KSHV RTA: more than viral replication

描述（由申请人提供）：自从它们存在以来，病毒和它们的宿主细胞之间就存在着无休止的军备竞赛。宿主细胞已经开发出许多策略来沉默病毒基因表达，而病毒总是找到克服这些障碍的方法。因此，病毒已经进化到充分利用现有的细胞染色质成分，在需要时激活或抑制其自身的基因。事实上，疱疹病毒基因组染色质的宿主表观遗传修饰在病毒生命周期中潜伏基因和裂解基因的转录控制中起关键作用。卡波西肉瘤相关疱疹病毒（KSHV）是一种普遍存在的疱疹病毒，在人类中建立终身持续感染，并与卡波西肉瘤和几种淋巴恶性肿瘤相关。在潜伏期，KSHV基因组作为组装成核小体结构的多拷贝环状DNA持续存在。虽然病毒潜伏期的特征在于受限制的病毒基因表达，但再活化诱导裂解性复制程序和病毒基因以限定的顺序和时间顺序表达。我们的初步研究表明：（1）KSHV的潜伏和裂解染色质与激活和抑制组蛋白修饰的独特模式相关，其分布在再激活后以有组织的方式变化，与病毒裂解基因的时间顺序表达相关。此外，（2）进化上保守的Polycomb组蛋白和组蛋白去泛素化酶也通过调节病毒染色质结构在调节KSHV潜伏和再激活中起关键作用。因此，KSHV的表观遗传程序是限制潜在基因表达和裂解基因有序表达的关键。本研究的目的是更好地了解KSHV基因组的表观遗传修饰如何影响病毒潜伏期和裂解性复制，从而有助于体内持续感染和随后致病事件的发展。基于我们的初步研究，我们假设KSHV基因组的适当表观遗传调控对于潜伏期和再激活期间的病毒持续存在以及KSHV感染病变的发病机制至关重要。该提案具有高度创新性，利用完善的全基因组ChIP阵列，BAC遗传学和体内实验条件。

DESCRIPTION (provided by applicant): Ever since their existence, there has been an everlasting arms race between viruses and their host cells. Host cells have developed numerous strategies to silence viral gene expression, whereas viruses always find ways to overcome these obstacles. Accordingly, viruses have evolved to take full advantage of existing cellular chromatin components to activate or repress its own genes when needed. In fact, host epigenetic modifications of the herpesviral genome chromatin play a key role in the transcriptional control of latent and lytic genes during a productive viral lifecycle. Kaposi's sarcoma-associated herpesvirus (KSHV) is a ubiquitous herpesvirus that establishes a life-long persistent infection in humans and is associated with Kaposi's sarcoma and several lymphoid malignancies. During latency, the KSHV genome persists as a multicopy circular DNA assembled into nucleosomal structures. While viral latency is characterized by restricted viral gene expression, reactivation induces the lytic replication program and the expression of viral genes in a defined sequential and temporal order. Our preliminary study demonstrates that (1) the latent and lytic chromatins of KSHV are associated with a distinctive pattern of activating and repressive histone modifications whose distribution changes upon reactivation in an organized manner in correlation with the temporally ordered expression of viral lytic genes. Furthermore, (2) the evolutionarily conserved Polycomb group proteins and histone deubiquitinases also play a critical role in the regulation of KSHV latency and reactivation by regulating the viral chromatin structure. Thus, the epigenetic program of KSHV is at the crux of restricting latent gene expression and the orderly expression of lytic genes. The goal of this study is to better understand how epigenetic modifications of the KSHV genome affect viral latency and lytic replication, to thereby contribute to the development of a persistent infection and subsequent pathogenic events in vivo. Based on our preliminary studies, we hypothesize that the proper epigenetic regulation of the KSHV genome is critical for viral persistency during latency and reactivation, and for pathogenesis in KSHV infected lesions. This proposal is highly innovative, utilizing well-established comprehensive genome-wide ChIP array, BAC genetics, and in vivo experimental conditions.