HSP90 Protein Stabilizes Unloaded Argonaute Complexes and Microscopic P-bodies in Human Cells

Key components of the miRNA-mediated gene regulation pathway are localized in cytoplasmic processing bodies (P-bodies). Mounting evidence suggests that the presence of microscopic P-bodies are not always required for miRNA-mediated gene regulation. Here we have shown that geldanamycin, a well-characterized HSP90 inhibitor, abolishes P-bodies and significantly reduces Argonaute and GW182 protein levels but does not affect the miRNA level and the efficiency of miRNA-mediated gene repression; however, it significantly impairs siRNA loading and the efficacy of exogenous siRNA. Our data suggests that HSP90 protein chaperones Argonautes before binding RNA and may facilitate efficient loading of small RNA.