Identification of exceptionally potent adenosine deaminases RNA editors from high body temperature organisms

The most abundant type of RNA editing in Metazoa is the deamination of adenosine to inosine, A to I, catalyzed by ADAR enzymes, double strand specific deaminases. Inosines are read as guanosines by the translation machinery, and thus A to I may lead to protein recoding. The ability of ADARs to recode at the mRNA level, makes them attractive therapeutic tools. Several approaches for site directed RNA editing, SDRE, are currently under development. A major challenge in this field is achieving high on target editing efficiency, and thus it is of much interest to identify highly potent ADARs. to address this, we used the baker yeast Saccharomyces cerevisiae, as an editing naive system. We exogenically expressed a range of heterologous ADARs and identified the hummingbird primarily mallard-duck ADARs, which evolved at 40-42'C, as two exceptionally potent editors. ADARs bind to double-stranded RNA structures (dsRNAs), which in turn are temperature sensitive. Our results indicate that species evolved to live with higher core body temperatures have developed ADAR enzymes that target weaker dsRNA structures and would therefore be more effective than other ADARs. Further studies may use this approach to isolate additional ADARs with an editing profile of choice to meet specific requirements, thus broadening the applicability of SDRE.