Silencing of HIV-1 by AgoshRNA molecules.

RNA interference (RNAi) is a sequence-specific gene silencing mechanism that is triggered by the expression of a short hairpin RNA (shRNA). shRNA molecules enter the RNAi pathway at the Dicer processing step. Recent studies indicated that the cellular microRNA miR-451 is not recognized by Dicer, but that it is processed instead by the Argonaute 2 (Ago2) protein. Subsequently, Dicer-independent shRNAs were described that rely on Ago2 for processing, as well as the subsequent silencing step. We called these AgoshRNA molecules because they depend on Ago2 both for maturation and activation. Processing of an AgoshRNA yields only a single active RNA strand, thus reducing the chance of adverse off-target effects induced by the passenger strand of regular shRNAs. In this study, we converted several anti-HIV-1 shRNAs into AgoshRNAs. Seven of the 21 designed AgoshRNAs were potent anti-HIV molecules, although their RNAi activity is generally somewhat reduced compared with the matching shRNAs. The AgoshRNA candidates revealed no cellular toxicity. This may relate to the absence of passenger strand expression, which was verified for these AgoshRNA candidates. Furthermore, we demonstrate that a toxic shRNA can be converted into a non-toxic AgoshRNA.