Team:Hong Kong HKUST/riboregulator

Background

Regulatory RNAs are small RNA that regulate biological processes such as transcription or translation. The use of regulatory RNAs has been a great interest in the field of synthetic biology because it provides an additional level of regulation for biological circuits and systems. Regulatory RNAs have also been used by many iGEM teams. We have identified 7 teams that have used cis-repressing (CR) and trans-activating (TA) riboregulator system and more teams that have used riboswitches. For example, Isaacs 2005, UC Berkeley 2006 and Caltech 2007 contributed many CR and TA devices to the Registry.

Although there is a significant number of regulatory RNAs available in the registry (more than 100 BioBrick parts related to regulatory RNA), comprehensive characterization information that the iGEM community can use to compare and contrast different regulatory RNAs (especially CR-TA riboregulators) is missing. For example, if we want to use the CR and TA devices that Berkeley 2006 made, we would not know which one to use and whether the device would work because it is hard to find characterization information in their wiki.

This may hinder the reliable use of regulatory RNAs. The main focus of this project is, therefore, to provide characterization information of regulatory RNAs so that teams and labs will be confident in using these devices. There are many regulatory RNAs, but since the time during the summer is limited, we have decided to focus on one type of regulatory RNAs which is the CR-TA riboregulator system.

CR and TA riboregulator system
Artificial cis-repressing and trans-activating riboregulator system was introduced to the iGEM community by Isaacs in 2005. The riboregulator system as a whole acts to regulate translation at the RNA level. One component of the system ,crRNA, which contains a cis-repressing sequence at the 5' of the RBS, RBS, and gene of interest.

The cis-repressing sequence can form a loop form complementary base pairs with the RBS to prevent the recognition of RBS by ribosomes. The translation crRNA is also commonly described as a "lock" because it "locks" the RBS and prevent translation. The "key" to this system is the taRNA. taRNA can interact (in trans) with the cis-repressing sequence to unlock the RBS and therefore activate translation (Figure 1.).

The benefits of this system, as described in Isaacs et al.'s paper, are leakage minimization, fast response time, tunability, independent regulation of multiple genes etc.