Part Collection

Tet-based regulatory elements in mammalian cells

The mammalian cell Tet-Off and Tet-On systems originated from the Tet repressor protein (TetR) and its corresponding tet operator (tetO) DNA elements that control the Tn10-encoded tetracycline resistance operon of Escherichia coli.

Tet-Off system :

Tetracycline transcriptional activator (tTA) is the major transcriptional regulator in the tet-Off system. The tTA protein contains an N-terminal TetR DNA binding domain and a C-terminal VP16 transcriptional activation domain of the herpes simplex virus. In the absence of doxycycline, the tTA protein binds to the tetO sequence on the TCE promoter, thereby activating the downstream gene expression. The administration of doxycycline blocks the binding between tTA and tetO, hence blocking the downstream gene expression.

Figure1:The working mechanism of tet-off system

Tet-On system :

The Tet-On system is based on the Reversed Tetracycline transcriptional activator (rtTA), which carries 4 amino acid mutations on the tetR DNA binding domain of the tTA. In opposite to tTA, the tetO-binding of rtTA is triggered by the presence of doxycycline.Therefore, downstream gene is only activated upon doxycycline stimulation.