Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
Department of Biological Sciences, Columbia University, New York, NY, USA.
EMBO J. 2019 Oct 4;38(21):e102226. doi: 10.15252/embj.2019102226. Epub 2019 Oct 14.
Colony collapse disorder (CCD) is a multi-faceted syndrome decimating bee populations worldwide, and a group of viruses of the widely distributed Dicistroviridae family have been identified as a causing agent of CCD. This family of viruses employs non-coding RNA sequences, called internal ribosomal entry sites (IRESs), to precisely exploit the host machinery for viral protein production. Using single-particle cryo-electron microscopy (cryo-EM), we have characterized how the IRES of Israeli acute paralysis virus (IAPV) intergenic region captures and redirects translating ribosomes toward viral RNA messages. We reconstituted two in vitro reactions targeting a pre-translocation and a post-translocation state of the IAPV-IRES in the ribosome, allowing us to identify six structures using image processing classification methods. From these, we reconstructed the trajectory of IAPV-IRES from the early small subunit recruitment to the final post-translocated state in the ribosome. An early commitment of IRES/ribosome complexes for global pre-translocation mimicry explains the high efficiency observed for this IRES. Efforts directed toward fighting CCD by targeting the IAPV-IRES using RNA-interference technology are underway, and the structural framework presented here may assist in further refining these approaches.
群体崩溃紊乱（CCD）是一种多方面的综合征，正在使世界各地的蜜蜂种群大量减少，而广泛分布的双 RNA 病毒科（Dicistroviridae）中的一组病毒已被确定为 CCD 的致病因子。该病毒家族使用非编码 RNA 序列，称为内部核糖体进入位点（IRES），以精确利用宿主机制进行病毒蛋白的生产。使用单颗粒冷冻电子显微镜（cryo-EM），我们描述了以色列急性麻痹病毒（IAPV）基因间区的 IRES 如何捕获并将翻译核糖体重新定向到病毒 RNA 消息。我们重建了针对 IAPV-IRES 在核糖体中的前移位和后移位状态的两个体外反应，这使我们能够使用图像处理分类方法识别六个结构。从中，我们重建了 IAPV-IRES 从小亚基招募到核糖体中最终后移位状态的轨迹。IRES/核糖体复合物早期对全局前移位模拟的承诺解释了这种 IRES 观察到的高效率。目前正在通过使用 RNA 干扰技术靶向 IAPV-IRES 来对抗 CCD，这里提出的结构框架可能有助于进一步改进这些方法。
