Fig. 1

Schematic illustrations of the self-repressing gene circuit (MG::PR-8 T) and the non-self-repressing gene circuit (MG::PR-8 T-P39K). a Two tet operator sequences (TetO₂) inserted downstream of the Ptet promoter are bound by TetR self-repressor dimers. In the absence of aTc (the inducers), TetR-Venus dimers bind to the operators. This interaction prevents the binding of RNA polymerase, thereby inhibiting the TetR-Venus fusion protein synthesis. When aTc diffuse into the cell, they bind to TetR, inducing an allosteric conformational change in the repressor protein which releases it from DNA, allowing for the possibility of the gene being switched into the “on” state. All of these constitute a self-repressing gene circuit. b The TetR-P39K mutant is not capable of recognizing the operators and is unable to repress the TetR-Venus expression, constituting a non-self-repression gene circuit