Team:BrownTwo/Limiter/intro

Threshold Regulation

Threshold limitation

In the early days of radio, AM transmitters were vulnerable to overload by an input signal of too great a magnitude. To protect the transmitter from damage, a limiter circuit was employed to attenuate signal peaks while allowing all subthreshold signal to pass through unchanged. We have designed a genetic circuit that behaves similarly. Our gene network reacts to the level of transcription of a gene of interest, limiting it to levels above or below a user-defined threshold. In our proof-of-concept, we use synthetic transcription factors to limit the expression of an inducible reporter. In practice, these modular transcription factors can be used to regulate any endogenous gene with a known promoter and transcription factor DNA-binding domain. Extremes of gene expression can damage living systems, while normal expression is healthy. Our limiter could react to the level of a gene's expression within individual cells, correcting problems only where and when they occur.

An Electronic Limiter Circuit