Escape from gammaherpesvirus-induced mRNA destruction

描述(由申请人提供)：伽玛疱疹病毒卡波西肉瘤相关疱疹病毒(KSHV)和爱泼斯坦-巴尔病毒(EBV)是免疫功能低下的人患癌症的主要原因。就KSHV而言，撒哈拉以南非洲的感染率可达80%，因此，那里的卡波西氏肉瘤的发病率正在上升，并正在成为最常见的成人恶性肿瘤之一。这些大的双链DNA病毒在裂解复制过程中被放大，但在宿主的整个生命周期中处于非复制的潜伏状态。虽然肿瘤的发生主要与病毒的潜伏形式有关，但由于KSHV的潜伏期通常不是一个转化事件，KSHV诱导的疾病也需要低水平的持续裂解复制。裂解复制既是感染幼稚细胞的新病毒的来源，也是促进潜伏感染细胞生长和创造合适的肿瘤微环境的病毒和宿主旁分泌因子的产生所必需的。然而，在溶血性伽马疱疹病毒感染过程中出现的一个突出的表型是细胞信使RNA(MRNA)的广泛破坏，它有效地抑制宿主基因的表达。因此，裂解感染细胞诱导特定宿主基因的必要性和随之而来的细胞基因表达的阻断之间存在矛盾。这个项目的目标是机械地确定特定的宿主基因是如何逃避破坏的。裂解感染过程中mRNA的降解是由病毒Sox蛋白协调细胞RNA周转因子来执行基因表达的关闭。有趣的是，我们观察到，白介素6(IL-6)等精选信息对SOX诱导的营业额直接无效。在IL-6的情况下，我们已经将一个顺式作用的逃逸元件映射到其3‘非翻译区的一个区域，并鉴定了几个与该RNA元件复合的宿主蛋白。因此，该项目的一个方面是探索这些RNA-蛋白质相互作用的机制后果，并确定它们在SOX存在和不存在的情况下如何影响IL-6mRNA的稳定性。鉴于IL-6在人类疾病中的众多作用，这一信息将与KSHV诱导的肿瘤以及这种细胞因子在其他癌症中的潜在失调有关。然后，我们将扩大我们的重点，利用从微阵列和深度测序分析中获得的全基因组数据集，探索潜在的保守逃逸机制。我们预计这些研究可能会揭示控制消息命运的新途径，以及对这些途径的操纵如何导致传染病和遗传病。

DESCRIPTION (provided by applicant): The gammaherpesviruses Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV) are major causes of cancers in immunocompromised individuals. In the case of KSHV, infection rates in sub-Saharan Africa can approach 80% and, as a result, the incidence there of Kaposi's sarcoma is rising and it is emerging as one of the most common adult malignancies. These large double stranded DNA viruses are amplified during lytic replication, but persist for the lifetime of their host in a nonreplicative, latent state. While tumorigenesis is predominantly associated with the latent form of the virus, for KSHV latency is generally not a transforming event and KSHV-induced diseases also require low-level, ongoing lytic replication. Lytic replication is necessary both as a source of new virus to infect naive cells, and to drive production of viral and host paracrine factors that enhance growth of latently infected cells and create an appropriate tumor microenvironment. However, one prominent phenotype occurring during lytic gammaherpesvirus infection is the widespread destruction of cellular messenger RNA (mRNA), which potently inhibits host gene expression. Thus, there is a paradox between the necessity for lytically infected cells to induce specific host genes and the concomitant block in cellular gene expression. The goal of this project is to determine mechanistically how specific host genes evade destruction. Degradation of mRNA during lytic infection is orchestrated by the viral SOX protein, which coordinates with cellular RNA turnover factors to execute shutoff of gene expression. Interestingly, we have observed that select messages such as interleukin-6 (IL-6) are directly refractory to SOX-induced turnover. In the case of IL-6, we have mapped a cis-acting escape element to a region of its 3' untranslated region, and identified several host proteins that complex with this RNA element. One aspect of the project is therefore to explore the mechanistic consequences of these RNA-protein interactions, and determine how they influence IL-6 mRNA stability in the presence and absence of SOX. Given the numerous roles for IL-6 in human disease, this information will be relevant both to KSHV-induced neoplasms as well as potential dysregulation of this cytokine in other cancers. We will then broaden our focus to explore potentially conserved mechanisms of escape, using genome-wide data sets obtained from microarray and deep sequencing analyses. We anticipate these studies may reveal novel pathways that control message fate, and how manipulation of such pathways contributes to both infectious and genetic diseases.