Kim Eunseong, Kim Yonggyun
Department of Bioresource Sciences, Andong National University, Andong 36729, Republic of Korea.
PLoS One. 2016 Sep 6;11(9):e0161661. doi: 10.1371/journal.pone.0161661. eCollection 2016.
Translational control is a strategy that various viruses use to manipulate their hosts to suppress acute antiviral response. Polydnaviruses, a group of insect double-stranded DNA viruses symbiotic to some endoparasitoid wasps, are divided into two genera: ichnovirus (IV) and bracovirus (BV). In IV, some Cys-motif genes are known as host translation-inhibitory factors (HTIF). The genome of endoparasitoid wasp Cotesia plutellae contains a Cys-motif gene (Cp-TSP13) homologous to an HTIF known as teratocyte-secretory protein 14 (TSP14) of Microplitis croceipes. Cp-TSP13 consists of 129 amino acid residues with a predicted molecular weight of 13.987 kDa and pI value of 7.928. Genomic DNA region encoding its open reading frame has three introns. Cp-TSP13 possesses six conserved cysteine residues as other Cys-motif genes functioning as HTIF. Cp-TSP13 was expressed in Plutella xylostella larvae parasitized by C. plutellae. C. plutellae bracovirus (CpBV) was purified and injected into non-parasitized P. xylostella that expressed Cp-TSP13. Cp-TSP13 was cloned into a eukaryotic expression vector and used to infect Sf9 cells to transiently express Cp-TSP13. The synthesized Cp-TSP13 protein was detected in culture broth. An overlaying experiment showed that the purified Cp-TSP13 entered hemocytes. It was localized in the cytosol. Recombinant Cp-TSP13 significantly inhibited protein synthesis of secretory proteins when it was added to in vitro cultured fat body. In addition, the recombinant Cp-TSP13 directly inhibited the translation of fat body mRNAs in in vitro translation assay using rabbit reticulocyte lysate. Moreover, the recombinant Cp-TSP13 significantly suppressed cellular immune responses by inhibiting hemocyte-spreading behavior. It also exhibited significant insecticidal activities by both injection and feeding routes. These results indicate that Cp-TSP13 is a viral HTIF.
翻译控制是多种病毒用来操纵宿主以抑制急性抗病毒反应的一种策略。多DNA病毒是一类与某些内寄生蜂共生的昆虫双链DNA病毒，分为两个属：卵蜂病毒（IV）和杆状病毒（BV）。在IV中，一些半胱氨酸基序基因被认为是宿主翻译抑制因子（HTIF）。内寄生蜂小菜蛾盘绒茧蜂的基因组包含一个半胱氨酸基序基因（Cp-TSP13），它与一种被称为十字花科微蛾茧蜂的畸形细胞分泌蛋白14（TSP14）的HTIF同源。Cp-TSP13由129个氨基酸残基组成，预测分子量为13.987 kDa，pI值为7.928。编码其开放阅读框的基因组DNA区域有三个内含子。与其他作为HTIF发挥作用的半胱氨酸基序基因一样，Cp-TSP13具有六个保守的半胱氨酸残基。Cp-TSP13在被小菜蛾盘绒茧蜂寄生的小菜蛾幼虫中表达。纯化小菜蛾盘绒茧蜂杆状病毒（CpBV）并将其注射到表达Cp-TSP13的未被寄生的小菜蛾中。将Cp-TSP13克隆到真核表达载体中，用于感染Sf9细胞以瞬时表达Cp-TSP13。在培养液中检测到合成的Cp-TSP13蛋白。一项覆盖实验表明，纯化的Cp-TSP13进入血细胞。它定位于细胞质中。当重组Cp-TSP13添加到体外培养的脂肪体中时，它显著抑制分泌蛋白的蛋白质合成。此外，在使用兔网织红细胞裂解物的体外翻译试验中，重组Cp-TSP13直接抑制脂肪体mRNA的翻译。此外，重组Cp-TSP13通过抑制血细胞铺展行为显著抑制细胞免疫反应。通过注射和喂食途径，它也表现出显著的杀虫活性。这些结果表明Cp-TSP13是一种病毒HTIF。
