KRAS and infection: We confirmed that the observed FPN1 cleavage by HCV NS3-4A was not an artifact of ectopic expression of FPN1 (Fig 4E), because cleaved FPN1 protein not seen in uninfected cells was endogenously detected in HCV-infected cells at 3 days post-infection, and the level of full-length FPN1 decreased accordingly (lane 2 vs. lane 3).