Despite considerable interest and investigations on cationic lipid-DNA complexes, reports on lipid-RNA interaction are very limited. In contrast to lipid-DNA complexes where lipid binding induces partial B to A and B to C conformational changes (1), lipid-tRNA complexation preserves tRNA folded state. This study is the first attempt to investigate the binding of cationic lipid with transfer RNA and the effect of lipid complexation on tRNA aggregation and condensation. We examine the interaction of tRNA with cholesterol (Chol), 1,2-dioleoyl-3-trimethylammonium-propane(DOTAP),dioctadecyldimethylammoniumbromide(DDAB), and dioleoylphosphatidylethanolamine (DOPE), at physiological condition, using constant tRNA concentration and various lipid contents. FTIR, UV-Visible, CD spectroscopic methods and atomic force microscopy (AFM) were used to analyse lipid binding site, the binding constant and the effects of lipid interaction on tRNA stability, conformation and condensation. Structural analysis showed lipid-tRNA interactions with G-C and A-U base pairs as well as the backbone phosphate group with overall binding constants of K_Chol= 5.94 (±0.8) x 10⁴M^-1, K_DDAB= 8.33 (±0.90) x 10⁵M^-1, K_DOTAP=1.2 (±0.30) x 10⁵M^-1, and K_DOPE=2.75 (± 0.50) x 10⁴M^-1. The order of stability of lipid-tRNA complexation is DDAB>DOTAP>Chol>DOPE. Hydrophobic interactions between lipid aliphatic tails and tRNA were observed. RNA remains in A-family structure, while biopolymer aggregation and condensation occurred at high lipid concentrations.

The AFM images below show the condensation of tRNA by several lipids for the first time.




References and Notes

1. Marty, R., N? soukpoe-Kossi, C. N., Charbonneau, D., Weinert, C. M. Kreplak, L. and Tajmir-Riahi, H. A. Structural analysis of DNA complexation with cationic lipids. Nucl. Acids Res. 37, 749-757 (2009).