U3 snoRNA genes are multi-copy and frequently linked to U5 snRNA genes in Euglena gracilis.
U3 snoRNA genes are multi-copy and frequently linked to U5 snRNA genes in Euglena gracilis.
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DOI：
10.1186/1471-2164-10-528
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发表时间：
2009-11-16
期刊：
影响因子：
4.4
通讯作者：
Gray MW
中科院分区：
文献类型：
--
作者：
Charette JM;Gray MW
U3 snoRNA是盒C/D小核仁RNA（snoRNA），其参与从核糖体RNA前体（pre-rRNA）释放18 S rRNA的加工事件。虽然U3 snoRNA存在于所有真核生物中，但大多数研究都集中在真菌（特别是酵母），动物和植物中。在原生生物（主要是单细胞真核生物）的广泛的生物学组合中，对U3 snoRNA及其基因的了解相对较少。在Euglenozoon Euglena gracilis中，运动质体原生动物的远亲，Southern分析先前显示至少有13条带与U3 snoRNA杂交，表明存在多个拷贝的U3 snoRNA基因。通过对λ基因组文库的筛选和PCR扩增，我们回收了14个U3 snoRNA基因变体，这些变体通过主要位于U3 3 3 '-茎环结构域的序列异质性来定义。我们鉴定了眼虫U3 snoRNA基因的三种不同的基因组排列：i）独立，ii）与tRNAArg基因连接，iii）与U 5 snRNA基因连接。在排列ii）中，U3 snoRNA基因位于两个相同的tRNAArg基因的上游，所述两个相同的tRNAArg基因相对于U3基因会聚转录。这种情况让人想起以前在锥虫中描述的U3 snoRNA-tRNA基因连锁。我们在这里记录12种不同的U3 snoRNA-U 5 snRNA基因在眼虫中的排列;在每种情况下，U3基因都与下游和收敛方向的U 5基因相连，基因间区域的长度和序列在变体中不同。多个U3 snoRNA-U 5 snRNA基因连锁，基于基因间间隔区内的序列相似性聚集成不同的家族，推测是由基因组、染色体和/或基因座重复引起的。我们讨论了裸藻基因组中存在异常大量的U3 snoRNA基因的可能原因。多个Southern杂交条带的信号强度的可变性提高了裸藻含有天然非整倍体染色体互补的可能性。
U3 snoRNA is a box C/D small nucleolar RNA (snoRNA) involved in the processing events that liberate 18S rRNA from the ribosomal RNA precursor (pre-rRNA). Although U3 snoRNA is present in all eukaryotic organisms, most investigations of it have focused on fungi (particularly yeasts), animals and plants. Relatively little is known about U3 snoRNA and its gene(s) in the phylogenetically broad assemblage of protists (mostly unicellular eukaryotes). In the euglenozoon Euglena gracilis, a distant relative of the kinetoplastid protozoa, Southern analysis had previously revealed at least 13 bands hybridizing with U3 snoRNA, suggesting the existence of multiple copies of U3 snoRNA genes. Through screening of a λ genomic library and PCR amplification, we recovered 14 U3 snoRNA gene variants, defined by sequence heterogeneities that are mostly located in the U3 3'-stem-loop domain. We identified three different genomic arrangements of Euglena U3 snoRNA genes: i) stand-alone, ii) linked to tRNAArg genes, and iii) linked to a U5 snRNA gene. In arrangement ii), the U3 snoRNA gene is positioned upstream of two identical tRNAArg genes that are convergently transcribed relative to the U3 gene. This scenario is reminiscent of a U3 snoRNA-tRNA gene linkage previously described in trypanosomatids. We document here twelve different U3 snoRNA-U5 snRNA gene arrangements in Euglena; in each case, the U3 gene is linked to a downstream and convergently oriented U5 gene, with the intergenic region differing in length and sequence among the variants. The multiple U3 snoRNA-U5 snRNA gene linkages, which cluster into distinct families based on sequence similarities within the intergenic spacer, presumably arose by genome, chromosome, and/or locus duplications. We discuss possible reasons for the existence of the unusually large number of U3 snoRNA genes in the Euglena genome. Variability in the signal intensities of the multiple Southern hybridization bands raises the possibility that Euglena contains a naturally aneuploid chromosome complement.
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