EGGDVDDLLDMI polypeptides having the ability to bind to a DNA-PKcs-like polypeptide will have the ability to modulate, e.g. interfere with, binding of that DNA-PKcs-like poylpeptide to proteins harbouring that EGGDVDDLLDMI polypeptide or variants thereof, e.g. to proteins which are in vivo binding partners of that DNA-PKcs-like polypeptide.