Combining transcriptional and translational resource allocation controllers for synthetic circuits

Recent work on engineering synthetic cellular circuitry has shown that non-regulatory interactions brought about through competition for shared gene expression resources, such as RNA polymerase and ribosomes, can result in degraded performance (circuit behaviour that deviates from design specifications) or even failure (qualitatively different functionality). Transcriptional and translational resource allocation controllers based on orthogonal `circuit-specific' gene expression machineries have previously been separately designed to alleviate the impact of this resource competition, restoring modularity and improving circuit performance. Here we investigate the potential for combining transcriptional and translational controllers into one overarching resource allocation system. We show that interactions between the transcriptional and translational controllers can lead to loss of stability, and show how they may be redesigned to restore stable and robust resource allocation.