Interestingly, infection of HCT116 and DLD-1 with the negative control vectors (hACTB-R and N.P.)elicited PIGA gene targeting with decent efficiencies comparable with those achieved by the use of the CMV promoter, despite that the CMV promoter and the negative controls induced remarkably different levels of long-term gene expression and G418-resistant colony formation (Figs. 2 and 5). Here, PIGA is linked to infection.