MORF9 increases the RNA-binding activity of PLS-type pentatricopeptide repeat protein in plastid RNA editing

• Published in: Nature plants Vol. 3; no. 5; p. 17037
• Main Authors: Yan, Junjie, Zhang, Qunxia, Guan, Zeyuan, Wang, Qiang, Li, Li, Ruan, Fengying, Lin, Rongcheng, Zou, Tingting, Yin, Ping
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 10-04-2017; Nature Publishing Group
• Subjects: 631/1647/2258/1266; 631/449/2653; 82; 82/16; 82/83; Binding; Biomedical and Life Sciences; Crystal structure; Editing; Flowering; Flowering plants; Life Sciences; Mitochondria; Molecular modelling; Plant Sciences; Plants (botany); Plastids; Post-transcription; Proteins; Ribonucleic acid; RNA; RNA editing; Uridine
• ISSN: 2055-0278; 2055-0278
• DOI: 10.1038/nplants.2017.37

RNA editing is a post-transcriptional process that modifies the genetic information on RNA molecules. In flowering plants, RNA editing usually alters cytidine to uridine in plastids and mitochondria. The PLS-type pentatricopeptide repeat (PPR) protein and the multiple organellar RNA editing factor (MORF, also known as RNA editing factor interacting protein (RIP)) are two types of key trans-acting factors involved in this process. However, how they cooperate with one another remains unclear. Here, we have characterized the interactions between a designer PLS-type PPR protein (PLS)
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PPR and MORF9, and found that RNA-binding activity of (PLS)
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PPR is drastically increased on MORF9 binding. We also determined the crystal structures of (PLS)
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PPR, MORF9 and the (PLS)
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PPR–MORF9 complex. MORF9 binding induces significant compressed conformational changes of (PLS)
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PPR, revealing the molecular mechanisms by which MORF9-bound (PLS)
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PPR has increased RNA-binding activity. Similarly, increased RNA-binding activity is observed for the natural PLS-type PPR protein, LPA66, in the presence of MORF9. These findings significantly expand our understanding of MORF function in plant organellar RNA editing.
How the two types of key trans-acting factors, PLS-type pentatricopeptide repeat protein and the multiple organellar RNA editing factor, cooperate in plant RNA editing remains unknown. A study now uses crystal structures to characterize the mechanism.