For this year’s iGEM competition, our team has chosen to present STAR (Small Transcriptional-Activating RNA) for the award of the basic part (BBa_K1893013). STAR is a novel and entirely synthetic technology that can be used for implementing RNA logic in bacterial cells (Chappell et al, 2015). Our team is very excited to be the first to introduce a transcriptional-activator RNA technology to the iGEM competition, and make its associated library of tools available to future iGEM teams to implement in their designs.
Figure 1: A schematic representation of the STAR part (STAR-t500) in action.
For the implementation of this technology, a terminator is added immediately upstream of the gene of interest.
- In the absence of STAR, the terminator structure prevents expression of the gene of interest very robustly.
- In the presence of STAR, the STAR molecules can act in trans and base pair to a section of the terminator RNA sequence. This causes structural rearrangements that negate the function of the terminator element and allows transcription of the downstream gene of interest.
Our STAR approach offers significant advantages over traditional protein-based regulatory systems. These include:
→ Low metabolic burden: the RNA is functional after transcription, avoiding the resource-intensive translation steps.
→ Portability: trans-acting RNA based regulation is found throughout the bacterial kingdom (as well as other kingdoms) and is not host-specific.
→ Tight Regulation: In the absence of STAR there is very low baseline expression of the downstream gene, while in the presence of STAR the expression is activated 96-fold.
→ Ease of design: Watson-Crick base pairing avoids the need for structural protein-protein interactions, which are difficult to predict and design.
→ Reduced lag in circuits: RNA degradation is rapid, reducing the lag in the comparison function, and offering short time response for our comparator circuit.
Please visit our Results page: Comparator module to check out the thorough characterisation of the STAR element.
Alternatively check out STAR element (BBa_K1893013) webpage on the Registry of Standard Biological Parts website.
1. Chappell, J., Takahashi, M. & Lucks, J. (2015) Creating small transcription activating RNAs. Nature Chemical Biology. [Online] 11 (3), 214-220. Available from: doi:10.1038/nchembio.1737.