Roles of NELF on HIV replication and viral latency

描述(申请人提供)：高效抗逆转录病毒疗法(HAART)已被证明在许多情况下通过将血浆病毒水平降低到低于可检测的限度而显著降低因艾滋病毒-L感染而导致的发病率和死亡率。然而，最近的研究表明，在接受HAART的患者中，仍有一小部分静息的CD4+T细胞含有可诱导的、具有复制能力的前病毒。这一潜伏的HIV-1宿主为成功根除该病毒制造了障碍。以前的观察表明，在潜伏感染的细胞中，HIV转录主要在伸长阶段受阻，该阶段受宿主细胞转录因子和病毒蛋白Tat的正负调节。我们已经证明，一种细胞蛋白复合体，负延伸因子(NELF)以病毒特异性的方式被招募到HIV-1启动子。在TAT和正延伸因子13(P-TEF[3)的存在和不存在的情况下，该复合体的RD亚基直接与HIV-L TAR结合，而P-TEFI3的激酶活性使RD的磷酸化取消了与TAR的这种相互作用。NELF与TAR结合导致HIV-1转录受阻，这可能是从HAART反应者来源的潜伏感染的PBMC中观察到以短启动子近端转录为主的各种检测方法检测到的原因。因此，NELF可能是HIV-1从非生产性转录向生产性转录转变的关键角色之一。我们假设NELF是潜伏感染细胞中HIV转录水平低的一个因素。在这项拟议的研究中，我们将使用新开发的siRNA技术和在模型细胞系中的高灵敏度分析，以及从HIV-1感染患者收集的PBMC，来确定NELF在TAT依赖和TAT非依赖转录中的确切作用。此外，我们将试图通过调节NELF的活性来激活潜伏感染细胞中的病毒转录，希望开发出潜在的治疗方法来减少或消除这种潜伏的蓄水池。这项研究的结果将增加我们对HW-1发病机制的理解，并可能为新的治疗方向提供建议。

DESCRIPTION (provided by applicant): Highly active antiretroviral therapy (HAART) has been shown to significantly lower morbidity and mortality rates from HIV-l infection by reducing levels of plasma virus to below detectable limits in many instances. However, recent studies indicate that there remains a small population of resting CD4+ T cells containing inducible, replication competent provirus in patients receiving HAART for extended periods of time. This latent HIV-1 reservoir creates an obstacle for the successful eradication of the virus. Previous observations suggest that in latently infected cells HIV transcription is blocked mainly at the elongation step, which is regulated positively and negatively by host cellular transcription factors and the viral protein Tat. We have demonstrated that a cellular protein complex, negative elongation factor (NELF) is recruited to the HIV-1 promoter in a virus specific manner. The RD subunit of this complex binds directly to HIV-l TAR in the presence and absence of Tat and the positive elongation factor 13(P-TEF[3), and phosphorylation of RD by the kinase activity of P-TEFI 3 abolishes this interaction with TAR. The block to productive HIV-1 transcription caused by the binding of NELF to TAR may indicate a reason for the detection of predominantly short, promoter proximal transcripts by various assays observed in the latently infected PBMCs derived from HAART responders. Therefore NELF may be one of the key players involved in the transition from nonproductive to productive HIV-1 transcription. We hypothesize that NELF is a factor contributing to the low level of HIV transcription in latently infected cells. In this proposed study, we will define the precise roles of NELF in Tat-dependent and Tat-independent transcription using a newly developed siRNA technology and a highly sensitive assay in a model cell line, as wells as PBMCs collected from HIV-1 infected patients. Moreover, we will attempt to activate viral transcription in latently infected cells by regulating NELF activity in hopes of developing potential treatments to reduce or abolish this latent reservoir. The results obtained from this study will increase our understanding of HW-1 pathogenesis and may suggest new therapeutic directions.