For any therapeutic intervention, dosing is key.
Consider a system for gas-inducible transcription control composed of a fungal trans-activator (expected to be functional in mammalian cells), AlcR, and an operator, activated by small concentrations of a chemical found in tabacco smoke.
Some of their work (biotechnol bioeng. 83:810 2003) demonstrated that different amounts of the final product is expressed depending on which level of the control cascade is repressed, such that repressing the level directly responsible for expressing the desired product results in very little expression, while repression of increasingly distant levels of the cascade allows more and more expression of the product. This makes sense, as just a little bit of constituative expression or wobble in the initial signalling genes could be magnified though the control cascade.
Digital Electronics - Digital Genetics
input:switch -> Buffer:capacitor -> delay:resistor -> switch:transistor -> output:lamp