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p53 localization at centrosomes during mitosis and postmitotic checkpoint are ATM-dependent and require serine 15

A Tritarelli1, E Oricchio, M Ciciarello

  • 1Istituto di Biologia e Patologia Molecolari Consiglio Nazionale delle Ricerche, 00185 Rome, Italy.

Molecular Biology of the Cell
|June 8, 2004
PubMed

Insights

ATM kinase is crucial for the tumor suppressor p53 to localize at centrosomes during mitosis. This ATM-dependent p53 localization is essential for the postmitotic checkpoint, preventing DNA reduplication after spindle disruption.

Area of Science:

  • Cell Biology
  • Molecular Biology
  • Cancer Research

Background:

  • The p53 oncosuppressor protein normally localizes to centrosomes during mitosis.
  • This association is disrupted by agents that depolymerize microtubules.
  • ATM is a key kinase activated by DNA damage and upstream of p53.

Purpose of the Study:

  • To investigate the role of ATM in p53 centrosomal localization.
  • To determine if ATM-dependent p53 localization is required for the postmitotic checkpoint.
  • To elucidate the mechanism of p53 regulation at centrosomes during mitosis.

Main Methods:

  • Utilized ATM-deficient cell lines (ataxia-telangiectasia) and p53-null cells.
  • Employed gene transfer to reintroduce wild-type ATM and p53.
  • Used phosphatase inhibitors and spindle inhibitors (nocodazole) to disrupt and analyze p53 localization and phosphorylation.
  • Assessed postmitotic proliferation arrest.

Main Results:

  • p53 failed to localize to centrosomes in ATM-deficient cells, but wild-type ATM gene transfer restored localization.
  • A specific p53 mutant (p53-S15A), unphosphorylatable by ATM, did not localize to centrosomes.
  • Serine 15 phosphorylation of p53 was detected at centrosomes upon phosphatase inhibition, indicating a role for dephosphorylation in sustaining the cell cycle.
  • p53 dissociated from centrosomes and remained phosphorylated at Ser15 upon spindle disruption.
  • ATM-deficient cells failed to arrest proliferation after spindle disruption and release.

Conclusions:

  • ATM kinase is essential for the correct localization of p53 to centrosomes during mitosis.
  • ATM-dependent p53 centrosomal localization and subsequent regulation are critical for activating the postmitotic checkpoint.
  • These findings reveal a surveillance mechanism involving p53 and ATM that inhibits DNA reduplication downstream of the spindle assembly checkpoint.

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