This promoter contains the Tet response element (TRE), consisting of seven copies of the 42-bp ...???Leakiness??? and inducibility of dnMEK expression in the dnMEK/CD2-rtTA mice was tested in various tissues including heart, lung, kidney, brain, thymus and spleen by real-time RT-PCR and primers specific for the dnMEK in mice with and without doxycycline.