(760h) Role of TRBP and PACT in Asymmetry Sensing

Short interfering RNAs (siRNAs) were recognized for their potential as therapeutics soon after their discovery as a method of targeted gene knockdown using the endogenous RNA interference (RNAi) pathway. Mimicking the natural structure of endogenous miRNAs and siRNAs, siRNAs should have 19bp with 2nt 3’ overhangs. siRNAs are designed to be fully complementary with their target RNA; still, sequence selection is not necessarily straightforward. This is due to the number of critical inter- and intramolecular interactions that determine the eventual activity of the siRNA in silencing its target. Prominent among these are the interactions of the siRNA with the RNAi pathway proteins that result in the selection of one strand as the guide strand and the subsequent destruction of the complementary passenger strand. The preferential selection of one strand is referred to as asymmetry, and the asymmetry information is contained in the sequence of the siRNA. Thus, an understanding of the mechanism of achieving asymmetry is essential for siRNA design.

Our work focuses on defining characteristics of an effective siRNA, in this case identifying the siRNA characteristics that result in preferential selection of one siRNA strand over the other. siRNA strand selection is believed to occur in a ribonucleoprotein complex that forms before the active complex, called the RNA Induced Silencing Complex (RISC) Loading Complex (RLC). Strand selection then occurs based upon directional binding of the siRNA by the RLC. In this presentation, we will describe our work investigating the roles of various RLC and related proteins on determining siRNA asymmetry and how asymmetry defines eventual silencing efficiency of these siRNAs.