EF-1 alpha promoter versions of the Tet-On 3G Tetracycline Inducible Expression System provide for consistent long-term expression of the Tet-On 3G transactivator, even in cell types known for their tendency to silence a CMV promoter over time, such as hematopoietic cells and stem cells. This means that in these cell types long term tetracycline inducible expression can be achieved. The systems contain the same pTRE3G vectors as our standard Tet-On 3G Systems that generate the lowest possible background expression; however the Tet-On 3G transactivator is expressed from an EF1-alpha promoter instead of a CMV promoter. The EF-1 alpha promoter in these systems is derived from the human EEF1A1 gene that expresses the alpha subunit of eukaryotic elongation factor 1.
We tested the EF-1 alpha version in Jurkat cells, a cell line known to show reduced expression and clonal variation in expression from CMV-based vectors. When expressing the Tet-On 3G transactivator protein from the EF-1 alpha promoter, 83% of the Jurkat Tet-On 3G clones showed strong inducible expression and 33% demonstrated very high inducibility (greater than 2,000-fold). Such levels of control are not possible when using previous versions of the Tet-On system for this cell line.
