Mehle Andrew, Thomas Elaine R, Rajendran Kottampatty S, Gabuzda Dana
Department of Cancer Immunology and AIDS, Dana Farber Cancer Institute, Boston, Massachusetts 02115; Departments of Pathology, Harvard Medical School, Boston, Massachusetts 02115.
Department of Cancer Immunology and AIDS, Dana Farber Cancer Institute, Boston, Massachusetts 02115; Departments of Neurology, Harvard Medical School, Boston, Massachusetts 02115.
J Biol Chem. 2006 Jun 23;281(25):17259-17265. doi: 10.1074/jbc.M602413200. Epub 2006 Apr 24.
Human immunodeficiency virus-1 (HIV-1) Vif overcomes the anti-viral activity of APOBEC3G by targeting it for ubiquitination via a Cullin 5-ElonginB-ElonginC (Cul5-EloBC) E3 ligase. Vif associates with Cul5-EloBC through a BC-box motif that binds EloC, but the mechanism by which Vif selectively recruits Cul5 is poorly understood. Here we report that a region of Vif (residues 100-142) upstream of the BC-box binds selectively to Cul5 in the absence of EloC. This region contains a zinc coordination site HX5CX17-18CX3-5H (HCCH), with His/Cys residues at positions 108, 114, 133, and 139 coordinating one zinc ion. The HCCH zinc coordination site, which is conserved among primate lentivirus Vif proteins, does not correspond to any known class of zinc-binding motif. Mutations of His/Cys residues in the HCCH motif impair zinc coordination, Cul5 binding, and APOBEC3G degradation. Mutations of conserved hydrophobic residues (Ile-120, Ala-123, and Leu-124) located between the two Cys residues in the HCCH motif disrupt binding of the zinc-coordinating region to Cul5 and inhibit APOBEC3G degradation. The Vif binding site maps to the first cullin repeat in the N terminus of Cul5. These data suggest that the zinc-binding region in Vif is a novel cullin interaction domain that mediates selective binding to Cul5. We propose that the HCCH zinc-binding motif facilitates Vif-Cul5 binding by playing a structural role in positioning hydrophobic residues for direct contact with Cul5.
人类免疫缺陷病毒1型（HIV-1）的病毒感染因子（Vif）通过Cullin 5-ElonginB-ElonginC（Cul5-EloBC）E3连接酶将载脂蛋白B mRNA编辑酶催化多肽样3G（APOBEC3G）靶向泛素化，从而克服其抗病毒活性。Vif通过与EloC结合的BC盒基序与Cul5-EloBC缔合，但Vif选择性招募Cul5的机制尚不清楚。在此，我们报告在不存在EloC的情况下，BC盒上游的Vif区域（第100 - 142位氨基酸残基）选择性地与Cul5结合。该区域包含一个锌配位位点HX5CX17 - 18CX3 - 5H（HCCH），第108、114、133和139位的组氨酸/半胱氨酸残基配位一个锌离子。HCCH锌配位位点在灵长类慢病毒Vif蛋白中保守，与任何已知类型的锌结合基序均不对应。HCCH基序中组氨酸/半胱氨酸残基的突变会损害锌配位、Cul5结合及APOBEC3G降解。位于HCCH基序两个半胱氨酸残基之间的保守疏水残基（异亮氨酸-120、丙氨酸-123和亮氨酸-124）的突变会破坏锌配位区域与Cul5的结合并抑制APOBEC3G降解。Vif结合位点定位于Cul5 N端的第一个cullin重复序列。这些数据表明，Vif中的锌结合区域是一个新的cullin相互作用结构域，介导与Cul5的选择性结合。我们提出，HCCH锌结合基序通过在定位疏水残基以与Cul5直接接触中发挥结构作用，促进Vif - Cul5结合。
