FIG. 2. Types of RNA therapy. (A) Antisense RNA (single-stranded RNA). The single-stranded antisense RNA is designed to bind to pre- or mature mRNA. After binding, it modulates the splicing of pre-mRNA or induces the degradation of mRNA. It can also inhibit the translation of mRNA into protein. (B) Small interfering RNA (double-stranded RNA). The small interfering RNA (siRNA) is introduced as a double-stranded form. After loading into the RNA-induced silencing complex (RISC), one strand is removed after strand separation. The siRNA-RISC complex binds to target mRNA sequence-specifically and cleaves the mRNA (depicted as scissor) inducing its degradation. (C) RNA aptamer. The RNA aptamer can bind to a specific protein and block its function. (D) Messenger RNA. After the messenger RNA (mRNA) is introduced into the cells, cellular machinery including the ribosome translates its information into a protein, the final product that can work as an enzyme or antigen.