Department of Plant and Environmental Sciences, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Givat-Ram, Jerusalem 91904, Israel.
Department of Biochemistry and Cell Biology, State University of New York, Stony Brook, NY 11794, USA.
Int J Mol Sci. 2017 Nov 17;18(11):2428. doi: 10.3390/ijms18112428.
Plant mitochondria are remarkable with respect to the presence of numerous group II introns which reside in many essential genes. The removal of the organellar introns from the coding genes they interrupt is essential for respiratory functions, and is facilitated by different enzymes that belong to a diverse set of protein families. These include maturases and RNA helicases related proteins that function in group II intron splicing in different organisms. Previous studies indicate a role for the nMAT2 maturase and the RNA helicase PMH2 in the maturation of different pre-RNAs in Arabidopsis mitochondria. However, the specific roles of these proteins in the splicing activity still need to be resolved. Using transcriptome analyses of Arabidopsis mitochondria, we show that nMAT2 and PMH2 function in the splicing of similar subsets of group II introns. Fractionation of native organellar extracts and pulldown experiments indicate that nMAT2 and PMH2 are associated together with their intron-RNA targets in large ribonucleoprotein particle in vivo. Moreover, the splicing efficiencies of the joint intron targets of nMAT2 and PMH2 are more strongly affected in a double mutant-line. These results are significant as they may imply that these proteins serve as components of a proto-spliceosomal complex in plant mitochondria.
就存在大量位于许多必需基因中的第二类内含子而言，植物线粒体是显著的。为了实现呼吸功能，必须从它们所中断的编码基因中去除这些细胞器内含子，这一过程由属于不同蛋白家族的不同酶来完成。这些酶包括在不同生物体中参与第二类内含子剪接的成熟酶和 RNA 解旋酶相关蛋白。先前的研究表明，nMAT2 成熟酶和 RNA 解旋酶 PMH2 在拟南芥线粒体不同前 RNA 的成熟过程中发挥作用。然而，这些蛋白在剪接活性中的具体作用仍有待解决。通过对拟南芥线粒体的转录组分析，我们表明 nMAT2 和 PMH2 可作用于相似的第二类内含子亚类的剪接。天然细胞器提取物的分级分离和下拉实验表明，nMAT2 和 PMH2 与其内含子 RNA 靶标一起在体内与大核糖核蛋白颗粒相关。此外，nMAT2 和 PMH2 的共同内含子靶标的剪接效率在双突变体系中受到更强的影响。这些结果意义重大，因为它们可能意味着这些蛋白作为植物线粒体原剪接体复合物的组成部分发挥作用。
