DNA requirements for interaction of the C-terminal region of Ku80 with the DNA-dependent protein kinase catalytic subunit (DNA-PKcs).

•The length and base composition of DNA ends affects Ku70/80-DNA-PKcs complex assembly.•Ku80CTR is required for assembly of Ku70/80 and DNA-PKcs on blunt ended 25 bp DNA and 25 bp dsDNA with a poly dA ssDNA extension but not 25 bp dsDNA with a poly dT or poly dC ssDNA extension.•The optimal scaffold for assembly of the Ku70/80-DNA-PKcs complex is dsDNA with a poly pyrimidine ssDNA extension.