A direct role for Hsp90 in pre-RISC formation in Drosophila.

Heat-shock proteins (Hsps) are molecular chaperones that control protein folding and function. Argonaute 2 (Ago2), the effector in RNA interference (RNAi), is associated with Hsp90; however, its function in RNAi remains elusive. Here we show that Hsp90 is required for Ago2 to receive the small interfering RNA (siRNA) duplex from the RNA-induced silencing complex-loading complex in RNAi, suggesting a model where Hsp90 modifies Ago2 conformation to accommodate the siRNA duplex.