Molekulare Botanik, Universität Ulm, Albert-Einstein-Allee 11, 89069, Ulm, Germany.
Plant Mol Biol. 2010 Mar;72(4-5):459-67. doi: 10.1007/s11103-009-9584-9. Epub 2009 Dec 4.
In Arabidopsis thaliana the putative mitochondrial RNA helicases PMH1 and PMH2 are members of the large DEAD-box protein family. Our previous characterization of these proteins revealed that PMH1 and/or PMH2 are part of high molecular weight complexes. Now T-DNA insertion lines were established and characterized for each of these genes. Immunodetection analysis of cell suspension cultures established from pmh1-1 and pmh2-1 mutants revealed that indeed both DEAD-box proteins are detectable in large protein complexes with PMH2 being much more abundant than PMH1. In plants the knockout of PMH2 leads to reduced group II intron splicing efficiency. In addition the steady-state levels of several mature mitochondrial mRNAs are decreased while transcription is not influenced. This molecular phenotype suggests that PMH2 acts at the posttranscriptional level with a potential function as RNA chaperone required for formation or maintenance of complex RNA secondary structures of introns rather than a direct role in splicing. In contrast, the investigation of a pmh1-1 knockout line did not reveal any influence of this protein on processing and abundance of mitochondrial transcripts.
在拟南芥中，假定的线粒体 RNA 解旋酶 PMH1 和 PMH2 是大型 DEAD 盒蛋白家族的成员。我们之前对这些蛋白质的特性分析表明，PMH1 和/或 PMH2 是高分子量复合物的一部分。现在为每个基因建立并表征了 T-DNA 插入系。从 pmh1-1 和 pmh2-1 突变体中建立的细胞悬浮培养物的免疫检测分析表明，实际上这两种 DEAD 盒蛋白都可以在大蛋白复合物中检测到，PMH2 的丰度远高于 PMH1。在植物中，PMH2 的敲除会导致 II 组内含子剪接效率降低。此外，几种成熟的线粒体 mRNA 的稳态水平降低，而转录不受影响。这种分子表型表明 PMH2 在转录后水平发挥作用，作为 RNA 伴侣，对于内含子复杂 RNA 二级结构的形成或维持是必需的，而不是直接参与剪接。相比之下，对 pmh1-1 敲除系的研究并未发现该蛋白对线粒体转录本的加工和丰度有任何影响。
