Department of Microbiology, University of Iowa, Iowa City, Iowa, USA.
J Virol. 2014 Apr;88(8):4058-68. doi: 10.1128/JVI.03707-13. Epub 2014 Jan 22.
The herpes simplex virus 1 (HSV-1) UL51 gene encodes a 244-amino-acid (aa) palmitoylated protein that is conserved in all herpesviruses. The alphaherpesvirus UL51 (pUL51) protein has been reported to function in nuclear egress and cytoplasmic envelopment. No complete deletion has been generated because of the overlap of the UL51 coding sequence 5' end with the UL52 promoter sequences, but partial deletions generated in HSV and pseudorabies virus (PrV) suggest an additional function in epithelial cell-to-cell spread. Here we show partial uncoupling of the replication, release, and cell-to-cell spread functions of HSV-1 pUL51 in two ways. Viruses in which aa 73 to 244 were deleted from pUL51 or in which a conserved YXXΦ motif near the N terminus was altered showed cell-specific defects in spread that cannot be accounted for by defects in replication and virus release. Also, a cell line that expresses C-terminally enhanced green fluorescent protein (EGFP)-tagged pUL51 supported normal virus replication and release into the medium but the formation of only small plaques. This cell line also failed to support normal localization of gE to cell junctions. gE and pUL51 partially colocalized in infected cells, and these two proteins could be coimmunoprecipitated from infected cells, suggesting that they can form a complex during infection. The cell-to-cell spread defect associated with the pUL51 mutation was more severe than that associated with gE-null virus, suggesting that pUL51 has gE-independent functions in epithelial cell spread.
Herpesviruses establish and reactivate from lifelong latency in their hosts. When they reactivate, they are able to spread within their hosts despite the presence of a potent immune response that includes neutralizing antibody. This ability is derived in part from a specialized mechanism for virus spread between cells. Cell-to-cell spread is a conserved property of herpesviruses that likely relies on conserved viral genes. An understanding of their function may aid in the design of vaccines and therapeutics. Here we show that one of the conserved viral genes, UL51, has an important role in cell-to-cell spread in addition to its previously demonstrated role in virus assembly. We find that its function depends on the type of cell that is infected, and we show that it interacts with and modulates the function of another viral spread factor, gE.
单纯疱疹病毒 1 (HSV-1) UL51 基因编码一个 244 个氨基酸的棕榈酰化蛋白，该蛋白在所有疱疹病毒中都保守。α疱疹病毒 UL51 (pUL51) 蛋白已被报道在核出芽和细胞质包膜化中发挥作用。由于 UL51 编码序列 5'端与 UL52 启动子序列重叠，因此无法产生完整的缺失，但在单纯疱疹病毒和伪狂犬病病毒 (PrV) 中产生的部分缺失表明其在上皮细胞间传播中具有额外的功能。在这里，我们通过两种方式显示了 HSV-1 pUL51 的复制、释放和细胞间传播功能的部分解偶联。从 pUL51 中缺失 aa73 到 244 或改变靠近 N 端的保守 YXXΦ 基序的病毒在传播中表现出细胞特异性缺陷，这些缺陷不能用复制和病毒释放的缺陷来解释。此外，表达 C 末端增强型绿色荧光蛋白 (EGFP) 标记的 pUL51 的细胞系支持正常的病毒复制和释放到培养基中，但仅形成小斑。该细胞系也未能支持 gE 正常定位于细胞连接。gE 和 pUL51 在感染细胞中部分共定位，并且这两种蛋白质可以从感染细胞中共同免疫沉淀，表明它们可以在感染过程中形成复合物。与 pUL51 突变相关的细胞间传播缺陷比与 gE 缺失病毒相关的缺陷更严重，表明 pUL51 在上皮细胞传播中具有 gE 独立的功能。
疱疹病毒在其宿主中建立并从终身潜伏中重新激活。当它们重新激活时，尽管存在包括中和抗体在内的强大免疫反应，但它们能够在宿主内传播。这种能力部分源自病毒在细胞间传播的专门机制。细胞间传播是疱疹病毒的一种保守特性，可能依赖于保守的病毒基因。对其功能的理解可能有助于疫苗和治疗剂的设计。在这里，我们表明，在其先前证明的在病毒组装中的作用之外，保守病毒基因 UL51 在细胞间传播中具有重要作用。我们发现其功能取决于被感染的细胞类型，并且我们表明它与另一种病毒传播因子 gE 相互作用并调节其功能。
