Consequently, although inhibition of DNA-PK improved the replication of an E4-mutant Ad even when exerted early during infection, replication of an E4orf4-expressing E4-mutant Ad was improved further when DNA-PK was inhibited only later during infection, allowing E4orf4 to function in collaboration with DNA-PK at the early stage. The gene discussed is PRKDC; the disease is infection.