Control of ADAR2 Dimerization and RNA Editing Efficiency by Site-Specific 2'-Fluoro Modification of Guide RNAs.

Adenosine Deaminases Acting on RNA (ADARs) are an important class of RNA editing enzymes that catalyze the deamination of adenosine (A) to inosine (I) in double-stranded RNA (dsRNA). Since inosine is typically read as guanosine (G) during translation, ADARs can produce A to G transitions in dsRNA. Site-directed RNA editing (SDRE) is a promising therapeutic tool wherein guide RNAs can be used to direct endogenous human ADARs to reverse disease-causing mutations in specific RNA transcripts. Guide RNA (gRNA) modifications at locations that contact the ADAR active site are often used to improve editing efficiency. However, little is known about rate-enhancing chemical modifications in the gRNA at the dsRNA binding domain (dsRBD)-RNA interface. Analysis of published crystal structures of ADAR2 bound to dsRNA suggested positions at this interface would be sensitive to gRNA modification. In this work, gRNAs bearing 2'-modifications in the dsRBD binding site were synthesized and subsequently tested to determine their effects on the editing rate of therapeutically relevant ADAR targets. We found that replacing a single 2'-OH at specific positions on the gRNA with a 2'-F substantially increased the rate of