Role of DNA sensors in host anti-retroviral defense

逆转录病毒是动物和人类疾病的主要原因。逆转录病毒反向复制 使用病毒编码的转录酶将病毒RNA转录成DNA。由于未涂覆以及反涂 转录发生在细胞质中，宿主有可能识别“外来”的病毒RNA或DNA 传感器。最近，包括cGAS、DDX41和ALR IFI16在内的一些主机传感器已经 与胞浆DNA的识别有关。使用突变的小鼠白血病病毒(MLV)与不稳定的 衣壳蛋白诱导强烈的干扰素β反应，我们发现逆转录本诱导了这种反应 在小鼠身上鉴定出识别所需的三种传感器--IFI203、DDX41和cGAS--通过刺痛发出信号 通过APOBEC3基因敲除和刺痛突变小鼠和细胞，我们展示了导致干扰素增加的途径 宿主逆转录病毒限制因子APOBEC3限制了触发胞浆的逆转录水平 感官。此外，我们还发现，体内核酸传感的作用是增加干扰素-1的表达。 受调控的限制因子，如APOBEC3，进而降低病毒载量。 虽然识别涉及识别的传感器是重要的第一步，但到目前为止还有许多 悬而未决的问题。虽然我们和其他人已经证明了对逆转录病毒核酸的宿主感知是 依赖于逆转录，因此必须包括DNA检测，参与的至少3 对感染反应的不同因素可能意味着RNA或RNA/DNA也被识别。 此外，虽然人们普遍认为DNA结合的cGAS激活了环状GMP-AMP的产生，而且 该配体进而激活STING，无论IFI203和DDX41在相同还是平行的途径上工作 诱导干扰素的作用尚不清楚。最后，不同宿主传感器在控制病毒中的相对重要性 体内感染尚不清楚。 为了解决这些问题，我们建议实现以下目标： 哪些逆转录病毒核酸作为cGAS、IFI203和DDX41的配体？ 在体内控制感染的过程中，每个传感器扮演什么角色？ CGAS、IFI203和DDX41在逆转录病毒感染应答中的作用途径是什么？ 了解宿主对逆转录病毒感染的初始反应对于我们确定如何 这些病毒建立了持续感染，以及发现了干预这些病毒的新方法 感染。使用功能和遗传方法的组合，这一提议将描绘出分子 逆转录病毒核酸被细胞感知的方式，以及确定这一点的意义 体内感染和发病机制的传感。

Retroviruses are major causes of disease in animals and humans. Retroviruses replicate by reverse transcribing viral RNA into DNA, using the virus-encoded transcriptase. Since uncoating as well as reverse transcription occur in the cytoplasm, there is the potential for recognition of “foreign” viral RNA or DNA by host sensors. Recently, a number of host sensors, including cGAS, DDX41 and the ALR IFI16, have been implicated in the recognition of cytosolic DNA. Using a mutant murine leukemia virus (MLV) with an unstable capsid that induces a strong IFNβ response, we found that reverse transcripts induced this response and identified three sensors in mice required for recognition – IFI203, DDX41 and cGAS - that signal via the STING pathway leading to increased IFN Using APOBEC3 knockout and STING mutant mice and cells, we showed that the host retroviral restriction factor APOBEC3 limits the levels of reverse transcripts that trigger cytosolic sensing. Moreover, we found that the role of nucleic acid sensing in vivo is to increased expression of IFN- regulated restriction factors like APOBEC3 that in turn reduce viral load. While the identification of sensors involved in recognition is an important first step, there as of yet many unanswered questions. While we and others have shown that host sensing of retroviral nucleic acid is dependent on reverse transcription and therefore must include DNA detection, the involvement of at least 3 different factors in the response to infection could mean that RNA or RNA/DNA are also recognized. Additionally, while it is well-accepted that DNA binding cGAS activates production of cyclic GMP-AMP and that this ligand in turn activates STING, whether IFI203 and DDX41 operate in the same or parallel pathways to induce IFN is not known. Finally, the relative importance of the different host sensors in controlling viral infection in vivo has yet to be elucidated. To address these questions, we propose to carry out the following aims: I. What retroviral nucleic acids serve as ligands for cGAS, IFI203 and DDX41? II. What role does each of the sensors play in in vivo control of infection? III. What is the pathway of action of cGAS, IFI203 and DDX41 in the response to retroviral infection? Understanding the initial host response to infection by retroviruses is critical to our ability to determine how these viruses establish persistent infection as well the discovery of novel approaches to intervene in these infections. Using a combination of functional and genetic approaches, this proposal will delineate the molecular means by which retroviral nucleic acids are sensed by cells, as well as to determine the significance of this sensing in in vivo infection and pathogenesis.