Assembly and release of respiratory syncytial virus (RSV) virions

A mature virion of the respiratory syncytial virus (RSV) consists of the ribonucleoprotein complex (RNP) surrounded by the protein matrix and a lipid bilayer envelope. The RNP is composed of the genomic negative sense single-stranded (-ssRNA) that is tightly associated with the N protein (nucleoprotein) and the RNA-dependent RNA polymerase complex (RdRP). The RdRP consists of the L protein subunit (large polymerase subunit), the P protein subunit (phosphoprotein polymerase cofactor), and the M2-1 protein, which acts as a transcription processivity factor. The matrix consists of the M (matrix) protein. The M2-1 protein serves as the bridge between the RNP and the M protein. The matrix supports the viral envelope. The viral envelope contains three embedded viral proteins: fusion protein (F), attachment protein (G), and a small hydrophobic protein (SH). The M protein associates with the cytoplasmic domain of the F protein. The SH protein forms a pentameric ion channel in the viral envelope and is thought to delay apoptosis of infected cells. The assembly and budding of RSV virions primarily occurs at the apical surface of ciliated airway epithelial cells where viral filaments containing RNPs form. The budding of RSV virions requires interactions between viral proteins, host cytoskeletal proteins, and membrane. For review, please refer to Shaikh and Crowe 2013, and Battles and McLellan 2019.<br><br>Based on the findings that P, M, and F proteins are sufficient for formation of viral‑like particles (VLPs), P protein, particularly its highly phosphorylated serine/threonine‑rich region between amino acids 39 and 57 that likely interacts with M and/or F proteins, may play an important role in the assembly (Meshram and Oomens 2019).

成熟呼吸道合胞病毒（RSV）的病毒颗粒由核糖核蛋白复合物（RNP）包裹，RNP周围是蛋白质基质和脂质双层包膜。RNP由紧密关联的N蛋白（核蛋白）和RNA依赖性RNA聚合酶复合物（RdRP）的负链单链RNA（-ssRNA）组成。RdRP由L蛋白亚基（大聚合酶亚基）、P蛋白亚基（磷酸蛋白聚合酶辅因子）和M2-1蛋白组成，M2-1蛋白充当转录过程性因子。基质由M蛋白（基质蛋白）组成。M2-1蛋白作为RNP与M蛋白之间的桥梁。基质支撑着病毒包膜。病毒包膜包含三种嵌入的病毒蛋白：融合蛋白（F）、附着蛋白（G）和一种小疏水性蛋白（SH）。M蛋白与F蛋白的细胞质域相联。SH蛋白在病毒包膜中形成五聚体离子通道，并被认为可以延缓感染细胞的凋亡。RSV病毒颗粒的组装和芽生主要发生在纤毛气道上皮细胞的顶端表面，其中包含RNP的病毒丝状体形成。RSV病毒颗粒的芽生需要病毒蛋白、宿主细胞骨架蛋白和膜之间的相互作用。欲深入了解，请参阅Shaikh和Crowe于2013年的著作，以及Battles和McLellan于2019年的研究。基于P、M和F蛋白足以形成病毒类似颗粒（VLPs）的发现，P蛋白，尤其是其富含丝氨酸/苏氨酸的39至57位氨基酸之间的高度磷酸化区域，很可能与M蛋白和/或F蛋白相互作用，可能在组装过程中发挥重要作用（Meshram和Oomens，2019年）。