The tet-off system for AML1-ETO transcriptional control.

The tet-off system relies on 2 different DNA constructs. The first construct consists of a fusion of the wild-type tet repressor (TetR) DNA binding domain and the VP16 activation domain of herpes simplex virus driven by the promoter from the murine mammary tumor virus (pMMTV-tTA). The second construct in the system consists of the tetracycline-responsive element (TRE) just upstream from the minimal promoter of the human cytomegalovirus (CMV) driving transcription of AML1-ETO (pUHD–AML1-ETO). In the absence of tetracycline, the tet-controlled transcriptional activator (tTA), which consists of the TetR-VP16 complex, binds the TRE and activates transcription of AML1-ETO. When tetracycline is added, it binds tTA and causes a change in the conformation of the DNA-binding domain of the tet repressor. This prevents tTA from binding to the TRE and AML1-ETO transcription stops.