To assess the DUB and deISGylase activity of the OTU mutants, Huh7 cells were co-transfected with plasmids expressing HA-Ub or V5-ISG15, Ube1L, UbcH8 and HERC5. Cell lysates were harvested 2 days post transfection, and proteins analyzed for Ub- or ISG15-conjugates. The OTU activities of both the single OTU domain (A) and the OTU in the context of the complete L protein were assessed by western blot (B). (C) The cellular levels of CCHFV L protein, co-expressed with HA-Ub or ISG15, were analyzed in Huh7 cells by western blot.