Infection of NIH3T3 cells (wildtype for Tsg101) with AdCre did not lead to an elevation of activated MAP kinases (Fig. 1F, lanes 1 and 2), suggesting that the increase in pErk1/2 levels in AdCre-infected Tsg101fl/fl MEFs was not due to adenovirus infection per se but rather due to the lack of Tsg101. Here, TSG101 is linked to infection.