We determined that, in contrast to the WT TDP2 cells, the virus-infected KO cells did not possess any discernible VPg unlinkase activity (Figure 6, compare lanes 2 and 4), demonstrating that the activation of a redundant 5′ phosphodiesterase is not responsible for the recovered virus growth observed late during poliovirus infection. Here, TDP2 is linked to poliovirus infection.