HARC Center: HIV Accessory and Regulatory Complexes

我们对Vif的目标集中在CBFp的作用、宿主复合物修饰和Vif相互作用的生物学上 新的合作伙伴。我们的研究将不仅为Vif-宿主相互作用建立新的范式， 也更普遍地用于参与泛素-蛋白酶体系统的限制因子。我们的蛋白质组 研究确定了其他Vif伙伴，包括与自噬有关的AMRA 1和SQSTM，以及 与转录辅阻遏物复合物NCOR 1/HDAC 3/GPS 2/TBL 1 R [2]。根据这些发现， 将潜在地定义维生素的未预料到的替代作用，例如调节染色体基因表达， 在HIV发病机制中。 Vif是一种非常重要的蛋白质。它对HIV的传播至关重要，是一种保守的病毒， 对抗宿主限制因素的策略。Vif触发AP 0 BEC 3（A3）成员的降解 胞嘧啶脱氨酶家族，否则通过引起致命的超突变来阻止病毒HIV复制。 病毒基因组[6，7]。Vif劫持了细胞Cullin-RING泛素E3连接酶（CRL），该酶作用于细胞凋亡的最后一步。 三酶，E1-E2-E3级联，以促进A3底物的泛素化和随后的降解[8- 10]。 1.0]。Vif E3连接酶由CUL 5/RBX 2支架和底物衔接子、延伸蛋白B和C（延伸蛋白BC）组成。 BMPBC结合约50种不同的细胞因子信号转导抑制因子（SOCS）蛋白，这些蛋白具有底物特异性 CRL 5的因素[11，12]。SOCS蛋白含有一个三螺旋基序（SOCS盒）， CUL 5，分别[13，14]。Vif的C-末端作为细胞SOCS蛋白的分子模拟物[15，16]， 对功能重要的Vif的其他区域已经被绘制出来[17-19]。重要的是我们 将CBFp确定为稳定维生素以结合CRL 5机器并触发A3 G所需的关键宿主因子 退化[1，2]。 CRL 5还需要NEDD 8为Vif进行修改以抵消A3 G [10]。CRL的NEDD 8化需要 E1-E2-E3级联非常类似于泛素[20]。NEDD 8修改耦合到NEDD E3（DCN~ Cullin Neddylation缺陷）蛋白，其通过乙酰化将CRL与NEDD 8 E2桥接， 通过CRL磷酸化拮抗[21-25]，一种有效的基于机制的NEDD 8 El抑制剂（MLN 4924）在 用于治疗血液系统癌症的I期临床试验[26，27]，强调了NEDD 8在 控制细胞蛋白质的稳态。这些观察结果提示了一种新的抗逆转录病毒策略， 干扰宿主NEDD 8通路或PTM可以抑制CRL功能并恢复先天免疫 由限制因素提供。

Our aims for Vif focus on the roles of CBFp, host complex modifications, and the biology of Vif interactions with newly identified partners. Our studies will establish new paradigms not only for Vif-host interactions, but also more generally for restriction factors that engage the ubiquitin-proteasome system. Our proteomics studies identified additional Vif partners, including AMRA1 and SQSTM implicated in autophagy, as well as with the transcriptional corepressor complex NCOR1/HDAC3/GPS2/TBL1R [2]. Following up these discoveries will potentially define unanticipated alternative roles for Vit such as regulating chromosomal gene expression, in HIV pathogenesis. Vif is a highly significant protein. It is essential for the spread of HIV and represents a conserved viral strategy for counteracting host restriction factors. Vif triggers degradation of members of the AP0BEC3 (A3) family of cytosine deaminases that otherwise halt viral HIV replication by causing lethal hypermutation of the viral genome [6, 7]. Vif hijacks a cellular Cullin-RING ubiquitin E3 ligase (CRL) that acts in the last step of a three-enzyme, E1-E2-E3 cascade to promote ubiquitination and subsequent degradation of A3 substrates [8- 1.0]. The Vif E3 ligase consists ofthe CUL5/RBX2 scaffold and substrate adaptors, Elongins B and C (ELOBC). ELOBC binds ~50 different Suppressor of Cytokine Signaling (SOCS) proteins, which are substrate specificity factors for CRL5 [11, 12]. SOCS proteins contain a three-helix motif (the SOCS box) that engages ELOC and CUL5, respectively [13, 14]. The C-terminus of Vif acts as a molecular mimic of cellular SOCS proteins [15,16], and additional regions of Vif that are important for function have been mapped [17-19]. Importantly, we identified CBFp as a critical host factor needed to stabilize Vit to bind the CRL5 machinery and trigger A3G degradation [1, 2]. CRL5 also requires modification by NEDD8 for Vif to counteract A3G [10]. NEDD8ylation of CRLs requires an E1-E2-E3 cascade much like ubiqultin [20]. The NEDD8 modification is coupled to NEDD E3 (DCN~ Defective in Cullin Neddylation) proteins, which bridge CRL with NEDD8 E2 via acetylation and may be antagonized by CRL phosphorylation [21-25], A potent, mechanism-based NEDD8 El inhibitor (MLN4924) is in Phase 1 clinical trials for treatment of hematologic cancers [26, 27], underscoring the role of NEDD8 in controlling cellular protein homeostasis. These observations suggest a novel antiretroviral strategy in which perturbing host NEDD8 pathways or PTMs could suppress CRL function and restore the innate immunity provided by restriction factors.