Ku70/Ku80 proteins function in
After double-strand break, Ku heterodimer comprising Ku70 and Ku80 forms ring-shaped structure that threads onto each DNA end with high affinity irrespective of sequence, protecting ends from excessive resection. Ku serves as scaffold recruiting DNA-dependent protein kinase catalytic subunit, end-processing factors, and Ligase IV complex. By blocking homologous recombination machinery, Ku channels repair toward NHEJ, especially in mammalian G1 cells or immune lymphocytes generating immunoglobulin diversity. Absence of Ku shifts repair toward microhomology-mediated alternative end joining or homologous recombination pathways, increasing resection length and genome instability.
Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 12: Ku70 Ku80 Function in NHEJ Pathway