Specific delivery of therapeutic RNAs using bacteriophage phi29 pRNA as a vector

Songchuan Guo, Purdue University

Abstract

The clinical applications of small therapeutic RNAs including siRNA and ribozyme have been hindered by the lack of an efficient and safe delivery system that targets specific cells. In this study, packaging RNA (pRNA), a critical component of the DNA-packaging motor of bacteriophage phi29, was engineered by RNA nanotechnology to construct chimeric pRNA that contains gene silencing moiety (siRNA or ribozyme) or cell recognition moiety (folate or RNA aptamer). Chimeric pRNAs with inserted moieties retain the properties of forming dimers or trimers via interlocking interaction between the right- and left-hand loops. Incubation of cancer cells with a pRNA dimer, in which one subunit harbors folate as a cancer recognition moiety and the other contains siRNA against anti-apoptotic gene survivin, resulted in the binding and entry of this RNA dimer into the cancer cells and subsequent gene silencing. The chimeric pRNA/siRNA can be processed by Dicer and release double-stranded siRNA duplex to silence the target gene via the mechanism of RNA interference. The specific recognition of cancer cells and the anti-tumor activity of the pRNA dimer were further confirmed by ex vivo delivery in animal trials. In a trimeric pRNA complex, RNA aptamer against CD4 receptor mediated the binding and co-entry of the trivalent therapeutic particles into cells expressing CD4, and subsequently modulated the apoptosis of leukemia lymphocytes. The assembly of protein-free 25-nanometer RNA nanoparticles would allow for repeated long-term administration and avoid the problems of short retention time of small molecules and the difficulties in the delivery of particles larger than 100 nanometer.

Degree

Ph.D.

Advisors

Guo, Purdue University.

Subject Area

Molecular biology|Virology

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