Kruszka Katarzyna, Barneche Fredy, Guyot Romain, Ailhas Jérôme, Meneau Isabelle, Schiffer Steffen, Marchfelder Anita, Echeverría Manuel
Laboratoire Génome et Développement des Plantes, UMR CNRS 5096, Université de Perpignan, 66860 Perpignan cedex, France.
EMBO J. 2003 Feb 3;22(3):621-32. doi: 10.1093/emboj/cdg040.
Small nucleolar RNAs (snoRNAs) guiding modifications of ribosomal RNAs and other RNAs display diverse modes of gene organization and expression depending on the eukaryotic system: in animals most are intron encoded, in yeast many are monocistronic genes and in plants most are polycistronic (independent or intronic) genes. Here we report an unprecedented organization: plant dicistronic tRNA-snoRNA genes. In Arabidopsis thaliana we identified a gene family encoding 12 novel box C/D snoRNAs (snoR43) located just downstream from tRNA(Gly) genes. We confirmed that they are transcribed, probably from the tRNA gene promoter, producing dicistronic tRNA(Gly)-snoR43 precursors. Using transgenic lines expressing a tagged tRNA-snoR43.1 gene we show that the dicistronic precursor is accurately processed to both snoR43.1 and tRNA(Gly). In addition, we show that a recombinant RNase Z, the plant tRNA 3' processing enzyme, efficiently cleaves the dicistronic precursor in vitro releasing the snoR43.1 from the tRNA(Gly). Finally, we describe a similar case in rice implicating a tRNA(Met-e) expressed in fusion with a novel C/D snoRNA, showing that this mode of snoRNA expression is found in distant plant species.
引导核糖体RNA及其他RNA进行修饰的小核仁RNA（snoRNA），其基因组织和表达模式因真核生物系统而异：在动物中，大多数snoRNA由内含子编码；在酵母中，许多是单顺反子基因；而在植物中，大多数是多顺反子（独立或内含子）基因。在此，我们报道了一种前所未有的基因组织形式：植物双顺反子tRNA-snoRNA基因。在拟南芥中，我们鉴定出一个基因家族，其编码12个新的C/D盒式snoRNA（snoR43），这些snoRNA位于tRNA（Gly）基因的下游。我们证实它们可能从tRNA基因启动子转录而来，产生双顺反子tRNA（Gly）-snoR43前体。利用表达带标签的tRNA-snoR43.1基因的转基因株系，我们发现双顺反子前体能够准确加工成snoR43.1和tRNA（Gly）。此外，我们还表明，植物tRNA 3'加工酶重组核糖核酸酶Z在体外能有效切割双顺反子前体，从tRNA（Gly）上释放出snoR43.1。最后，我们描述了水稻中的一个类似案例，涉及一个与新的C/D snoRNA融合表达的tRNA（Met-e），表明这种snoRNA表达模式在远缘植物物种中也存在。
