Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
Laboratory of Protein Structure, International Institute of Molecular and Cell Biology, Warsaw, Poland.
Plant Cell Physiol. 2020 Jun 1;61(6):1107-1119. doi: 10.1093/pcp/pcaa040.
RNase H1 is an endonuclease specific toward the RNA strand of RNA:DNA hybrids. Members of this protein family are present in most living organisms and are essential for removing RNA that base pairs with DNA. It prevents detrimental effects of RNA:DNA hybrids and is involved in several biological processes. Arabidopsis thaliana has been previously shown to contain three genes encoding RNase H1 proteins that localize to three distinct cellular compartments. We show that these genes originate from two gene duplication events. One occurred in the common ancestor of dicots and produced nuclear and organellar RNase H1 paralogs. Second duplication occurred in the common ancestor of Brassicaceae and produced mitochondrial- and plastid-localized proteins. These proteins have the canonical RNase H1 activity, which requires at least four ribonucleotides for endonucleolytic digestion. Analysis of mutants in the RNase H1 genes revealed that the nuclear RNH1A and mitochondrial RNH1B are dispensable for development under normal growth conditions. However, the presence of at least one organellar RNase H1 (RNH1B or RNH1C) is required for embryonic development. The plastid-localized RNH1C affects plastid DNA copy number and sensitivity to replicative stress. Our results present the evolutionary history of RNH1 proteins in A. thaliana, demonstrate their canonical RNase H1 activity and indicate their role in early embryonic development.
RNase H1 是一种针对 RNA:DNA 杂种中 RNA 链的内切核酸酶。该蛋白家族的成员存在于大多数生物中，对于去除与 DNA 碱基配对的 RNA 至关重要。它可以防止 RNA:DNA 杂种的有害影响，并参与多种生物过程。先前已经表明，拟南芥含有编码 RNase H1 蛋白的三个基因，这些基因定位于三个不同的细胞区室。我们表明这些基因源自两次基因复制事件。一次发生在双子叶植物的共同祖先中，并产生了核和细胞器 RNase H1 旁系同源物。第二次复制发生在芸薹科植物的共同祖先中，并产生了定位于线粒体和质体的蛋白质。这些蛋白质具有典型的 RNase H1 活性，该活性需要至少四个核糖核苷酸进行内切核酸酶消化。对 RNase H1 基因的突变体进行分析表明，核 RNH1A 和线粒体 RNH1B 在正常生长条件下的发育中是可有可无的。然而，至少有一种细胞器 RNase H1（RNH1B 或 RNH1C）的存在是胚胎发育所必需的。定位于质体的 RNH1C 影响质体 DNA 拷贝数和对复制应激的敏感性。我们的结果呈现了 A. thaliana 中 RNH1 蛋白的进化历史，证明了它们的典型 RNase H1 活性，并表明了它们在早期胚胎发育中的作用。
