Principles of cell-free genetic circuit assembly

TLDR

The study aims to engineer transcriptional activation and repression cascades where each protein product serves as the input for the next stage. The authors constructed these genetic circuit elements in a cell‑free transcription–translation extract, enabling rapid assembly of cascades. They found that while single stages can operate linearly, cascading stages forces nonlinear behavior, leading to cumulative time delays and output reductions due to a translation bottleneck, which can be alleviated by accelerating RNA turnover to reduce competition and stabilize output.

Abstract

Cell-free genetic circuit elements were constructed in a transcription–translation extract. We engineered transcriptional activation and repression cascades, in which the protein product of each stage is the input required to drive or block the following stage. Although we can find regions of linear response for single stages, cascading to subsequent stages requires working in nonlinear regimes. Substantial time delays and dramatic decreases in output production are incurred with each additional stage because of a bottleneck at the translation machinery. Faster turnover of RNA message can relieve competition between genes and stabilize output against variations in input and parameters.