RHO and infection: To determine whether Rho is activated by infection with Y. pseudotuberculosis, we infected HeLa cells with strain yopEHJ (YP27) for 5, 10, 15 and 20 min and we analyzed the amount of active Rho (GTP-Rho) in the cell lysates by a GTP-Rho pull-down assay, as described in Material and Methods.