Department of Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign, 1304 W Pennsylvania Ave, Urbana, IL, 61801, USA.
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, 600 S Mathews Ave, Urbana, IL, 61801, USA.
J Biol Eng. 2010 Feb 26;4:4. doi: 10.1186/1754-1611-4-4.
Positive feedback is a common mechanism used in the regulation of many gene circuits as it can amplify the response to inducers and also generate binary outputs and hysteresis. In the context of electrical circuit design, positive feedback is often considered in the design of amplifiers. Similar approaches, therefore, may be used for the design of amplifiers in synthetic gene circuits with applications, for example, in cell-based sensors.
We developed a modular positive feedback circuit that can function as a genetic signal amplifier, heightening the sensitivity to inducer signals as well as increasing maximum expression levels without the need for an external cofactor. The design utilizes a constitutively active, autoinducer-independent variant of the quorum-sensing regulator LuxR. We experimentally tested the ability of the positive feedback module to separately amplify the output of a one-component tetracycline sensor and a two-component aspartate sensor. In each case, the positive feedback module amplified the response to the respective inducers, both with regards to the dynamic range and sensitivity.
The advantage of our design is that the actual feedback mechanism depends only on a single gene and does not require any other modulation. Furthermore, this circuit can amplify any transcriptional signal, not just one encoded within the circuit or tuned by an external inducer. As our design is modular, it can potentially be used as a component in the design of more complex synthetic gene circuits.
正反馈是许多基因回路调节中常用的一种机制，因为它可以放大对诱导物的响应，并且还可以产生二进制输出和滞后。在电路设计的背景下，正反馈通常在放大器的设计中被考虑。因此，类似的方法可能用于合成基因回路中放大器的设计，例如在基于细胞的传感器中具有应用。
我们开发了一种模块化的正反馈电路，可作为遗传信号放大器，提高对诱导物信号的敏感性，同时增加最大表达水平，而无需外部辅助因子。该设计利用了群体感应调节剂 LuxR 的组成激活、独立于自动诱导的变体。我们通过实验测试了正反馈模块分别放大单组分四环素传感器和双组分天冬氨酸传感器输出的能力。在每种情况下，正反馈模块都放大了对各自诱导物的响应，无论是在动态范围还是灵敏度方面。
我们设计的优势在于，实际的反馈机制仅取决于单个基因，并且不需要任何其他调制。此外，该电路可以放大任何转录信号，而不仅仅是电路内编码或由外部诱导物调谐的信号。由于我们的设计是模块化的，它可以作为更复杂的合成基因回路设计的组件。
