Dual Mechanisms for APOBEC3 Suppression by HIV-1 Vif

 描述（由申请人提供）：HIV-1和几乎所有其他慢病毒编码一种称为病毒感染因子（Vif）的辅助蛋白，该蛋白是体内病毒有效复制和发病所需的。Vif的典型功能是通过E3泛素连接酶复合物触发细胞APOBEC 3（A3）蛋白的多聚泛素化和降解来克服其限制。我们最近确定了转录因子CBF 3作为一个Vif辅因子所需的装配和功能的E3泛素连接酶复合物。CBF在CD 4 + T细胞中表达，并通过与DNA结合RUNX转录因子异二聚化来调节参与T细胞发育和免疫功能的基因的表达。我的初步敲除和敲除实验表明，CBF β是T细胞中A3转录的正调节因子。抑制CBF 3功能抑制A3基因转录并导致Vif缺陷型HIV-1感染性的伴随增加。我假设CBF 3/RUNX复合物直接刺激A3基因转录，Vif通过劫持CBF 3形成Vif/CBF 3 E3泛素连接酶复合物降解A3蛋白来破坏这一过程。因此，Vif有效地将两种独立且高度互补的机制偶联以抑制A3抗病毒活性。这里提出的研究将测试这一潜在的范式转变假设，并可以为为什么Vif劫持CBF 3而不是任何其他细胞蛋白质提供一个优雅的进化合理化。

 DESCRIPTION (provided by applicant): HIV-1 and nearly all other lentiviruses encode an accessory protein termed viral infectivity factor (Vif) that is required for productive viral replication and pathogenesis in vivo. Vif functions canonically to overcome restriction by the cellular APOBEC3 (A3) proteins by triggering their polyubiquitination and degradation through an E3 ubiquitin ligase complex. We recently identified the transcription factor CBFß as a Vif cofactor required for the assembly and function of this E3 ubiquitin ligase complex. CBFß is expressed in CD4+ T cells and functions by heterodimerizing with the DNA binding RUNX transcription factors to regulate expression of genes involved in T cell development and immune function. My preliminary knockdown and knockout experiments indicate that CBFß is a positive regulator of A3 transcription in T cells. Ablating CBFß function suppresses A3 gene transcription and causes a concomitant increase in Vif-deficient HIV-1 infectivity. I hypothesize that CBFß/RUNX complexes directly stimulate A3 gene transcription and that Vif disrupts this process by hijacking CBFß to form the Vif/CBFß E3 ubiquitin ligase complex that degrades A3 proteins. Thus, Vif efficiently couples two independent and highly complementary mechanisms to suppress A3 antiviral activity. The studies proposed here will test this potentially paradigm-shifting hypothesis, and could provide an elegant evolutionary rationalization for why Vif hijacks CBFß as opposed to any other cellular protein.