We have created a part collection that can build up an RNA sensing system. The genetic device for sensing is mainly composed of three kinds of parts: the regulatory part, the coding part, and essential genetic elements.
Regulatory part: toehold switch
A toehold switch is a secondary structure RNA with a hairpin loop that can be used to regulate the translation of downstream proteins. Upon binding with specific RNA, the stem-loop structure will be unwound, triggering the expression of the downstream reporter. Our team has designed 21 new parts that can detect miR-21, miR-31and miR-146. We thoroughly characterized each of them in the part registry, in the hopes that they can be easily used by other teams.
Coding part: reporter
There are 2 reporters in our collection. Different reporters are suitable in different situations.
Essential genetic elements: promoter and terminator
- Invertase: It can convert sucrose into glucose, which can be easily measured by a personal glucose meter (PGM). The detection with the invertase can be applied in clinics or homes, as the measurement process is easy to carry out, and does not require expensive equipment.
- sfGFP: It can emit green fluorescence, which can be measured with the plate reader or a spectrometer. The detection with sfGFP is especially suitable for the laboratory. With all the required devices, the measurement can be efficient in detecting a large number of samples.
T7 promoter and T7 terminator are the existing parts in iGEM. With them, the plasmid can be in vitro transcribed and translated with the PURExpress protein synthesis kit, making it more useful for detection.
RNA sensing system
Our project seems to only focus on oral cancer detection, however, the collection can build up a framework for an RNA sensing system. It can be further used in other detection of RNAs, such as oncogenic miRNAs in the blood sample or RNA virus like coronavirus or zika virus. With our part collection and comprehensive introduction of the toehold switch design, other teams can apply the genetic devices in different situations.