Molecular Genetics of HSV Reactivation

描述（由申请人提供）：该项目的长期目标是了解控制1型单纯疱疹病毒（HSV-1）从潜伏期重新激活的分子机制。在之前的资助期内，工作主要集中在这个过程中的再激活关键区域（rcr）的作用，以及潜在的基因表达是否以表观遗传的方式受到调节。我们的主要发现是：1)潜伏期间HSV-1裂解基因的抑制与组蛋白修饰有关，而与DNA甲基化无关；2)与RCR相关的组蛋白在潜伏期维持在高乙酰化状态；3)含ctcf的染色质绝缘子样元件位于高乙酰化区域的两侧，阻止转录活性染色质向周围的裂解基因扩散；4)在再激活刺激后，LAT增强子的快速去乙酰化导致LAT丰度急剧下降，ICP0启动子乙酰化。这些数据表明rcr在染色质水平上作为调控元件控制LAT和ICP0的转录。具体来说，rcr的LAT增强子部分和染色质绝缘体一起作为开关，以双相方式调节LAT和ICP0。

DESCRIPTION (provided by applicant): The long-term goal of this project is to understand the molecular mechanism that governs the reactivation of Herpes Simplex Virus type 1 (HSV-1) from latency. Work during the previous funding period has focused on the role of the reactivation critical region (rcr) in this process, and whether latent gene expression was regulated in an epigenetic manner. Our key findings were that: 1) the suppression of HSV-1 lytic genes during latency is associated with histone modifications and not DNA methylation; 2) the histones associated with the rcr are maintained in a hyperacetylated state during latency; 3) CTCF-containing chromatin insulator-like elements flank the region of hyperacetylation, preventing the spread of transcriptionally active chromatin to the surrounding lytic genes and 4) following reactivation stimulus rapid deacetylation of the LAT enhancer is followed by a dramatic decrease in LAT abundance and acetylation of the ICP0 promoter. These data suggest that the rcr functions as a regulatory element that controls LAT and ICP0 transcription at the level of chromatin. Specifically, the LAT enhancer portion of the rcr and a chromatin insulator act together as a switch that regulates LAT and ICP0 in a bi-phasic manner. Based on this new data and drawing from chromatin-level regulatory models employed by cellular chromosomes, we have refined our model for the LAT region's role in reactivation. This model views the LAT region as a regulatory locus that controls the transcriptional permissiveness of ICP0 through epigenetic regulation of histone modifications. This regulatory locus consists of at least three components: 1) the LAT enhancer that controls histone modifications, and has the potential to regulate transcription of both the LAT and ICP0; 2) the CTCF-insulator elements which flank the rcr and regulate the extent of the LAT enhancer's influence, and 3) transcription of the LAT RNA itself, which we hypothesize regulates the insulator. This project will seek to prove our overall hypothesis that regulation of these three components governs the ability of HSV-1 to reactivate. HSV-1 is a persistent infection of humans that causes significant morbidity and mortality. Understanding the mechanism of how stress induces reactivation could lead to new therapies to treat and prevent recurrent disease. At a broader level, understanding the mechanism by which HSV regulates transcription via modulation of chromatin structure will increase our understanding of similar processes and pathways in cellular chromosomes, potentially leading to new therapies for developmental disorders and cancer.