The DYW domains of pentatricopeptide repeat RNA editing factors contribute to discriminate target and non-target editing sites

Abstract

In land plant organelles, many transcripts are modified by cytidine to uridine RNA editing. Target cytidines are specifically recognized by nuclear-encoded pentatricopeptide repeat (PPR) proteins via their sequence-specific RNAbinding motifs. In the moss Physcomitrella patens, all PPR editing factors have C-terminal E and DYW domains. To examine the contribution of E and DYW domains in RNA editing, we performed a complementation assay using mutated PpPPR-56 and PpPPR-71, which are responsible for mitochondrial editing sites. This assay showed that both E and DYW domains are required for RNA editing at the target sites, and that the conserved zinc-binding signature and the terminal triplet of the DYW domain are essential for editing. In addition, DYW domain-swapping experiments demonstrated that DYW domains are functionally different between PpPPR-56 and other mitochondrial PPR editing factors, and that residues 37-42 of the DYW domain are involved in sitespecific editing. Our results suggest that PPR-DYW proteins specifically recognize their target editing sites via PPR motifs and the DYW domain.