DNA-dependent protein kinase, catalytic subunit, also known as DNA-PKcs, is an enzyme that belongs to the phosphatidylinositol 3-kinase-related kinase protein family. Anderson and Lees-Miller (1992) noted that DNA-PK had been shown in vitro to phosphorylate several transcription factors, suggesting that it functions in cell homeostasis by modulating transcription. It acts as a molecular sensor for DNA damage, and it may also act as a scaffold protein to aid the localization of DNA repair proteins to the site of damage.