Increased potency and longevity of gene silencing using validated Dicer substrates.

Chemically synthesized small interfering RNAs (siRNAs) are tools used for silencing the expression of a single gene. They are mainly employed in basic research applications, but may also have great potential in therapeutic applications. Longer double-stranded RNAs, such as Dicer-substrate 27mers, trigger gene silencing through the intrinsic RNAi pathway. The design of these Dicer-substrate 27mers has been optimized so they can be oriented by Dicer to consistently select the antisense (guide) strand after cleavage to shorter siRNAs, leading to predictable mRNA cleavage. In this paper we describe evidence that these Dicer-substrate 27mers produce more potent and sustained gene silencing for four genes when compared with synthetic 21mers that have the same guide-strand sequence. Furthermore, improved silencing by these 27mers is often more pronounced at lower concentrations.