Abstract
Terminators, signaling the end of transcription process, are usually placed behind the last coding sequence of an operon to prevent interference between transcript units in most biologically synthetic systems. In this study, we seek to extend the usability of terminators in genetic system design by using terminators as regulatory genetic parts. Terminators with different impacts on their upstream and downstream genes are characterized in details via dynamic modeling to predict the behavior of the overall genetic system. Some nonlinear effects of terminators were observed in our terminator measurements. This potentially provides versatile regulation on gene expression. The genetic systems designed with regulatory terminators are predicted to behave like genetic filters through dynamic modeling in silico. In agreement with the simulations, genetic highpass and bandpass filters are successfully implemented in vitro, which demonstrates the potential of using terminators as regulatory parts. The genetic bandpass filter in this work is implemented through the interdependence between genetic parts, where the termination efficiency of terminator varies with the strength of upstream promoter. This design strategy of bandpass filter requires fewer base pairs than the conventional strategy of concatenating a highpass and lowpass filter. Our results show that novel utilization of terminators as regulatory parts can provide us a new perspective for efficient genetic circuit design. To move towards this direction, we believe that further exploration of the complicated dynamics of terminators is important for future advance in the development of synthetic biology.