did not inhibit major kinases or phosphatases.
  • OZ induced a prometaphase-like mitotic arrest with condensed, scattered chromosomes and disordered spindles.

Conclusions:

  • OZ functions as a G(2) checkpoint inhibitor and an antimitotic agent.
  • OZ's unique mechanism, distinct from known kinase/phosphatase inhibition, warrants further investigation for therapeutic applications in cancer.

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