Poliovirus RNA Is Released from the Capsid near a Twofold Symmetry Axis
Poliovirus RNA Is Released from the Capsid near a Twofold Symmetry Axis
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DOI：
10.1128/jvi.00531-10
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发表时间：
2011-01-01
影响因子：
5.4
通讯作者：
Hogle, James M.
中科院分区：
文献类型：
--
作者：
Bostina, Mihnea;Levy, Hazel;Hogle, James M.
在识别并结合宿主细胞后，脊髓灰质炎病毒（像其他非包膜病毒一样）面临着将其基因组跨细胞膜易位并进入细胞质的挑战。为了避免与衣壳纠缠，RNA必须通过病毒粒子表面的单个位点退出。然而，单个位点（从60个等价物中）选择的机制尚不清楚；到目前为止，甚至它在病毒粒子表面的位置也一直存在争议。为了帮助阐明感染的机制，我们使用了单粒子冷冻电子显微镜和断层扫描来重建在脊髓灰质炎病毒感染过程的各个阶段由脊髓灰质炎病毒形成的构象改变的中间体。最近，我们报道了两种形式的终态80S空衣壳粒子的二十面对称结构。令人惊讶的是，RNA在衣壳附近经常可见；在病毒粒子的一个子集中，在衣壳的内外都可以看到RNA，它们正在离开。为了可视化RNA的存在，我们现在已经确定了该子集的不对称重建，使用单粒子低温电子显微镜和低温电子断层扫描方法，在类似于50埃的分辨率下产生独立的重建。与文献预测相反，RNA在衣壳表面的足迹位于病毒2重轴附近，覆盖密度降低的槽形区域，这在两种对称的80S重建中都存在，并且从2重轴向每个相邻的5重轴延伸约20埃。
After recognizing and binding to its host cell, poliovirus (like other nonenveloped viruses) faces the challenge of translocating its genome across a cellular membrane and into the cytoplasm. To avoid entanglement with the capsid, the RNA must exit via a single site on the virion surface. However, the mechanism by which a single site is selected (from among 60 equivalents) is unknown; and until now, even its location on the virion surface has been controversial. To help to elucidate the mechanism of infection, we have used single-particle cryoelectron microscopy and tomography to reconstruct conformationally altered intermediates that are formed by the poliovirion at various stages of the poliovirus infection process. Recently, we reported icosahedrally symmetric structures for two forms of the end-state 80S empty capsid particle. Surprisingly, RNA was frequently visible near the capsid; and in a subset of the virions, RNA was seen on both the inside and outside of the capsid, caught in the act of exiting. To visualize RNA exiting, we have now determined asymmetric reconstructions from that subset, using both single-particle cryo-electron microscopy and cryo-electron tomographic methods, producing independent reconstructions at similar to 50-angstrom resolution. Contrary to predictions in the literature, the footprint of RNA on the capsid surface is located close to a viral 2-fold axis, covering a slot-shaped area of reduced density that is present in both of the symmetrized 80S reconstructions and which extends by about 20 angstrom away from the 2-fold axis toward each neighboring 5-fold axis.