An Ascovirus-Encoded RNase III Autoregulates Its Expression and Suppresses RNA Interference-Mediated Gene Silencing
An Ascovirus-Encoded RNase III Autoregulates Its Expression and Suppresses RNA Interference-Mediated Gene Silencing
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DOI：
10.1128/jvi.02362-09
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发表时间：
2010-04-01
影响因子：
5.4
通讯作者：
Asgari, Sassan
中科院分区：
文献类型：
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作者：
Hussain, Mazhar;Abraham, Alexander M.;Asgari, Sassan
RNaseIII蛋白在几种类型的RNA分子的加工和基因沉默中起着至关重要的作用。最近，人们发现一些植物和动物病毒也编码类似RNaseIII的蛋白。对属于Ascoviridae家族的四种病毒进行的基因组测序显示，这些病毒之间存在一个RNaseIII开放阅读框架。这些还没有在寄生虫病毒中被探索，因此它们在宿主-病毒相互作用中的作用是未知的。在这里，我们证实了绿色日光夜蛾病毒(HvAV-3E)开放阅读框27(Orf27)的表达，该蛋白在感染后编码一个类似RNaseIII的蛋白，并证明了编码蛋白的dsRNA特异性内切核酸酶活性。对orf27在病毒感染的昆虫细胞和细菌表达系统中的表达模式的分析表明，该蛋白随着时间的推移而自我调节。此外，利用RNA干扰(RNAi)介导的基因沉默，发现HvAV-3E RNase III对病毒DNA复制和感染是必不可少的。此外，我们还利用绿色荧光蛋白基因作为标记，为RNaseIII参与抑制基因沉默提供了证据。据我们所知，这是第一个描述和显示抑制宿主细胞RNAi防御机制的昆虫病毒编码的RNaseIII。
RNase III proteins play vital roles in processing of several types of RNA molecules and gene silencing. Recently, it has been discovered that some plant and animal viruses encode RNase III-like proteins as well. Genome sequencing of four virus species belonging to the Ascoviridae family has revealed sequence conservation of an RNase III open reading frame among the viruses. These have not been explored in ascoviruses, and therefore their role in host-virus interaction is unknown. Here, we confirmed expression of Heliothis virescens ascovirus (HvAV-3e) open reading frame 27 (orf27) that encodes an RNase III-like protein after infection and demonstrated dsRNA specific endoribonuclease activity of the encoded protein. Analysis of the expression patterns of orf27 in virus-infected insect cells and a bacterial expression system revealed autoregulation of this protein over time. Moreover, HvAV-3e RNase III was found essential for virus DNA replication and infection using RNA interference (RNAi)-mediated gene silencing. In addition, using green fluorescent protein gene as a marker, we provide evidence that RNase III is involved in the suppression of gene silencing. To our knowledge, this is the first insect virus-encoded RNase III described and shown to suppress host cell RNAi defense mechanism.