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首页> 外文期刊>Journal of Molecular Biology >Complete modification maps for the cytosolic small and large subunit rRNAs of Euglena gracilis: functional and evolutionary implications of contrasting patterns between the two rRNA components.
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Complete modification maps for the cytosolic small and large subunit rRNAs of Euglena gracilis: functional and evolutionary implications of contrasting patterns between the two rRNA components.

机译：细叶Euglena gracilis胞质小和大亚基rRNA的完整修饰图：两种rRNA组分之间对比模式的功能和进化意义。

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摘要

In the protist Euglena gracilis, the cytosolic small subunit (SSU) rRNA is a single, covalently continuous species typical of most eukaryotes; in contrast, the large subunit (LSU) rRNA is naturally fragmented, comprising 14 separate RNA molecules instead of the bipartite (28S+5.8S) eukaryotic LSU rRNA typically seen. We present extensively revised secondary structure models of the E. gracilis SSU and LSU rRNAs and have mapped the positions of all of the modified nucleosides in these rRNAs (88 in SSU rRNA and 262 in LSU rRNA, with only 3 LSU rRNA modifications incompletely characterized). The relative proportions of ribose-methylated nucleosides and pseudouridine ( approximately 60% and approximately 35%, respectively) are closely similar in the two rRNAs; however, whereas the Euglena SSU rRNA has about the same absolute number of modifications as its human counterpart, the Euglena LSU rRNA has twice as many modifications as the corresponding human LSU rRNA. The increased levels of rRNA fragmentation and modification in E. gracilis LSU rRNA are correlated with a 3-fold increase in the level of mispairing in helical regions compared to the human LSU rRNA. In contrast, no comparable increase in mispairing is seen in helical regions of the SSU rRNA compared to its homologs in other eukaryotes. In view of the reported effects of both ribose-methylated nucleoside and pseudouridine residues on RNA structure, these correlations lead us to suggest that increased modification in the LSU rRNA may play a role in stabilizing a 'looser' structure promoted by elevated helical mispairing and a high degree of fragmentation.
机译：在原生动物Euglena gracilis中，胞质小亚基（SSU）rRNA是大多数真核生物中常见的单个，共价连续物种。相比之下，大亚基（LSU）rRNA是天然片段化的，包含14个独立的RNA分子，而不是通常看到的两部分（28S + 5.8S）真核LSU rRNA。我们提出了广泛修订的细粒肠球菌SSU和LSU rRNA的二级结构模型，并绘制了这些rRNA中所有修饰核苷的位置（SSU rRNA中为88个，LSU rRNA中为262个，只有3个LSU rRNA修饰未完全表征） 。在两个rRNA中，核糖甲基化核苷和假尿苷的相对比例（分别约为60％和35％）非常相似。然而，尽管Euglena SSU rRNA的修饰绝对数量与其人类对应的绝对数量相同，但Euglena LSU rRNA的修饰数量却是相应人类LSU rRNA的两倍。与人LSU rRNA相比，细粒肠杆菌LSU rRNA中rRNA片段化水平和修饰水平的提高与螺旋区错配水平提高了3倍有关。相反，与其他真核生物中的同源物相比，在SSU rRNA的螺旋区域中未发现错配的增加。鉴于已报道的核糖甲基化核苷和假尿苷残基均对RNA结构的影响，这些相关性使我们认为LSU rRNA修饰的增加可能在稳定由较高的螺旋错配和DNA促进的“更松散”的结构中起作用。高度碎片化。

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