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Canine Ku70 requires binding between its nuclear localization signal and nuclear pore-targeting complex for nuclear

Manabu Koike1,2,3, Togo Ikuta4, Aki Koike3

  • 1QST hospital, National Institutes for Quantum Science and Technology, Chiba, Japan.

The Journal of Veterinary Medical Science
|July 9, 2025
PubMed

Insights

Canine Ku70 protein is imported into the nucleus via importin-α/β, a conserved mechanism across species. Ku80 is crucial for canine Ku70 accumulation at DNA double-strand breaks (DSBs).

Area of Science:

  • Molecular Biology
  • Genetics
  • Cell Biology

Background:

  • Subcellular localization and regulation of DNA repair proteins are key to understanding genotoxicity.
  • Dysregulation of DNA repair proteins, like Ku70/Ku80 in non-homologous end joining (NHEJ), is linked to diseases and sensitivity to mutagens.
  • The nuclear import mechanism of canine Ku70, essential for DNA double-strand break (DSB) repair, was previously unclear.

Purpose of the Study:

  • To elucidate the mechanism of nuclear localization for canine Ku70.
  • To investigate the role of Ku80 in canine Ku70's function at DSBs.
  • To explore the conservation of canine Ku70 nuclear import mechanisms across species.

Main Methods:

  • Transfection of EYFP-canine Ku70 into various cell lines (canine, human, hamster, mouse).
  • Analysis of nuclear localization using fluorescence microscopy.
  • Investigation of importin-α/β binding to Ku70's predicted nuclear localization signal.
  • Assessment of Ku80's role in Ku70 accumulation at DSBs.

Main Results:

  • Experimental evidence confirmed canine Ku70 localizes to the nucleus.
  • The nuclear localization signal of canine Ku70 binds to the importin-α/β complex.
  • EYFP-canine Ku70 was successfully imported into the nucleus of human, hamster, and mouse cells, indicating a conserved mechanism.
  • Ku80 was found to be essential for the accumulation of canine Ku70 at DSBs.

Conclusions:

  • Canine Ku70 is imported into the nucleus via a conserved importin-α/β-dependent pathway.
  • Ku80 plays a critical role in recruiting canine Ku70 to sites of DNA damage.
  • These findings provide foundational knowledge for understanding Ku70 regulation and DSB-induced genotoxicity in dogs.
Keywords:
Ku70Ku80doglocalization

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