Difference between revisions of "Part:BBa K1062000"

Latest revision as of 19:37, 27 September 2013

Guide RNA (gRNA) target for RFP

This part is a guide RNA (gRNA) that targets the RFP gene, when bound to Cas9. It also contains a cleavage site recognized by the Csy4 enzyme which allows it to be cleaved from neighboring DNA/RNA.

Sequence and Features

Usage and Biology

In both of our projects, we used gRNAs and dCas9 as:

1) To specifically target and repress the "virulence gene" (we used flourescent proteins as a proof of concept) in our conjugation project

2) Improve past circuits with better decision making by using dCas9 instead of traditional repressors.

Characterization

We validated that this part works by testing it in our designed CRISPRi system. The RFP guideRNA (RFPi or RFP-gRNA) was transformed into a strain of JM109 containing RFP in its genome. The RFPi was on a plasmid also containing dCAS9 the protein necessary for targeting to and repression of the RFP.

The efficiency of CRISPRi system measured by directly transform conjugative plasmid that contains CRISPRi system (sgRNA and dCas9 protein) for RFP into JM109 strain that have RFP inserted into its chromosome. The dCas9 protein of the repression system was under control of a pTET promoter and the sgRNA of the system was under control of a constitutively expressed promoter. Positive control was directly transform of conjugative plasmid backbone (pARO190 without sgRNA and dCas9) into JM109 strain that have RFP inserted into its chromosome, and negative control was directly transform of conjugative plasmid that contains CRISPR/Cas repression system (sgRNA and dCas9 protein) for RFP into JM109 strain without any fluorescent markers. RFP level were measured by flow cytometry and error bars showed standard deviation calculated on the basis of technical replicates.

Conjugation Project

In the Conjugation Project, our target contained a RFP cassette that is knocked into the chromosome of the strain. Due to the fact that the target strain is essential to proving the Conjugation Project, this gRNA is essential in order to prove that repression of a specific target can be possible.

Synthetic Circuit

In the Synthetic Circuit, the target is the RFP gene that would be located in the High Concentration Pathway. The purpose of the gRNA is to prevent any possibility of the RFP gene expressing, due to a possible leaky promoter, when the Low Concentration Pathway is being induced.