Zehrmann Anja, Verbitskiy Daniil, van der Merwe Johannes A, Brennicke Axel, Takenaka Mizuki
Molekulare Botanik, Universität Ulm, 89069 Ulm, Germany.
Plant Cell. 2009 Feb;21(2):558-67. doi: 10.1105/tpc.108.064535. Epub 2009 Feb 27.
RNA editing in flowering plant mitochondria alters 400 to 500 nucleotides from C to U, changing the information content of most mRNAs and some tRNAs. So far, none of the specific or general factors responsible for RNA editing in plant mitochondria have been identified. Here, we characterize a nuclear-encoded gene that is involved in RNA editing of three specific sites in different mitochondrial mRNAs in Arabidopsis thaliana, editing sites rps4-956, nad7-963, and nad2-1160. The encoded protein MITOCHONDRIAL RNA EDITING FACTOR1 (MEF1) belongs to the DYW subfamily of pentatricopeptide repeat proteins. Amino acid identities altered in MEF1 from ecotype C24, in comparison to Columbia, lower the activity at these editing sites; single amino acid changes in mutant plants inactivate RNA editing. These variations most likely modify the affinity of the editing factor to the affected editing sites in C24 and in the mutant plants. Since lowered and even absent RNA editing is tolerated at these sites, the amino acid changes may be silent for the respective protein functions. Possibly more than these three identified editing sites are addressed by this first factor identified for RNA editing in plant mitochondria.
开花植物线粒体中的RNA编辑会使400到500个核苷酸由C变为U，从而改变大多数mRNA和一些tRNA的信息内容。到目前为止，尚未鉴定出植物线粒体中负责RNA编辑的任何特异性或一般性因子。在此，我们对拟南芥中一个核编码基因进行了表征，该基因参与不同线粒体mRNA中三个特定位点的RNA编辑，即编辑位点rps4-956、nad7-963和nad2-1160。编码的蛋白质线粒体RNA编辑因子1（MEF1）属于五肽重复蛋白的DYW亚家族。与哥伦比亚生态型相比，生态型C24的MEF1中氨基酸同一性的改变降低了这些编辑位点的活性；突变植物中的单氨基酸变化使RNA编辑失活。这些变异很可能改变了编辑因子对C24和突变植物中受影响编辑位点的亲和力。由于这些位点可以耐受降低甚至缺失的RNA编辑，氨基酸变化可能对各自的蛋白质功能没有影响。可能有超过这三个已鉴定的编辑位点由这个首次鉴定出的植物线粒体RNA编辑因子负责。
