Adding the right microRNA to the correct UTR - cells survive the Ctx screen

The miR-Selection lentivector's cytotoxic sensor (Ctx) will kill the cells if either no microRNA or the incorrect microRNA is added to downregulate the Ctx gene. The VEGF Fire-Ctx UTR clone without any microRNA added does not survive the Ctx screen, but when miR-20b is added, the cells survive (Panel A.). We tested seven separate UTR clones with either no microRNA added (blue bars) or adding the known microRNA that binds to that UTR (red bars). Only when the right microRNA is added are cells able to survive the Ctx screen (Panel B. and see Table inset for which microRNA was added to which UTR clone). The corresponding luciferase reporter data for each of the UTR clones is shown in Panel C. Down regulation of the luciferase reporter can be easily measured to monitor microRNA binding activities.