It can be phosphorylated in vitro by PRKDC/DNA-PK in the presence of Ku and DNA, and by CDC2., subcellular location:Also present in PML nuclear bodies. Redistributes to discrete nuclear foci upon DNA damage., subunit:Heterotrimer of 70, 32 and 14 kDa chains. The DNA-binding activity may reside exclusively on the 70 kDa subunit. Binds to SERTAD3/RBT1. Interacts with TIPIN.,