Nat. Biotechnol. 37, 1209–1216 (2019).

Engineered chemical control of cellular response is currently limited to low complexity, single-input/single-output approaches. Foight et al. describe a synthetic post-translational control system where a central receiver protein, NS3a protease in their case, is targeted by multiple clinically approved drugs. ‘Reader’ proteins are computationally designed to specifically recognize the drug (danoprevir or grazoprevir)-bound forms of NS3a, and to colocalize to different parts of the cell. Evaluation of the multi-input/multi-output behavior in mammalian cells shows that these reader proteins maintain specificity to the target states of NS3a in mammalian cell cultures, and provide a programmable transcriptional control when either drug is used. The system is also able to achieve proportional and graded control when using different proportions of the two drugs and corresponding reader proteins. The method, termed pleiotropic response outputs from a chemically inducible single receiver (PROCISiR), could be useful for programming in vitro and in vivo cellular control.