Picking a winner: new mechanistic insights into the design of effective siRNAs.

Recent work has shown that the efficacy of a small interfering RNA (siRNA) for silencing gene expression is a function of how easy it is to unwind the siRNA from the 5'-antisense end. Based on these insights, one group has designed an algorithm that substantially improves the odds of picking an effective siRNA, and two groups have shown that 'forked' or 'frayed' siRNAs, which should be easier to unwind from the 5'-antisense end, are more effective than conventional siRNAs. These strategies represent important steps towards the rational design of effective siRNAs.