Manivannan Sathiya N, Lai Lien B, Gopalan Venkat, Simcox Amanda
Molecular Cellular Developmental Biology Program, Ohio State University, Columbus, Ohio, United States of America; Department of Molecular Genetics, Ohio State University, Columbus, Ohio, United States of America.
Department of Chemistry and Biochemistry, Ohio State University, Columbus, Ohio, United States of America; Center for RNA Biology, Ohio State University, Columbus, Ohio, United States of America.
PLoS Genet. 2015 Jan 8;11(1):e1004893. doi: 10.1371/journal.pgen.1004893. eCollection 2015 Jan.
Ribonuclease P (RNase P) is an essential enzyme required for 5'-maturation of tRNA. While an RNA-free, protein-based form of RNase P exists in eukaryotes, the ribonucleoprotein (RNP) form is found in all domains of life. The catalytic component of the RNP is an RNA known as RNase P RNA (RPR). Eukaryotic RPR genes are typically transcribed by RNA polymerase III (pol III). Here we showed that the RPR gene in Drosophila, which is annotated in the intron of a pol II-transcribed protein-coding gene, lacks signals for transcription by pol III. Using reporter gene constructs that include the RPR-coding intron from Drosophila, we found that the intron contains all the sequences necessary for production of mature RPR but is dependent on the promoter of the recipient gene for expression. We also demonstrated that the intron-coded RPR copurifies with RNase P and is required for its activity. Analysis of RPR genes in various animal genomes revealed a striking divide in the animal kingdom that separates insects and crustaceans into a single group in which RPR genes lack signals for independent transcription and are embedded in different protein-coding genes. Our findings provide evidence for a genetic event that occurred approximately 500 million years ago in the arthropod lineage, which switched the control of the transcription of RPR from pol III to pol II.
核糖核酸酶P（RNase P）是tRNA 5'端成熟所必需的一种关键酶。虽然在真核生物中存在一种不含RNA、基于蛋白质的RNase P形式，但核糖核蛋白（RNP）形式存在于所有生命域中。RNP的催化成分是一种名为RNase P RNA（RPR）的RNA。真核生物的RPR基因通常由RNA聚合酶III（pol III）转录。在这里，我们表明果蝇中的RPR基因注释在一个由pol II转录的蛋白质编码基因的内含子中，缺乏pol III转录的信号。使用包含果蝇RPR编码内含子的报告基因构建体，我们发现该内含子包含产生成熟RPR所需的所有序列，但依赖于受体基因的启动子进行表达。我们还证明内含子编码的RPR与RNase P共纯化，并且是其活性所必需的。对各种动物基因组中RPR基因的分析揭示了动物界的一个显著划分，即将昆虫和甲壳类动物分为一组，其中RPR基因缺乏独立转录的信号，并嵌入不同的蛋白质编码基因中。我们的研究结果为大约5亿年前在节肢动物谱系中发生的一个遗传事件提供了证据，该事件将RPR转录的控制从pol III切换到了pol II。
