Department of Medial Microbiology and Immunology, School of Medicine, University of California Davis, Davis, CA 95616, USA.
Purification Development Department, Genentech, Inc., One DNA Way, South San Francisco, CA 94080, USA.
Viruses. 2022 Jul 19;14(7):1564. doi: 10.3390/v14071564.
Crocodilepox virus (CRV) belongs to the family and mainly infects hatchling and juvenile Nile crocodiles. Most poxviruses encode inhibitors of the host antiviral protein kinase R (PKR), which is activated by viral double-stranded (ds) RNA formed during virus replication, resulting in the phosphorylation of eIF2α and the subsequent shutdown of general mRNA translation. Because CRV lacks orthologs of known poxviral PKR inhibitors, we experimentally characterized one candidate (CRV157), which contains a predicted dsRNA-binding domain. Bioinformatic analyses indicated that CRV157 evolved independently from other poxvirus PKR inhibitors. CRV157 bound to dsRNA, co-localized with PKR in the cytosol, and inhibited PKR from various species. To analyze whether CRV157 could inhibit PKR in the context of a poxvirus infection, we constructed recombinant vaccinia virus strains that contain either CRV157, or a mutant CRV157 deficient in dsRNA binding in a strain that lacks PKR inhibitors. The presence of wild-type CRV157 rescued vaccinia virus replication, while the CRV157 mutant did not. The ability of CRV157 to inhibit PKR correlated with virus replication and eIF2α phosphorylation. The independent evolution of CRV157 demonstrates that poxvirus PKR inhibitors evolved from a diverse set of ancestral genes in an example of convergent evolution.
鳄病毒（CRV）属于痘病毒科，主要感染幼鳄和幼年尼罗鳄。大多数痘病毒编码宿主抗病毒蛋白激酶 R（PKR）的抑制剂，PKR 是由病毒复制过程中形成的病毒双链 RNA（dsRNA）激活的，导致 eIF2α的磷酸化，随后导致一般 mRNA 翻译关闭。由于 CRV 缺乏已知痘病毒 PKR 抑制剂的同源物，我们通过实验对一个候选物（CRV157）进行了特征描述，该候选物包含一个预测的 dsRNA 结合结构域。生物信息学分析表明，CRV157 是从其他痘病毒 PKR 抑制剂中独立进化而来的。CRV157 与 dsRNA 结合，在细胞质中与 PKR 共定位，并抑制来自不同物种的 PKR。为了分析 CRV157 是否可以在痘病毒感染的情况下抑制 PKR，我们构建了包含 CRV157 或突变型 CRV157（缺乏 dsRNA 结合能力）的重组痘苗病毒株，在缺乏 PKR 抑制剂的病毒株中。野生型 CRV157 的存在挽救了痘苗病毒的复制，而 CRV157 突变体则没有。CRV157 抑制 PKR 的能力与病毒复制和 eIF2α 磷酸化相关。CRV157 的独立进化表明，痘病毒 PKR 抑制剂是从一组多样化的祖先基因中进化而来的，这是趋同进化的一个例子。
