Effect of pUL50 expression on levels of ISGylation. 293T cells in six-well plates were cotransfected with plasmids (0.25 μg) expressing Myc-ISG15GG, HA-UBE1L, Flag-UbcH8, and HA-Herc5 and increasing amounts (0.2, 0.5, and 1 μg) of a plasmid expressing SRT-pUL50, as indicated. Forty-eight hours after transfection, cell lysates were prepared and subjected to immunoblotting with anti-Myc or anti-SRT antibody. Levels of β-actin are shown as a loading control.