Synthetic eukaryotic promoter and mRNA. A) In the configuration here shown, a promoter is bound by a repressor R1 and an activator A1. Every operator is labeled with the name of the corresponding transcription factor and the position with respect to the TSS (the lower the integer, the closer the operator to the TSS). A star marks the operators with the highest affinity in case of cooperativity. B) mRNA with four riboswitches along the 5’-UTR (three of them are tandem ones) and two siRNA binding sites on the 3’-UTR region. The ribosome binding site is sequestered by the riboswitches nearby when they are in their inactive configuration.