Restoration of G to A mutated transcripts using the MS2-ADAR1 system.

Site-directed RNA editing (SDRE) holds significant promise for treating genetic disorders resulting from point mutations. Gene therapy, for common genetic illnesses is becoming more popular and, although viable treatments for genetic disorders are scarce, stop codon mutation-related conditions may benefit from gene editing. Effective SDRE generally depends on introducing many guideRNA molecules relative to the target gene; however, large ratios cannot be achieved in the context of gene therapy applications. Gene-encoded information can be altered, and functionally diverse proteins produced from a single gene by restoration of point-mutated RNA molecules using SDRE. Adenosine deaminase acting on RNA (ADAR) is an RNA-editing enzyme, that can specifically convert adenosine (A) residues to inosines (I), which are translated as guanosine (G). MS2 system along with ADAR1 deaminase domain can target a particular A and repair G to A mutations. In this study, we used the RNA binding MS2 coat protein fused with the ADAR1 deaminase domain controlled by the CMV promoter, and a 19 bp guide RNA (complementary to the target mRNA sequence) engineered with 6 × MS2 stem-loops downstream or 1 × MS2 stem-loop (double MS2) on either side, controlled by the U6 promoter. When the EGFP TGG codon (tryptophan) was altered to an amber (TAG), opal (TGA), or ochre (TAA) stop codon, the modified ADAR1 deaminase domain could convert A-to-I (G) at the edited sites. It is anticipated that successful establishment of this technique will result in a new era in gene therapy, allowing remarkably efficient gene repair, even in vivo.