Vpr A Viral Coactivator Of Nuclear Receptors--Mechanisms

Vpr 核受体的病毒共激活剂--机制

• 批准号: 6551117
• 负责人: Tomoshige Kino
• 金额: --
• 依托单位: EUNICE KENNEDY SHRIVER NATIONAL INSTITUTE OF CHILD HEALTH & HUMAN DEVELOPMENT
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6551117
• 关键词: HIV infections; corticosteroid receptors; gene induction /repression; genetically modified animals; glucocorticoids; host organism interaction; human immunodeficiency virus 1; laboratory mouse; mutant; protein structure function; receptor expression; transcription factor; virus genetics; virus protein; virus replication

We have demonstrated that the HIV-1 accessory protein Vpr acts as a potent coactivator of the glucocorticoid receptor (GR), increasing the sensitivity of transfected cells to glucocorticoids by many fold. It accomplishes this by binding to the GR through a coactivator motif LXXLL, by interacting with amino acid 2141-2195 of the cointegrrator p300 -which contains a binding site of p160 nuclear receptor coactivators- functioning as a potentiator of the nuclear receptor coactivator system and several elements of the RNA polymerase II into a ternary transcription/elongation complex. We have demonstrated that the HIV-1 protein Tat stimulates the HIV-1 LTR by participating in a similar ternary complex containing p160 nuclear receptor coactivatorsand Vpr. Indeed, Tat, and its partner protein CyclinT1, bind to N-terminus of p160 coactivators and enhance accumulation of elongation complex p-TEFb to the coactivator complex. Vpr functions as an enhancer of Tat-stimulated HIV-1-LTR and nuclear receptor-governed promoters, functioning as a potentiator of nuclear receptor coactivator system. By modulation of coactivator activites, Vpr may enhance viral replication/proliferation both directly and indirectly. Using a yeast two-hybrid screening, we found that Vpr strongly associates with the 14-3-3 protein, through which Vpr arrests host cell cycle at G2/M phase. Based on the above in vitro evidence, we will proceed to examine the in vivo actions of Vpr in transgenic mice which conditionally express wild type Vpr or two of its mutants that have respectively lost either their GR coactivator or the cell cycle arresting activity; and, (3) the in vivo expression and effects of Vpr in HIV-1-infected humans. The GR coactivator activity of Vpr can explain the immunosuppression, muscular atrophy and lipodystrophic visceral adiposity of patients with AIDS.

我们已经证明，HIV-1 辅助蛋白 Vpr 是糖皮质激素受体 (GR) 的有效共激活剂，可将转染细胞对糖皮质激素的敏感性提高许多倍。它通过共激活子基序 LXXLL 与 GR 结合，通过与共整合子 p300 的氨基酸 2141-2195 相互作用来实现这一点（其中包含 p160 核受体共激活子的结合位点），充当核受体共激活子系统的增强子和多个RNA聚合酶II的元件形成三元转录/延伸复合物。我们已经证明，HIV-1 蛋白 Tat 通过参与包含 p160 核受体共激活剂和 Vpr 的类似三元复合物来刺激 HIV-1 LTR。事实上，Tat 及其伙伴蛋白 CyclinT1 与 p160 共激活剂的 N 末端结合，并增强延伸复合物 p-TEFb 向共激活剂复合物的积累。 Vpr 充当 Tat 刺激的 HIV-1-LTR 的增强子和核受体控制的启动子，充当核受体共激活系统的增强剂。通过调节共激活因子活性，Vpr 可以直接或间接增强病毒复制/增殖。通过酵母双杂交筛选，我们发现 Vpr 与 14-3-3 蛋白密切相关，Vpr 通过该蛋白将宿主细胞周期阻滞在 G2/M 期。基于上述体外证据，我们将继续研究Vpr在转基因小鼠中的体内作用，这些转基因小鼠条件性表达野生型Vpr或其两个突变体，这些突变体分别失去了GR共激活剂或细胞周期阻滞活性； (3) Vpr 在 HIV-1 感染者体内的表达和影响。 Vpr的GR共激活剂活性可以解释艾滋病患者的免疫抑制、肌肉萎缩和脂肪营养不良性内脏肥胖。