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14-3-3ζ interacts with DNA-binding domain of FOXO3a and competitively dissociates DNA by dual-motif tethering

Shota Enomoto1, Tomoya Kuwayama1, Shoichi Nakatsuka1

  • 1Graduate School of Pharmaceutical Sciences, Keio University 1-5-30 Shibakoen, Minato-ku, Tokyo, Japan.

Nature Communications
|February 16, 2026
PubMed

Insights

14-3-3ζ protein binding to phosphorylated FOXO3a (a tumor suppressor) displaces it from DNA, halting apoptosis. This study reveals 14-3-3ζ directly competes for DNA binding, suppressing cancer cell proliferation.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Cancer Research

Background:

  • Ras mutations in cancer activate signaling pathways promoting cell proliferation.
  • FOXO3a is a transcription factor that induces apoptosis, but is often inactivated in cancer.
  • In cancer cells, FOXO3a is phosphorylated and bound by 14-3-3ζ, leading to its displacement from DNA and suppressed apoptosis.

Purpose of the Study:

  • To elucidate the mechanism by which 14-3-3ζ binding displaces FOXO3a from DNA.
  • To investigate the direct interaction between 14-3-3ζ and FOXO3a's DNA-binding domain (DBD).

Main Methods:

  • Isothermal titration calorimetry (ITC) to measure binding affinities.
  • Fluorescence-detection size-exclusion chromatography (FSEC) to assess complex formation.
  • Nuclear magnetic resonance (NMR) spectroscopy to identify interaction sites.

Main Results:

  • 14-3-3ζ strongly displaces DNA from di-phosphorylated FOXO3a (dpFOXO3a).
  • Direct, albeit weak, binding of 14-3-3ζ to the FOXO3a DBD was observed via NMR.
  • This suggests a competitive binding mechanism where 14-3-3ζ binds to both phosphorylation sites and the DBD.

Conclusions:

  • 14-3-3ζ binding to FOXO3a involves dual tethering: interaction with phosphorylation sites and direct competition at the DBD.
  • This dual interaction mechanism enhances 14-3-3ζ's ability to displace FOXO3a from DNA, thereby suppressing apoptosis and promoting cancer cell survival.
  • Understanding this mechanism offers potential therapeutic targets for reactivating FOXO3a-mediated apoptosis in cancer.

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