Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 119, Issue 39, Pages -Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.2210978119
Keywords
GRP23; editosome; Arabidopsis; mitochondrion; MORF
Categories
Funding
- National Natural Science Foundation of China [32072126, 31630053]
- Shandong Provincial Natural Science Foundation [ZR2019MC005]
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The GLUTAMINE-RICH PROTEIN23 (GRP23) plays an essential role in mitochondrial RNA editing by interacting with MORF proteins and atypical DYW-type PPR proteins. GRP23 is targeted to mitochondria, plastids, and nuclei. The interactions between GRP23, MORF proteins, and PPR-DYW proteins increase the stability of the editing complex and facilitate the formation of the editosome.
Identifying the PPR-E+-NUWA-DYW2 editosome improves our understanding of the C-to-U RNA editing in plant organelles. However, the mechanism of RNA editing remains to be elucidated. Here, we report that GLUTAMINE-RICH PROTEIN23 (GRP23), a previously identified nuclear transcription regulator, plays an essential role in mitochondrial RNA editing through interacting with MORF (multiple organellar RNA-editing factor) proteins and atypical DYW-type pentatricopeptide repeat (PPR) proteins. GRP23 is targeted to mitochondria, plastids, and nuclei. Analysis of the grp23 mutants rescued by embryo-specific complementation shows decreased editing efficiency at 352 sites in mitochondria and 6 sites in plastids, with a predominant specificity for sites edited by the PPR-E and PPR-DYW proteins. GRP23 interacts with atypical PPR-DYW proteins (MEF8, MEF8S, DYW2, and DYW4) and MORF proteins (MORF1 and MORF8), whereas the four PPR-DYWs interact with the two MORFs. These interactions may increase the stability of the GRP23-MORF-atypical PPR-DYW complex. Furthermore, analysis of mef8(N Delta 64aa) mef8s double mutants shows that MEF8/MEF8S are required for the editing of the PPR-E protein-targeted sites in mitochondria. GRP23 could enhance the interaction between PPR-E and MEF8/MEF8S and form a homodimer or heterodimer with NUWA. Genetic complementation analysis shows that the C-terminal domains of GRP23 and NUWA possess a similar function, probably in the interaction with the MORFs. NUWA also interacts with atypical PPR-DYWs in yeast. Both GRP23 and NUWA interact with the atypical PPR-DYWs, suggesting that the PPR-E proteins recruit MEF8/MEF8S, whereas the PPR-E+ proteins specifically recruit DYW2 as the trans deaminase, and then GRP23, NUWA, and MORFs facilitate and/or stabilize the E or E+-type editosome formation.
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