ZUP1 and infection: To investigate whether the EBV encoded DUB regulates the proteasomal degradation of poisoned topoisomerases, FLAG-tagged versions of the N-terminal catalytic domain of BPLF1 that is generated by caspase I cleavage of the large tegument protein during productive infection [32], and an inactive mutant where the catalytic Cys61 was substituted with Ala (BPLF1C61A) were stably expressed by lentivirus transduction in HEK-293T cells under the control of a Tet-on regulated promoter (HEK-rtTA-BPLF1/BPLF1C61A cell lines).