Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
Department of Chemistry and Biochemistry, California State University Los Angeles, Los Angeles, CA 90032, USA.
Nucleic Acids Res. 2021 Apr 6;49(6):3490-3506. doi: 10.1093/nar/gkab066.
The RanBP2 zinc finger (Znf) domain is a prevalent domain that mediates protein interaction and RNA binding. In Arabidopsis, a clade of four RanBP2 Znf-containing proteins, named the Organelle Zinc (OZ) finger family, are known or predicted to be targeted to either the mitochondria or the plastids. Previously we reported that OZ1 is absolutely required for the editing of 14 sites in chloroplasts. We now have investigated the function of OZ2, whose null mutation is embryo lethal. We rescued the null mutant by expressing wild-type OZ2 under the control of the seed-specific ABSCISIC ACID-INSENSITIVE3 (ABI3) promoter. Rescued mutant plants exhibit severely delayed development and a distinctive morphological phenotype. Genetic and biochemical analyses demonstrated that OZ2 promotes the splicing of transcripts of several mitochondrial nad genes and rps3. The splicing defect of nad transcripts results in the destabilization of complex I, which in turn affects the respiratory ability of oz2 mutants, turning on the alternative respiratory pathway, and impacting the plant development. Protein-protein interaction assays demonstrated binding of OZ2 to several known mitochondrial splicing factors targeting the same splicing events. These findings extend the known functional repertoire of the RanBP2 zinc finger domain in nuclear splicing to include plant organelle splicing.
RanBP2 锌指（Znf）结构域是一种普遍存在的结构域，介导蛋白质相互作用和 RNA 结合。在拟南芥中，有一组四个 RanBP2 Znf 结构域的蛋白质，称为细胞器锌指（OZ）家族，已知或预测它们靶向线粒体或质体。之前我们报道过 OZ1 绝对需要叶绿体中 14 个位点的编辑。现在我们已经研究了 OZ2 的功能，OZ2 的缺失突变是胚胎致死的。我们通过在种子特异性的脱落酸不敏感 3（ABI3）启动子的控制下表达野生型 OZ2 来拯救该缺失突变体。拯救的突变体植物表现出严重的发育延迟和独特的形态表型。遗传和生化分析表明，OZ2 促进了几个线粒体 nad 基因和 rps3 的转录本的剪接。nad 转录本的剪接缺陷导致复合物 I 的不稳定性，这反过来又影响了 oz2 突变体的呼吸能力，开启了替代呼吸途径，并影响了植物的发育。蛋白质-蛋白质相互作用分析表明 OZ2 与几个针对相同剪接事件的已知线粒体剪接因子结合。这些发现将 RanBP2 锌指结构域在核剪接中的已知功能范围扩展到包括植物细胞器剪接。
