MicroRNA-regulated viral vectors for gene therapy

Figure 4 Schematic of the miR-ON system using lentiviral vectors in the indicated conditions. Two independent lentiviral vectors containing a repressor protein and a GFP reporter with operator sequences for the repressor protein, respectively. The repressor protein, either tetracycline repressor (tTR) or tTR-Kruppel-associated box, constitutively binds to the tetO sequence, thereby suppressing reporter gene expression. If the repressor mRNA containing miR-TS is not translated into native protein due to microRNA-mediated degradation of the repressor mRNA or is unable to bind tetO sequence because of doxycycline-induced allosteric changes of the repressor, GFP expression is switched on. GFP expression is inhibited if the repressor is translated due to lack of an inhibiting microRNA, thereby allowing the repressor to bind to the operator sequence. Arrows indicate orientation of transcription. Modified according to[178]. LTR: Long terminal repeats; miR-TS: Artificial microRNA target sites; pA: Polyadenylation site; tetO7: Seven tandemly arranged tetracycline operator sequences; GFP: Green fluorescent protein.