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ATM phosphorylates PP2A subunit A resulting in nuclear export and spatiotemporal regulation of the DNA damage

Amrita Sule1,2, Sarah E Golding1, Syed F Ahmad1,2

  • 1Department of Radiation Oncology, Virginia Commonwealth University, Richmond, VA, 23298-0058, USA.

Cellular and Molecular Life Sciences : CMLS
|November 26, 2022
PubMed

Insights

The phosphorylation of PR65 by ATM is crucial for DNA damage response and repair. This single amino acid change impacts cell survival and growth by controlling protein movement within the cell.

Area of Science:

  • Cellular Biology
  • Molecular Biology
  • Genetics

Background:

  • Ataxia telangiectasia mutated (ATM) is a key regulator of the DNA damage response (DDR).
  • Protein phosphatase 2A (PP2A) subunit PR65, specifically at serine 401 (S401), is a critical target of ATM.
  • PP2A regulates mitosis, cell growth, and protein dephosphorylation during DDR recovery.

Purpose of the Study:

  • To investigate the role of PR65 phosphorylation at S401 in the DNA damage response.
  • To determine how ATM-mediated phosphorylation of PR65 impacts DNA double-strand break (DSB) repair, cell survival, and growth.
  • To elucidate the mechanism of PR65 nuclear-cytoplasmic shuttling in response to DNA damage.

Main Methods:

  • Generated mouse embryonic fibroblasts expressing wild-type (WT), S401A (non-phosphorylatable), and S401D (phospho-mimetic) PR65 transgenes.
  • Assessed chromosomal aberrations, DSB repair (nonhomologous end joining and homologous recombination), and radiation survival.
  • Utilized time-lapse video microscopy and cellular localization experiments to track PR65 dynamics.
  • Identified and mutated a putative nuclear export sequence (NES) near S401.

Main Results:

  • PR65 S401 mutants (S401A and S401D) exhibited significant chromosomal aberrations and impaired DSB repair.
  • Mutant cells showed delayed DNA damage recovery and reduced survival following radiation exposure.
  • S401D cells displayed increased ERK and AKT signaling, leading to enhanced growth rates.
  • PR65 was exported to the cytoplasm post-radiation via CRM1, a process dependent on a functional NES near S401.

Conclusions:

  • Phosphorylation of PR65 at S401 by ATM is a fundamental control point for the DNA damage response.
  • ATM-PP2A signaling balances DSB repair, cell survival, and growth.
  • Spatiotemporal control of PR65 shuttling by CRM1, regulated by S401 phosphorylation, is critical for these processes.
Keywords:
CRM1DNA repairHS-AFMMitotic catastropheNuclear exportRadiation

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