Features:The tetracycline-inducible system, tTA, is a protein formed by the fusion of TetR and the viral transcription activation domain VP16. Under physiological conditions, tTA actively binds to the TRE, initiating gene expression. However, if doxycycline (Dox) is administered, the binding of Dox to tTA causes dissociation from the TRE, thereby inhibiting gene expression. IBIST is a modification where tTA is split into two halves, and the regulatory function is only restored when the two protein halves bind together to form the correct tTA structure.