Deciphering the Role of CPSF6 in HIV Infection

项目概要 切割和聚腺苷酸化特异性因子 6 (CPSF6) 是一种招募到传入病毒核心的 HIV 宿主因子 在生命周期的早期阶段。 HIV 衣壳 (CA) 和 CPSF6 之间的相互作用已知决定 核易位的细胞决定因素并影响整合位点偏好，但其影响 总体病毒感染性尚不清楚。虽然细胞质 CPSF6 的过度表达已被证明可以限制病毒 据报道，CPSF6 的复制、敲除或 CA-CPSF6 相互作用的破坏具有广泛的影响。 感染性表型的范围。最近，我们实验室发现原代CD4 T细胞中CPSF6的敲除 显着增加 HIV 复制，同时对细胞活力的影响最小。这种复制的增加与 干扰素刺激基因的诱导减少，与之前的报道相反，CPSF6 的作用是 保护病毒免受免疫识别。在本提案中，我们正在测试 CPSF6 的总体假设 在调节 HIV 感染的先天免疫反应中发挥着关键作用，并且该病毒招募 CPSF6 部分是为了规避这种回应。这一假设将在三个目标上进行检验，这些目标广泛地寻求理解 CPSF6 缺失抑制感染免疫反应的机制、HIV 感染的影响 CPSF6 功能，以及 CPSF6 调控途径在控制感染中的潜在作用。在目标 1 中，我们 将检验以下假设：CPSF6 的缺失会通过诱导 替代多聚腺苷酸化 (APA) 或通过增强亲环蛋白 A (CYPA) 的招募来间接 保护核心免受抗病毒因子 TRIM5 的限制。 CPSF6 通常充当 CFIm 的成员 切割因子复合物将聚腺苷酸化引导至 3' 非翻译区 (UTR) 的远端位点。抑制 CFIm 活性会触发 APA，此前已认为 APA 与先天免疫的调节有关 反应，并可以解释观察到的表型。或者，有证据表明 CPSF6 和 CYPA 竞争核心结合，CYPA 结合的丧失先前已被认为与增强的限制有关 和先天的感觉。在目标 2 中，我们将测试以下假设：通过传入病毒核心招募 CPSF6 可以 改变整体 CFIm 功能并诱导 APA。不管这是否与免疫反应的抑制有关 如上所述，众所周知，其他病毒劫持 APA 途径以增强其复制，尽管这 HIV 感染期间尚未进行过研究。最后，在目标 3 中，我们将检验以下假设： CPSF6调节网络可以控制病毒感染性和对感染的免疫反应。 CPSF6 活性为 受翻译后修饰和核质穿梭的调节。 CPSF6 的截短突变体 强制细胞质定位已被证明可以限制 HIV 感染，我们将测试是否可以模仿 其内源性调节机制的遗传和/或化学扰动的影响。总而言之，这部作品 探索了一种新描述的众所周知的 HIV 宿主因子 CPSF6 的表型，并寻求提供更好的 了解病毒通过转录后调节操纵先天免疫反应。

PROJECT SUMMARY Cleavage and polyadenylation specificity factor 6 (CPSF6) is an HIV host factor recruited to incoming viral cores during the early stage of the lifecycle. The interaction between HIV capsid (CA) and CPSF6 is known to dictate the cellular determinants of nuclear translocation and influence integration site preference, but its impact on overall viral infectivity is unclear. While overexpression of cytoplasmic CPSF6 has been shown to restrict viral replication, knock-down of CPSF6 or disruption of the CA-CPSF6 interaction has been reported to have a broad range of infectivity phenotypes. Recently, our lab found that knock-out of CPSF6 in primary CD4+ T cells dramatically increases HIV replication with minimal impact on cell viability. This increase in replication correlates with decreased induction of interferon-stimulated genes, contrary to prior reports that suggest CPSF6 acts to shield the virus from immune recognition. In this proposal, we are testing the overall hypothesis that CPSF6 plays a critical role in regulating the innate immune response to HIV infection and that the virus recruits CPSF6 in part to circumvent this response. This hypothesis will be tested in three aims that broadly seek to understand the mechanism by which loss of CPSF6 dampens the immune response to infection, the impact of HIV infection on CPSF6 function, and the potential role of CPSF6 regulatory pathways in controlling infection. In Aim 1, we will test the hypothesis that loss of CPSF6 acts to dampen the immune response directly by induction of alternative polyadenylation (APA) or indirectly by allowing enhanced recruitment of Cyclophilin A (CYPA) to protect the core from restriction by the antiviral factor TRIM5. CPSF6 normally acts as a member of the CFIm cleavage factor complex to direct polyadenylation to distal sites of the 3' untranslated region (UTR). Inhibition of CFIm activity triggers APA, which has been previously implicated in the regulation of the innate immune response, and could explain the observed phenotype. Alternatively, there is evidence to suggest that CPSF6 and CYPA compete for core binding and loss of CYPA binding has been previously linked to enhanced restriction and innate sensing. In Aim 2, we will test the hypothesis that CPSF6 recruitment by incoming viral cores can alter overall CFIm function and induce APA. Regardless if this is linked to dampening of the immune response above, it is well established that other viruses hijack the APA pathway to enhance their replication, though this hasn't been explored during HIV infection. Finally, in Aim 3, we will test the hypothesis that perturbation of the CPSF6 regulatory network can control viral infectivity and the immune response to infection. CPSF6 activity is regulated by post-translational modification and nuclear-cytoplasmic shuttling. Truncation mutants of CPSF6 that force cytoplasmic localization have been shown to restrict HIV infection, and we will test if we can mimic that effect by genetic and/or chemical perturbation of its endogenous regulatory mechanisms. Altogether, this work explores a newly described phenotype for a well-known HIV host factor, CPSF6, and seeks to provide a better understanding of viral manipulation of the innate immune response by post-transcriptional regulation.