Talk abstracts

Talk on Saturday 10:00-10:15am submitted by Hui Li

Thermodynamically stable RNA three-way junction and X-motif with unusual properties for application in nanotechnology and cancer therapy

Farzin Haque, Dan Shu (Nanobiotechnology Center, Markey Cancer Center, and Department of Pharmaceutical Sciences, University of Kentucky), Yi Shu (Nanobiotechnology Center, Markey Cancer Center, and Department of Pharmaceutical Sciences, University of Kentucky), Hui Li (Nanobiotechnology Center, Markey Cancer Center, and Department of Pharmaceutical Sciences, University of Kentucky), Piotr Rychahou (Markey Cancer Center, University of Kentucky), Mark Evers (Markey Cancer Center, University of Kentucky), Peixuan Guo (Nanobiotechnology Center, Markey Cancer Center, and Department of Pharmaceutical Sciences, University of Kentucky)

Abstract:
We discovered a phi29 pRNA three-way junction (3WJ) motif with unusual thermodynamic stability. The ΔG of the nanoparticles is extremely low and the slope of the melting temperature curve of the three-fragment RNA complex is close to 90°. The motif was used as a RNA scaffold to construct bi-, tri-, and tetra-valent RNA nanoparticles with very high chemical and thermodynamic stability (1-3). The resulting RNA nanoparticles are resistant to denaturation in 8M urea and, do not dissociate at ultra-low concentrations in vitro and in vivo. Each arm of the three-way junction (3WJ) or X-motif can harbor one siRNA, ribozyme, miRNA or aptamer without affecting the folding of the central core, and each daughter RNA molecule within the nanoparticle fold into respective authentic structure, and retain their independent function (Fig. 1). Epigenetic regulation effects progressively increased with increasing number of functional modules in the nanoparticle. More importantly, systemic injection of the ligand-containing nanoparticles into the tail-vein of mice revealed that the RNA nanoparticles remained intact without showing any sign of dissociation or degradation; and strongly bound to cancers without detectable entry into liver, lung or other organs or tissues. Pharmacokinetic analysis in mice revealed that the half-life of RNA nanoparticles was extended 10-fold compared to the siRNA counterpart, and did not induce cytokine, interferon, antibody, and toxicity while retaining favorable biodistribution and pharmacokinetics profiles.

References:
1. Shu D, Shu Y, Haque F, Abdelmawla S, Guo P. Thermodynamically stable RNA three-way junction as a platform for constructing multifunctional nanoparticles for delivery of therapeutics. Nature Nanotech. 2011; 6:658.
2. Haque F, Shu D, Shu Y, Shlyakhtenko LS, Rychahou PG, Evers BM, Guo P Ultrastable synergistic tetravalent RNA nanoparticles for targeting to cancers. Nano Today. 2012. 7:245.
3. Guo P. The emerging field of RNA nanotechnology. Nature Nanotech. 2010. 5:833.

Keywords: RNA nanoparticle, three-way junction, X-motif