Phylogenetic analysis of ribonuclease H domains suggests a late, chimeric origin of LTR retrotransposable elements and retroviruses
Phylogenetic analysis of ribonuclease H domains suggests a late, chimeric origin of LTR retrotransposable elements and retroviruses
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DOI：
10.1101/gr.185101
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发表时间：
2001-07-01
期刊：
影响因子：
7
通讯作者：
Eickbush, TH
中科院分区：
文献类型：
--
作者：
Malik, HS;Eickbush, TH
我们已经对真细菌、真核生物、所有携带长期重复序列(LTR)的反转录转座子和几类晚期分枝的非LTR反转录转座子中存在的核糖核酸酶HI(RNH)结构域进行了系统发育分析。对这些不同来源的简单但高度保守的酶结构域的分析为真核反转录转座子的进化提供了令人惊讶的见解。首先，它表明导致脊椎动物逆转录病毒的元件谱系从非LTR反转录转座子或真核宿主基因组获得了一个新的RNH结构域。先前存在的逆转录病毒RNH结构域退化为逆转录酶(RT)-RNH复合体的系链(连接)结构域。第二，这表明所有的LTR反转录转座子在真核生物中都是在非LTR反转录转座子起源之后才出现的。由于LTR反转录转座子的年龄较小，结构复杂，并且没有任何原核前体，我们认为LTR反转录转座子起源于DNA介导的转座子和非LTR反转录转座子的融合。由此产生的LTR逆转录转座的两步机制，即RNA从染色体靶部位反转录而不是直接转录到靶部位，可能是对真核细胞转录和翻译解偶联的一种适应。
We have conducted a phylogenetic analysis of the Ribonuclease HI (RNH) domains present in Eubacteria, Eukarya, all long-term repeat (LTR)-bearing retrotransposons, and several late-branching clades of non-LTR retrotransposons. Analysis of this simple yet highly conserved enzymatic domain From these disparate sources provides surprising insights into the evolution of eukaryotic retrotransposons. First, it indicates that the lineage of elements leading to vertebrate retroviruses acquired a new RNH domain either from non-LTR retrorransposons or From a eukaryotic host genome. The preexisting retroviral RNH domain degenerated to become the tether (connection) domain of the reverse transcriptase (RT)-RNH complex. Second, it indicates that all LTR retrotransposons arose in eukaryotes well after the origin of the non-LTR retrotransposons. Because of the younger age of the LTR retrotransposons, their complex structure, and the absence of any prokaryotic precursors, we propose that the LTR retrotransposons originated as a fusion between a DNA-mediated transposon and a non-LTR retrotransposon. The resulting two-step mechanism of LTR retrotransposition, in which RNA is reverse transcribed away from the chromosomal target site, rather than directly onto the target site, was probably an adaptation to the uncoupling of transcription and translation in eukaryotic cells.