Dynamic Control of Gene Expression with Riboregulated Switchable Feedback Promoters

One
major challenge in synthetic biology is the deleterious impacts
of cellular stress caused by expression of heterologous pathways,
sensors, and circuits. Feedback control and dynamic regulation are
broadly proposed strategies to mitigate this cellular stress by optimizing
gene expression levels temporally and in response to biological cues.
While a variety of approaches for feedback implementation exist, they
are often complex and cannot be easily manipulated. Here, we report
a strategy that uses RNA transcriptional regulators to integrate additional
layers of control over the output of natural and engineered feedback
responsive circuits. Called riboregulated switchable feedback promoters
(rSFPs), these gene expression cassettes can be modularly activated
using multiple mechanisms, from manual induction to autonomous quorum
sensing, allowing control over the timing, magnitude, and autonomy
of expression. We develop rSFPs in Escherichia coli to regulate multiple feedback networks and apply them to control
the output of two metabolic pathways. We envision that rSFPs will
become a valuable tool for flexible and dynamic control of gene expression
in metabolic engineering, biological therapeutic production, and many
other applications.