Improving RNA Regulator Dynamic Range with Dual Transcriptional Translational Control Mechanism

RNA regulators are emerging as powerful tools for building transcriptional cascades and logic circuits. However, the dynamic range of RNA transcriptional regulators still doesn’t match that of their protein counterparts. This can lead to propagation of incomplete repression and cause circuit leak. Here we demonstrate how transcriptional regulators can be modified to regulate both transcription and translation, increasing repression from 85% to 98% and activation from 11 fold to over 900 fold, using transcriptional termination and RBS sequestration in a single compact RNA molecule. In order to build sophisticated RNA-only circuitry, orthogonal regulators are necessary. Initial attempts to engineer multiple regulators resulted in major crosstalk. However, by engineering the antisense to be more selective, the orthogonality was greatly improved. Additionally, we show that these modified, dual control regulators can be used in transcriptional cascades to mitigate circuit leak. As synthetic biology moves beyond parts engineering to networks, we anticipate these regulators be useful for engineering sophisticated circuits.