Mechanisms of KSHV posttranscriptional gene regulation

卡波西肉瘤相关疱疹病毒(KSHV)是一种致癌病毒，主要在免疫功能低下的患者中引起卡波西肉瘤和淋巴增生性疾病。像所有疱疹病毒一样，KSHV在潜伏期和裂解期利用宿主基因表达机制仔细控制病毒mRNAs的时间和丰度。虽然人们一直强调转录调控，但最近的报告表明，KSHV和宿主RNA质量控制(QC)途径之间存在两种截然不同的相互作用，它们会降解核转录产物。本研究的目的是明确宿主核RNA、QC通路和KSHV基因表达界面的分子机制。这些目标将定义KSHV用来保护或利用宿主RNA衰退途径的机制。此外，一些宿主途径仍然知之甚少，因此将利用病毒机制来揭示人类分子生物学的基本方面。在这里研究的一条途径中，宿主RNA QC机制针对病毒转录产物进行核衰变。为了保护其RNA，KSHV ORF57蛋白可能通过其他宿主因素抑制这一途径，包括一种名为ALYREF的RNA结合蛋白。在当前提案的目标1和2中，ORF57介导的保护机制和特定宿主因子靶向的RNA将在分子细节上确定。有趣的是，ALYREF和其他ORF57结合蛋白是宿主mRNA输出因子。在目标3中，将在宿主RNA上测试它们在病毒RNA稳定性中的拟议作用，以确定它们是否反映了这些蛋白质的一般活性。除了对腐烂的保护外，KSHV还被报道利用PABPN1-PAPRNA介导的α/γ衰变(PPD)途径来控制晚期基因的时间表达。本提案的目的4旨在确定PPD介导的病毒基因表达调控的机制，并更好地定义PPD途径的组成部分。综上所述，建议的KSHV研究将探讨核RNA QC通路中涉及的分子机制，以更好地了解人类病原体KSHV及其宿主细胞的基本基因表达机制。

Kaposi’s sarcoma-associated herpesvirus (KSHV) is an oncogenic virus that causes Kaposi’s sarcoma and lymphoproliferative diseases primarily in immunocompromised patients. Like all herpesviruses, KSHV uses the host gene expression machinery to carefully control the timing and abundance of viral mRNAs in its latent and lytic phases. While emphasis has been placed on transcriptional control, recent reports suggest two distinct interactions between KSHV and host RNA quality control (QC) pathways that degrade nuclear transcripts. The goal of this proposal is to define the molecular mechanisms at the interface of host nuclear RNA QC pathways and KSHV gene expression. The aims will define mechanisms that KSHV uses to protect from or exploit host RNA decay pathways. In addition, some of the host pathways remain poorly understood, so the viral mechanisms will be harnessed to uncover fundamental aspects of human molecular biology. In one pathway studied here, the host RNA QC machinery targets viral transcripts for nuclear decay. To protect its RNAs, the KSHV ORF57 protein counters that pathway likely through other host factors including an RNA-binding protein called ALYREF. In Aims 1 and 2 of the current proposal, the mechanisms of ORF57-mediated protection and the RNAs targeted by specific host factors will be determined in molecular detail. Interestingly, ALYREF and other ORF57 binding proteins are host mRNA export factors. In Aim 3, their proposed roles in viral RNA stability will be tested on host RNAs to determine whether they reflect a general activity of these proteins. In addition to protection from decay, KSHV has been reported to exploit the PABPN1-PAPα/γ mediated RNA decay (PPD) pathway to control temporal expression of late genes. Aim 4 of the current proposal seeks to define the mechanisms of PPD- mediated regulation of viral gene expression and to better define the components of the PPD pathway. Taken together, the proposed KSHV studies investigate the molecular mechanisms involved in nuclear RNA QC pathways to better understand the basic gene expression mechanisms of the human pathogen KSHV and its human host cell.