rtTA2SM2

rtTA2S-M2 is a second-generation reverse tetracycline-controlled transactivator used to achieve doxycycline-inducible gene expression in mammalian cells and organisms. It is employed in the Tet-On system, where gene expression is turned on by doxycycline in cells that express rtTA2S-M2 and contain a tetracycline-responsive element (TRE)–driven reporter or gene of interest.

Mechanism and regulation: The rtTA2S-M2 protein binds to the TRE only in the presence of doxycycline. Upon binding, it activates transcription through its activation domain, driving expression of the downstream gene. In the absence of doxycycline, rtTA2S-M2 has little affinity for TRE, resulting in minimal basal transcription and tighter off-state control.

Properties and performance: Compared with earlier rtTA variants, rtTA2S-M2 generally offers higher sensitivity to doxycycline, stronger transcriptional activation, and lower basal activity across various cell types. These attributes enable more robust induction and finer control of expression, often allowing effective activation at lower doxycycline concentrations and with reduced background.

Applications: rtTA2S-M2 is widely used in cell lines and transgenic models to inducibly express reporters, functional proteins, or genome editing components. It is compatible with various TRE-promoter configurations and can be combined with tissue- or development-specific promoters, as well as with other genetic systems for refined control or intersectional strategies.

Notes: The designation rtTA2S-M2 (also seen as rtTA2SM2) refers to the same second-generation variant. While it reduces leak relative to earlier versions, some background expression can persist depending on promoter context, copy number, and doxycycline availability in vivo or in culture.