A gene expression control technology for cell-free systems and synthetic cells via targeted gene silencing and transfection.

Synthetic cells, expressing proteins using cell-free transcription-translation (TXTL), is a technology utilized for a variety of applications, such as investigating natural gene pathways, metabolic engineering, drug development or bioinformatics. For all these purposes, the ability to precisely control gene expression is essential. Various strategies to control gene expression in TXTL have been developed; however, further advancements on gene-specific and straightforward regulation methods are still needed. Here, we present a method of control of gene expression in TXTL using a "silencing oligo": a short oligonucleotide, designed with a particular secondary structure, that binds to the target messenger RNA. We demonstrated that silencing oligo inhibits protein expression in TXTL in a sequence-dependent manner. We showed that silencing oligo activity is associated with RNase H activity in bacterial TXTL. To complete the gene expression control toolbox for synthetic cells, we also engineered a first transfection system. We demonstrated the transfection of various payloads, enabling the introduction of RNA and DNA of different lengths to synthetic cell liposomes. Finally, we combined the silencing oligo and the transfection technologies, demonstrating control of gene expression by transfecting silencing oligo into synthetic minimal cells.

Expanding luciferase reporter systems for cell-free protein expression.

Luciferases are often used as a sensitive, versatile reporter in cell-free transcription-translation (TXTL) systems, for research and practical applications such as engineering genetic parts, validating genetic circuits, and biosensor outputs. Currently, only two luciferases (Firefly and Renilla) are commonly used without substrate cross-talk. Here we demonstrate the expansion of the cell-free luciferase reporter system, with two orthogonal luciferase reporters: N. nambi luciferase (Luz) and LuxAB. These luciferases do not have cross-reactivity with the Firefly and Renilla substrates. We also demonstrate a substrate regeneration pathway for one of the new luciferases, enabling long-term time courses of protein expression monitoring in the cell-free system. Furthermore, we reduced the number of genes required in TXTL expression, by engineering a cell extract containing part of the luciferase enzymes. Our findings lead to an expanded platform with multiple orthogonal luminescence translation readouts for in vitro protein expression.