Murine Tcf3 cDNA was tagged with an amino-terminal C-myc epitope to distinguish it from endogenous Tcf3. This tagged cDNA was placed under control of a tetracycline regulatory element (TRE) and a CMV minimal promoter. A rabbit beta globin intron was located between the TRE/CMV promoter sequences and the Tcf3 cDNA. The 3' beta-globin UTR was located downstream of the Tcf3 sequence. (J:116057)