Department of Cellular and Molecular Pharmacology, University of California-San Francisco, San Francisco, California 94158, USA.
Nature. 2011 Dec 21;481(7381):371-5. doi: 10.1038/nature10693.
Restriction factors, such as the retroviral complementary DNA deaminase APOBEC3G, are cellular proteins that dominantly block virus replication. The AIDS virus, human immunodeficiency virus type 1 (HIV-1), produces the accessory factor Vif, which counteracts the host's antiviral defence by hijacking a ubiquitin ligase complex, containing CUL5, ELOC, ELOB and a RING-box protein, and targeting APOBEC3G for degradation. Here we reveal, using an affinity tag/purification mass spectrometry approach, that Vif additionally recruits the transcription cofactor CBF-β to this ubiquitin ligase complex. CBF-β, which normally functions in concert with RUNX DNA binding proteins, allows the reconstitution of a recombinant six-protein assembly that elicits specific polyubiquitination activity with APOBEC3G, but not the related deaminase APOBEC3A. Using RNA knockdown and genetic complementation studies, we also demonstrate that CBF-β is required for Vif-mediated degradation of APOBEC3G and therefore for preserving HIV-1 infectivity. Finally, simian immunodeficiency virus (SIV) Vif also binds to and requires CBF-β to degrade rhesus macaque APOBEC3G, indicating functional conservation. Methods of disrupting the CBF-β-Vif interaction might enable HIV-1 restriction and provide a supplement to current antiviral therapies that primarily target viral proteins.
限制因子，如逆转录病毒互补 DNA 脱氨酶 APOBEC3G，是细胞蛋白，它们主要阻止病毒复制。艾滋病病毒，即人类免疫缺陷病毒 1 型（HIV-1），产生辅助因子 Vif，通过劫持含有 CUL5、ELOC、ELOB 和一个 RING 盒蛋白的泛素连接酶复合物，靶向 APOBEC3G 进行降解，从而抵消宿主的抗病毒防御。在这里，我们使用亲和标签/纯化质谱方法揭示，Vif 还将转录共因子 CBF-β募集到这个泛素连接酶复合物中。CBF-β 通常与 RUNX DNA 结合蛋白协同作用，允许重组六蛋白组装的重建，引发与 APOBEC3G 特异性多泛素化活性，但不与相关脱氨酶 APOBEC3A 发生反应。通过 RNA 敲低和遗传互补研究，我们还证明 CBF-β 是 Vif 介导的 APOBEC3G 降解所必需的，因此也是维持 HIV-1 感染性所必需的。最后，猴免疫缺陷病毒（SIV）Vif 也与 CBF-β 结合并需要 CBF-β 来降解恒河猴 APOBEC3G，表明功能保守。破坏 CBF-β-Vif 相互作用的方法可能会使 HIV-1 受到限制，并为目前主要针对病毒蛋白的抗病毒治疗提供补充。
