Graduate School of Natural Sciences, Nagoya City University, Nagoya, Japan.
RNA Biol. 2012 Mar;9(3):302-13. doi: 10.4161/rna.19101. Epub 2012 Mar 1.
Recently, a large number of non-coding RNAs (ncRNAs) have been found in a wide variety of organisms, but their biological functions are poorly understood, except for several tiny RNAs. To identify novel ncRNAs with essential functions in flowering plants, we focused attention on RNA polymerase III (Pol III) and its transcriptional activity, because most Pol III-transcribed RNAs contribute to key processes relating to cell activities, and have highly conserved promoter elements: upstream sequence elements, a TATA-like sequence, and a poly(T) stretch as a transcription terminator. After in silico prediction from the Arabidopsis genome, 20 novel ncRNAs candidates were obtained. AtR8 RNA (approx. 260 nt) and AtR18 RNA (approx. 160 nt) were identified by efficient in vitro transcription by Pol III in tobacco nuclear extracts. AtR8 RNA was conserved among six additional taxa of Brassicaceae, and the secondary structure of the RNA was also conserved among the orthologs. Abundant accumulation of AtR8 RNA was observed in the plant roots and cytosol of cultured cells. The RNA was not processed into a smaller fragment and no short open reading frame was included. Remarkably, expression of the AtR8 RNA responded negatively to hypoxic stress, and this regulation evidently differed from that of U6 snRNA.
最近，在各种生物中发现了大量的非编码 RNA（ncRNAs），但除了少数几种小 RNA 外，它们的生物学功能还了解甚少。为了鉴定在开花植物中具有重要功能的新 ncRNAs，我们将注意力集中在 RNA 聚合酶 III（Pol III）及其转录活性上，因为大多数 Pol III 转录的 RNA 有助于与细胞活动相关的关键过程，并且具有高度保守的启动子元件：上游序列元件、TATA 样序列和作为转录终止子的多（T）延伸。在拟南芥基因组的计算机预测后，获得了 20 个新的 ncRNAs 候选物。通过烟草核提取物中 Pol III 的有效体外转录，鉴定出 AtR8 RNA（约 260nt）和 AtR18 RNA（约 160nt）。AtR8 RNA 在十字花科的另外六个分类群中保守，并且 RNA 的二级结构在同源物中也保守。在植物根和培养细胞的细胞质中大量积累 AtR8 RNA。该 RNA 没有被加工成较小的片段，也没有包含短开放阅读框。值得注意的是，AtR8 RNA 的表达对缺氧胁迫呈负响应，这种调控明显不同于 U6 snRNA。
