间质蛋白介导致瘤疱疹病毒组装释放的机理研究

Herpesviruses constitute an ancient family, whose members can efficiently establish persistent, life-long infections in their respective hosts. Recent progress in both basic and clinical research has shown that viral lytic replication plays a critical role in viral persistent infections and the associated pathogenesis, yet much remains unknown about the molecular mechanisms underlying herpesvirus lytic replication, especially the late phase of virion assembly and egress. Composed of many viral proteins, tegument is a unique structure of a herpesvirus particle and occupies the space between nucleocapsid and envelope. Increasing amount of knowledge has indicated that tegument proteins play critical roles in virion morphogenesis by bridging the nucleocapsid and the envelope. Using murine gammaherpesvirus 68 (MHV-68) as a model, we have systematically investigated the virion assembly and egress process of gammaherpesviruses and identified several tegument proteins that play essential roles in this process, including ORF33, ORF45 and ORF52. In this application, we plan to integrate molecular and cellular biology, genetics, proteomics and bioimaging approaches, and propose the following aims: 1) to investigate the molecular mechanisms mediating the functional roles of ORF33 and ORF45 in nuclear egress of MHV-68 nucleocapsids; 2) to study the molecular mechanisms mediating the essential roles of ORF33 and ORF45 in cytoplasmic maturation of MHV-68 virions; 3) to identify viral and cellular proteins that interact with ORF52 and investigate the role of these interactions in mediating secondary envelopment of virions as well as the underlying molecular mechanisms. Our results will lead to a deeper understanding of the molecular mechanisms involved in herpesvirus lytic replication and provide insights into developing new therapeutic approaches to prevent and control viral persistent infections.

疱疹病毒是一个古老的家族，一旦入侵宿主便能建立持续性感染，使宿主成为终身携带者。近期临床和基础研究数据表明，裂解复制对疱疹病毒的持续性感染及致病性至关重要，但裂解复制特别是病毒颗粒组装与释放的分子机制仍有诸多不明之处。间质（tegument）是疱疹病毒特有的一个结构成分，位于囊膜和核衣壳之间，由多种病毒蛋白组成，在病毒颗粒的组装与释放过程中起着关键的桥梁作用。我们以鼠疱疹病毒68为模型，对γ疱疹病毒的组装释放过程进行了系统研究，鉴定出在此过程中起关键作用的间质蛋白ORF33、ORF45及ORF52等。本项目拟在此基础上，综合多种技术手段，解析ORF33、ORF45介导病毒衣壳的核释放以及病毒颗粒在细胞质中成熟的分子机制，阐明ORF52及其相互作用蛋白ORF42在病毒颗粒组装与释放中的作用与机理。研究结果将帮助深入理解疱疹病毒裂解复制的分子机理，为防控病毒持续性感染提供理论依据。

EB病毒和卡波西氏肉瘤相关疱疹病毒是两种人类疱疹病毒，其感染后能引起鼻咽癌和淋巴癌等恶性肿瘤。临床和基础研究表明，疱疹病毒的裂解复制对其致瘤至关重要。在病毒裂解复制的后期，病毒核衣壳在细胞核内组装，随后通过核释放转运到细胞质中，进一步获取一系列的间质蛋白（“间质化”）和囊膜（“二次囊膜化”）。间质层是疱疹病毒特有的结构，位于核衣壳和囊膜之间，由多种间质蛋白组成。我们以鼠疱疹病毒68为模型，系统研究了间质蛋白在γ疱疹病毒组装释放过程的作用和分子机理。首先鉴定了MHV-68核释放复合体；发现间质蛋白ORF33和ORF45与核释放复合体具有相互作用，在核释放过程中起到冗余但重要的作用。阐明了ORF33和ORF45的相互作用对于病毒颗粒在细胞质中的成熟至关重要；发现间质蛋白ORF52通过液液相分离介导“病毒颗粒组装区间”的形成。发现间质蛋白ORF38通过与ORF33的相互作用介导了病毒的二次囊膜化；间质蛋白ORF42在病毒二次囊膜化后期的出芽过程中发挥了重要作用。此外，阐明了间质蛋白ORF33和ORF52在病毒感染早期抑制宿主天然免疫的分子机理。该系列研究结果帮助我们深入理解疱疹病毒裂解复制的分子机理，为防控病毒持续性感染提供理论依据。