Division of Biotechnology and Molecular Medicine and Department of Pathobiological Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, LA 70803, USA.
College of Veterinary Medicine, University of the Philippines Los Baños, Los Baños, Laguna 4031, Philippines.
Viruses. 2022 Oct 4;14(10):2189. doi: 10.3390/v14102189.
The alphaherpesvirus UL37 tegument protein is a highly conserved, multi-functional protein. Mutagenesis analysis delineated the UL37 domains necessary for retrograde transport and viral replication. Specifically, the amino-terminal 480 amino acids are dispensable for virus replication in epithelial cell culture, but it is unknown whether this amino-terminal deletion affects UL37 structure and intracellular transport in epithelial cells and neurons. To investigate the structure and function of UL37, we utilized multiple computational approaches to predict and characterize the secondary and tertiary structure and other functional features. The structure of HSV-1 UL37 and Δ481N were deduced using publicly available predictive algorithms. The predicted model of HSV-1 UL37 is a stable, multi-functional, globular monomer, rich in alpha helices, with unfolded regions within the linker and the C-tail domains. The highly flexible C-tail contains predicted binding sites to the dynein intermediate chain, as well as DNA and RNA. Predicted interactions with the cytoplasmic surface of the lipid membrane suggest UL37 is a peripheral membrane protein. The Δ481N truncation did not alter the predicted structure of the UL37 C-terminus protein and its predicted interaction with dynein. We validated these models by examining the replication kinetics and transport of the Δ481N virus toward the nuclei of infected epithelial and neuronal cells. The Δ481N virus had substantial defects in virus spread; however, it exhibited no apparent defects in virus entry and intracellular transport. Using computational analyses, we identified several key features of UL37, particularly the flexible unstructured tail; we then demonstrated that the UL37 C-terminus alone is sufficient to effectively transport the virus towards the nucleus of infected epithelial and neuronal cells.
α疱疹病毒 UL37 衣壳蛋白是一种高度保守的多功能蛋白。诱变分析描绘了 UL37 逆行运输和病毒复制所需的结构域。具体来说，氨基末端的 480 个氨基酸对于上皮细胞培养中的病毒复制是可有可无的，但尚不清楚这种氨基末端缺失是否会影响上皮细胞和神经元中的 UL37 结构和细胞内运输。为了研究 UL37 的结构和功能，我们利用多种计算方法来预测和描述其二级和三级结构以及其他功能特征。使用公开可用的预测算法推导出 HSV-1 UL37 和 Δ481N 的结构。HSV-1 UL37 的预测模型是一个稳定的、多功能的球形单体，富含α螺旋，连接区和 C 尾区无规则卷曲。高度灵活的 C 尾包含与动力蛋白中间链以及 DNA 和 RNA 结合的预测结合位点。与质膜细胞质表面的预测相互作用表明 UL37 是一种外周膜蛋白。Δ481N 截断并没有改变 UL37 C 端蛋白的预测结构及其与动力蛋白的预测相互作用。我们通过检查 Δ481N 病毒向感染的上皮和神经元细胞核的复制动力学和运输来验证这些模型。Δ481N 病毒在病毒传播方面存在严重缺陷；然而，它在病毒进入和细胞内运输方面没有明显缺陷。通过计算分析，我们确定了 UL37 的几个关键特征，特别是灵活的无规卷曲的尾部；然后，我们证明了仅 UL37 C 端就足以有效地将病毒运输到感染的上皮和神经元细胞的核内。
