PDF(Pubmed)
Abstract：
Coronavirus genomes sequester their start codons within stem-loop 5 (SL5), a structured, 5\' genomic RNA element. In most alpha- and betacoronaviruses, the secondary structure of SL5 is predicted to contain a four-way junction of helical stems, some of which are capped with UUYYGU hexaloops. Here, using cryogenic electron microscopy (cryo-EM) and computational modeling with biochemically-determined secondary structures, we present three-dimensional structures of SL5 from six coronaviruses. The SL5 domain of betacoronavirus SARS-CoV-2, resolved at 4.7 Å resolution, exhibits a T-shaped structure, with its UUYYGU hexaloops at opposing ends of a coaxial stack, the T\'s \"arms.\" Further analysis of SL5 domains from SARS-CoV-1 and MERS (7.1 and 6.4-6.9 Å resolution, respectively) indicate that the junction geometry and inter-hexaloop distances are conserved features across the studied human-infecting betacoronaviruses. The MERS SL5 domain displays an additional tertiary interaction, which is also observed in the non-human-infecting betacoronavirus BtCoV-HKU5 (5.9-8.0 Å resolution). SL5s from human-infecting alphacoronaviruses, HCoV-229E and HCoV-NL63 (6.5 and 8.4-9.0 Å resolution, respectively), exhibit the same coaxial stacks, including the UUYYGU-capped arms, but with a phylogenetically distinct crossing angle, an X-shape. As such, all SL5 domains studied herein fold into stable tertiary structures with cross-genus similarities, with implications for potential protein-binding modes and therapeutic targets.
摘要：
冠状病毒基因组在茎环5（SL5）内隔离其起始密码子，一个结构化的，5\'基因组RNA元件。在大多数α-和β-冠状病毒中，预测SL5的二级结构包含螺旋茎的四向连接，其中一些用UUYYGU六角形封顶。这里,使用低温电子显微镜（cryo-EM）和具有生物化学确定的二级结构的计算模型，我们展示了来自6种冠状病毒的SL5的三维结构.β-冠状病毒SARS-CoV-2的SL5结构域，分辨率为4.7µ。呈现出T形结构，其UUYYGU六端位于同轴堆栈的相对两端，“T”的武器。\“对SARS-CoV-1和MERS的SL5域的进一步分析（7.1和6.4-6.9的分辨率，分别）表明，连接几何形状和六环间距离是所研究的感染人类的β冠状病毒的保守特征。MERSSL5域显示额外的三级交互，在非人类感染的β冠状病毒BtCoV-HKU5中也观察到了这一点（分辨率为5.9-8.0）。来自人类感染的字母冠状病毒的SL5，HCoV-229E和HCoV-NL63（分辨率为6.5和8.4-9.0，分别)，展示相同的同轴叠层，包括UUYYGU帽的武器，但是在系统发育上有明显的交叉角度，X形。因此，本文研究的所有SL5结构域都折叠成具有交叉属相似性的稳定三级结构，与潜在的蛋白质结合模式和治疗靶标有关。
