PRKDC and viral infectious disease: Foreign or fragmented double-strand DNA (dsDNA) in the cytosol caused by viral infections or DNA damage is recognized by the DNA sensor DNA-PKcs (DNA-dependent protein kinase catalytic subunit), which phosphorylates and activates the enzyme cGAS (cyclic GMP-AMP [cGAMP] synthase)49 to produce the cyclic dinucleotide 2′,3′-cGAMP.