Teng Chang Ying, Dang Yunkun, Danne Jillian C, Waller Ross F, Green Beverley R
Botany Department, University of British Columbia, Vancouver, B.C., Canada ; Life Sciences Department, Ludong University, Yantai, Shandong, China.
PLoS One. 2013 Jun 19;8(6):e65387. doi: 10.1371/journal.pone.0065387. Print 2013.
Dinoflagellates are a large group of algae that contribute significantly to marine productivity and are essential photosynthetic symbionts of corals. Although these algae have fully-functioning mitochondria and chloroplasts, both their organelle genomes have been highly reduced and the genes fragmented and rearranged, with many aberrant transcripts. However, nothing is known about their RNA polymerases. We cloned and sequenced the gene for the nuclear-encoded mitochondrial polymerase (RpoTm) of the dinoflagellate Heterocapsa triquetra and showed that the protein presequence targeted a GFP construct into yeast mitochondria. The gene belongs to a small gene family, which includes a variety of 3'-truncated copies that may have originated by retroposition. The catalytic C-terminal domain of the protein shares nine conserved sequence blocks with other single-subunit polymerases and is predicted to have the same fold as the human enzyme. However, the N-terminal (promoter binding/transcription initiation) domain is not well-conserved. In conjunction with the degenerate nature of the mitochondrial genome, this suggests a requirement for novel accessory factors to ensure the accurate production of functional mRNAs.
甲藻是一大类藻类，对海洋生产力有重要贡献，并且是珊瑚必不可少的光合共生体。尽管这些藻类具有功能完备的线粒体和叶绿体，但它们的细胞器基因组都已高度简化，基因片段化且重排，还有许多异常转录本。然而，关于它们的RNA聚合酶却一无所知。我们克隆并测序了三角异帽藻核编码的线粒体聚合酶（RpoTm）基因，结果表明该蛋白的前序列可将绿色荧光蛋白构建体靶向导入酵母线粒体。该基因属于一个小基因家族，其中包括各种可能通过反转录产生的3'端截短的拷贝。该蛋白的催化性C末端结构域与其他单亚基聚合酶共有九个保守序列块，预计其折叠方式与人类酶相同。然而，N末端（启动子结合/转录起始）结构域的保守性不佳。结合线粒体基因组的简并性质，这表明需要新的辅助因子来确保功能性mRNA的准确产生。
