Department of Microbiology and Institute of Molecular Virology, University of Minnesota, Minneapolis, Minnesota, USA.
J Virol. 2012 Sep;86(18):9995-10005. doi: 10.1128/JVI.01078-12. Epub 2012 Jul 3.
Human cytomegalovirus (HCMV) virions are structurally complex, and the mechanisms by which they are assembled are poorly understood, especially with respect to the cytoplasmic phase of assembly, during which the majority of the tegument is acquired and final envelopment occurs. These processes occur at a unique cytoplasmic structure called the assembly complex, which is formed through a reorganization of the cellular secretory apparatus. The HCMV tegument protein UL99 (pp28) is essential for viral replication at the stage of secondary envelopment. We previously demonstrated that UL99 interacts with the essential tegument protein UL94 in infected cells as well as in the absence of other viral proteins. Here we show that UL94 and UL99 alter each other's localization and that UL99 stabilizes UL94 in a binding-dependent manner. We have mapped the interaction between UL94 and UL99 to identify the amino acids of each protein that are required for their interaction. Mutation of these amino acids in the context of the viral genome demonstrates that HCMV is completely defective for replication in the absence of the interaction between UL94 and UL99. Further, we demonstrate that in the absence of their interaction, both UL94 and UL99 exhibit aberrant localization and do not accumulate at the assembly complex during infection. Taken together, our data suggest that the interaction between UL94 and UL99 is essential for the proper localization of each protein to the assembly complex and thus for the production of infectious virus.
人巨细胞病毒（HCMV）病毒粒子结构复杂，其组装机制了解甚少，特别是在组装的细胞质阶段，在此期间获得了大多数被膜蛋白并发生最终包膜。这些过程发生在一种称为组装复合物的独特细胞质结构中，该复合物是通过细胞分泌装置的重组形成的。HCMV 被膜蛋白 UL99（pp28）在二次包膜阶段对病毒复制至关重要。我们之前证明，在感染细胞中以及在没有其他病毒蛋白的情况下，UL99 与必需的被膜蛋白 UL94 相互作用。在这里，我们显示 UL94 和 UL99 改变彼此的定位，并且 UL99 以依赖结合的方式稳定 UL94。我们已经绘制了 UL94 和 UL99 之间的相互作用图，以确定每个蛋白质相互作用所需的氨基酸。在病毒基因组的背景下突变这些氨基酸表明，在没有 UL94 和 UL99 相互作用的情况下，HCMV 的复制完全有缺陷。此外，我们证明在没有相互作用的情况下，UL94 和 UL99 均表现出异常定位，并且在感染过程中不会在组装复合物处积累。总之，我们的数据表明，UL94 和 UL99 之间的相互作用对于每种蛋白质正确定位到组装复合物以及产生感染性病毒至关重要。
