Module 3: Time-delay genetic circuit

In nature, a fundamental “device” in gene regulation circuits is time-delay responses to internal or external stimuli. These devices are involved in essential patterns such as oscillating systems, circadian clocks, cell differentiation and development, to mention a few [1]. Time-delay circuits have the capability to integrate signals and trigger events after a delay from the initial detection event. There are two approaches to construct a time delay genetic circuit, these are: 1) protein-based transcriptional regulators and 2) RNA-based post-transcriptional regulators [2]. In order to gain a better understanding into how certain genetic circuits are built and how they work to derive in complex responses upon stimuli, in the field of synthetic biology, the reconstruction of genetic circuits is one of the more investigated topics. Specifically, experiments focused on transcriptional regulation components are relatively well understood and easy to emulate. Although circuits based on transcriptional networks can provide complex behaviors, as the complexity increases it is clear that many natural circuits are not only transcriptional driven but they are controller in other levels such as post-transcriptional regulation [3].

Based on different literature and the requirements of the project, two genetic configurations, one protein-based and other RNA-based, have been considered as implementations of a time-delay genetic circuit.

Why?

As mentioned in the project description, one important feature of our system is the reset of the signal once the message is received. The time between when the signal (or self destructive plasmid/conjugation plasmid) has been received and the reset (or destruction of the plasmid) is an important parameter which will allow the signal to be send to the next cell (receiver) through the consecutive conjugation system before “losing” the message. Therefore, it is necessary to construct a device which will provide enough time for the two subsequent events happen. This device has been termed the time-delay genetic circuit in this project. In a final version,.... more.

How?

From the literature review, two different genetic circuit configurations were contemplated: A synthetic transcriptional cascade approach, which has been showed to perform time-delay behavior in previous studies [4] and an approach based on post-transcriptional regulation which we termed biosynthetic AND gate. As the conjugation system will have two plasmids (signal and helper plasmids), the approach.... more.

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