Poised for contagion: Evolutionary origins of the infectious abilities of invertebrate retroviruses
Poised for contagion: Evolutionary origins of the infectious abilities of invertebrate retroviruses
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DOI：
10.1101/gr.145000
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发表时间：
2000-09-01
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;Henikoff, S;Eickbush, TH
系统发育分析表明，携带逆转录转座元件的长末端重复序列（LTR）可以获得额外的开放阅读框，从而能够介导感染。虽然这一过程在脊椎动物逆转录病毒的起源及其包膜 (env) 基因的获得中得到了最好的记录，但类似的独立事件也可能发生在昆虫、线虫和植物中。 env 样基因的起源尚不清楚，并且常常被原始获得的古老性及其快速的进化速度所掩盖。在本报告中，我们提供的证据表明，在 LTR 逆转录转座子向逆转录病毒的其他三种可能转变中，包膜样基因是从病毒来源获得的。首先，吉普赛病毒和相关的LTR逆转录转座元件（昆虫错误病毒）从一类昆虫杆状病毒（无RNA阶段的双链DNA病毒）中获得了包膜样基因。其次，秀丽隐杆线虫基因组中的 Cer 逆转录病毒从白蛉病毒（单双义链 RNA 病毒）来源获得包膜基因。第三，Tas逆转录病毒包膜（Ascaris lumricoides）可能是从疱疹病毒科（双链DNA病毒，无RNA阶段）获得的。这些是逆转录病毒的 env 基因被追溯到其原始来源的唯一案例。这对逆转录病毒的进化史以及所有 LTR 逆转录转座元件成为传染原的潜在能力具有影响。
Phylogenetic analyses suggest that long-terminal repeat (LTR) bearing retrotransposable elements can acquire additional open-reading frames that can enable them to mediate infection. Whereas this process is best documented in the origin of the vertebrate retroviruses and their acquisition of an envelope (env) gene, similar independent events may have occurred in insects, nematodes, and plants. The origins of env-like genes are unclear, and are often masked by the antiquity of the original acquisitions and by their rapid rate of evolution. In this report, we present evidence that in three other possible transitions of LTR retrotransposons to retroviruses, an envelope-like gene was acquired from a viral source. First, the gypsy and related LTR retrotransposable elements (the insect errantiviruses) have acquired their envelope-like gene from a class of insect baculoviruses (double-stranded DNA viruses with no RNA stage). Second, the Cer retroviruses in the Caenorhabditis elegans genome acquired their envelope gene from a Phleboviral (single ambisense-stranded RNA viruses) source. Third, the Tas retroviral envelope (Ascaris lumricoides) may have been obtained from Herpesviridae (double-stranded DNA viruses, no RNA stage). These represent the only cases in which the env gene of a retrovirus has been traced back to its original source. This has implications for the evolutionary history of retroviruses as well as for the potential ability of all LTR-retrotransposable elements to become infectious agents.