Reversible control of gene expression by guest-modified adenosines in a cell-free system via host–guest interaction

Gene expression technology has become an indispensable tool for elucidating biological processes and developing bio-technology. Cell-free gene expression (CFE) systems offer a fundamental platform for gene expression-based technology, in which the reversible and programmable control of transcription can expand its use in synthetic biology and medicine. This study shows that CFE can be controlled via the host–guest interaction of cucurbit[7]uril (CB[7]) with N6-guest-modified adenosines. These adenosine derivatives were conveniently incorporated into the DNA strand by a post-synthetic approach and formed a selective and stable base pair with complementary thymidine in DNA. Meanwhile, alternate addition of CB[7] and the exchanging guest molecule induced the reversible formation of a duplex structure through the formation and dissociation of a bulky complex on DNA. The kinetics of the reversibility were fine-tuned by changing the size of the modified guest moieties. When incorporated into a specific region of the T7 promoter sequence, the guest-modified adenosines enabled the tight and reversible control of in vitro transcription and protein expression in the CFE system. The present study marks the first utility of the host-guest interaction for the gene expression control in the CFE system, opening new avenues for developing DNA-based technology, particularly for precise gene therapy and DNA nano-technology.