Bioengineered non-coding RNA agent (BERA) in action

Abstract

Non-coding RNAs (ncRNAs) including microRNAs (miRNAs) and small interfering RNAs (siRNAs) are important players in the control of gene regulation and represent novel promising therapeutic targets or agents for the treatment of various diseases. While synthetic ncRNAs are predominately utilized, the effects of excessive artificial modifications on higher-order structures, activities and toxicities of ncRNAs remain uncertain. Inspired by recombinant protein technology allowing large-scale bioengineering of proteins for research and therapy, efforts have been made to develop practical and effective means to bioengineer ncRNA agents. The fermentation-based approaches shall offer biological ncRNA agents with natural modifications and proper folding critical for ncRNA structure, function and safety. In this article, we will summarize current recombinant RNA platforms to the production of ncRNA agents including siRNAs and miRNAs. The applications of bioengineered ncRNA agents for basic research and potential therapeutics are also discussed.

Keywords: bioengineering; cancer; miRNA; non-coding RNAs; siRNA; therapy.

Figure 1.

The mechanistic actions of siRNA and miRNA derived from genome. siRNA: Dicer processes dsRNA (either transcribed or artificially introduced) into siRNA, which is then loaded into the RISC. AGO2, a component of RISC, cleaves the passenger strand of siRNA. The guide strand guides the active RISC to the target mRNA and binds to the target mRNA completely, leading to the cleavage of mRNA. miRNA: miRNA gene is transcribed by RNA polymerase II in the nucleus to pri-miRNA, which is then cleaved by Drosha to form pre-miRNA. The pre-miRNA is transported by Exportin-5 to the cytoplasm and then processed by Dicer to miRNA, which is loaded into the RISC. The passenger strand is removed and the remaining strand guides the RISC to the target mRNA through partially complementary binding to the miRNA response elements within 3'UTR, leading to translational repression, degradation or cleavage of the target mRNA.

Figure 2.

Bioengineering of ncRNA agents for research and therapy. The sequence of target ncRNA is cloned into a target vector. Overexpression of target ncRNA is verified and then purified from total RNAs. Bioengineered ncRNA is subjected to structural characterization, and then used for in vitro and in vivo studies before clinical investigations.