Trans and cis factors affecting A-to-I RNA editing efficiency of a noncoding editing target in C. elegans

Adenosine-to-inosine RNA editing by ADARs affects thousands of adenosines in an organism's transcriptome. However, adenosines are not edited at equal levels nor do these editing levels correlate well with ADAR expression levels. Therefore, additional mechanisms are utilized by the cell to dictate the editing efficiency at a given adenosine. To examine cis- and trans-acting factors that regulate A-to-I editing levels specifically in neural cells, we utilized the model organism Caenorhabditis elegans. We demonstrate that a double-stranded RNA (dsRNA) binding protein, ADR-1, inhibits editing in neurons, which is largely masked when examining editing levels from whole animals. Furthermore, expression of ADR-1 and mRNA expression of the editing target can act synergistically to regulate editing efficiency. In addition, we identify a dsRNA region within the Y75B8A.8 3′ UTR that acts as a cis-regulatory element by enhancing ADR-2 editing efficiency. Together, this work identifies mechanisms that regulate editing efficiency of noncoding A-to-I editing sites, which comprise the largest class of ADAR targets.