Figure 5.

Trigger-dependent siRNA formation. (A) Activable siRNA probe. The first proposed technology for activation of the siRNA therapeutic function by an RNA trigger. In the initial stage, the sense strand is disactivated by forming a hairpin structure that can be opened by the trigger strand with subsequent binding to the antisense strand. The activated complex is than processed by Dicer with the yield of an active functional siRNA molecule ¹²¹. (B) Modified oligonucleotide-inducible RNAi (MONi RNAi). Double hairpin structure expressed from a plasmid contains two stem-loops: (1) MON sensor that recognizes a small chemically modified oligonucleotide (MON) trigger, and (2) RNAi effector domain. After recognizing the MON trigger, MON sensor opens and makes the RNAi effector domain available for further processing by Drosha and Dicer with the yield of a functional siRNA molecule ¹²².