HARC Center: HIV Accessory and Regulatory Complexes

我们对Vif的目标集中在CBFp的作用、宿主复杂的修饰和Vif相互作用的生物学上 与新确定的合作伙伴合作。我们的研究不仅将建立Vif-宿主相互作用的新范式，而且将建立Vif-host相互作用的新范式 更一般地，也适用于参与泛素-蛋白酶体系统的限制因素。我们的蛋白质组学 研究发现，包括AMRA1和SQSTM在内的其他VIF伙伴与自噬有关，以及 与转录辅阻遏子复合体NCOR1/HDAC3/GPS2/TBL1R[2]。跟进这些发现 将潜在地为维生素T定义意想不到的替代角色，如调节染色体基因表达， 在HIV的发病机制中。 Vif是一种非常重要的蛋白质。它对艾滋病毒的传播是必不可少的，并代表着一种保守的病毒 对抗寄主限制因素的策略。VIF引发AP0BEC3(A3)成员的降解 胞嘧啶脱氨酶家族，通过引起致命性的超突变来阻止艾滋病毒复制 病毒基因组[6，7]。VIF劫持了一种细胞库林环泛素E3连接酶(CRL)，它在细胞内的最后一步作用 三种酶，E1-E2-E3级联，促进A3底物的泛素化和随后的降解[8- 1.0]。Vif E3连接酶由CUL5/RBX2支架和底物适配器Elongins B和C(ELOBC)组成。 ELOBC结合约50种不同的细胞因子信号转导抑制蛋白，具有底物特异性 CRL5的因素[11，12]。SOCS蛋白包含一个三螺旋基序(SOCS盒)，它与ELOC和 CUL5分别为[13，14]。Vif的C末端作为细胞SoCS蛋白的分子模拟物[15，16]， 并绘制了对功能重要的Vif的附加区域[17-19]。重要的是，我们 确定CBFp是稳定Vit以绑定CRL5机器并触发A3G所需的关键宿主因素 退化[1，2]。 CRL5还需要NEDD8对VIF进行修改，以对抗A3G[10]。CRLS的NEDD8甲基化需要 一个E1-E2-E3级联很像泛素[20]。NEDD8修饰与NEDE3(DCN~)偶联。 通过乙酰化连接CRL和NEDD8 E2的蛋白质，可能是 被CRL磷酸化[21-25]拮抗，一种有效的、基于机制的NEDD8 EL抑制剂(MLN4924)正在 治疗血液病的第一阶段临床试验[26，27]，强调NEDD8在 控制细胞蛋白质动态平衡。这些观察表明了一种新的抗逆转录病毒策略 干扰宿主NEDD8通路或PTMS可以抑制CRL功能，恢复天然免疫 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.