The effect of cationic liposome prepared from 1,2-dioleoyl-3-trimethyl- ammonium-propane (DOTAP) on the gene expression at the mRNA translation level was investigated using an E. coli cell-free translation system. DOTAP liposome at 3 mM inhibited the mRNA translation of green fluorescent protein (GFP), as indicated both by the fluorescence intensity of GFP and by SDS-PAGE analysis. The role of DOTAP liposome on the inhibition of mRNA translation was revealed that the cationic quaternary amine groups on the liposome surface can interact and neutralize the anionic phosphate groups on mRNA by an electrostatic interaction. mRNA molecules still existed without any degradation in the presence of DOTAP liposome although it could not be translated. These results clearly illustrated that the DOTAP liposome could knock down mRNA and silence its activity of translation in an E. coli cell-free system. (C) 2010 Elsevier B.V. All rights reserved.