Design of Nuclease-Resistant Fork-Like Small Interfering RNA (fsiRNA)

Small interfering RNAs (siRNAs) are potent inducers of RNA interference—the conservative cellular process of posttranscriptional gene silencing. The silencing activity of siRNAs depends on the thermodynamic asymmetry of the siRNA duplex. Here, we describe the design of chemically modified fork-like siRNA (fsiRNAs) containing mismatches at the 3′-end region of the sense strand and 2′-O-methyl modifications in nuclease-sensitive sites, capable of silencing of thermodynamically unfavorable targets.