Engineering synthetic CopT/A-based genetic circuits for miRNA imaging and functional gene regulation

Synthetic genetic circuits that can operate at the transcriptional and translation levels have been widely applied in the control of cellular behaviors and functions. However, the regulation of genetic circuits is often accompanied by the introduction of exogenous substances or the endogenous generation of inhibitory products, which would bring uncontrollable hazards for biological safety and reduce the efficiency of the system. Here, we described a miRNA-responsive CopT-CopA (miCop) genetic circuit system to realize real-time monitoring the intracellular expression of miRNA-124a during neurogenesis or miRNA-122 under the stimulation of extracellular drugs in living cells and animals. Furthermore, to prove the modularity of the system, we engineered this mipCop to tune the expression of DTA (diphtheria toxin A) gene, and showed the powerful capacity of killing cancer cells by inducing apoptosis and cell cycle arrest based on miRNA response. This study provides an effective means to couple miRNA sensing with miRNA-responsive gene modulation, which may open up new diagnostic or therapeutic applications.