Diagram of transgenes. The Vav-tTA transgene consists of the 2.3-kb Vav promoter region, the tTA sequence, and 2 enhancer regions of 0.7 and 3.7 kb. The tetracycline-responsive transgene is composed of TRE2, the human NRAS coding sequence containing a G>V mutation at codon 12, then the EMCV IRES and a truncated human CD2 lacking the intracellular signaling portion of the molecule. Arrows indicate primer annealing sites for PCR and RT-PCR.