Characterization of the antiviral activity of BCA2

描述（由申请人提供）：BCA2（乳腺癌相关基因2，也称为RNF115， ZNF364或Rabring7）是一种环指E3泛素连接酶，在大多数乳腺癌细胞系中响应雌激素而上调。最近的一项研究表明，BCA2与tetherin的细胞质结构域相互作用，促进拴系HIV-1颗粒的内化和溶酶体降解，并且BCA2的E3连接酶活性对于增强tetherin介导的HIV-1限制是必不可少的。因此，BCA2可能作为tetherin辅助因子，在不表达tetherin的细胞中缺乏抗病毒活性。然而，在这里，我们首次表明，BCA2通过降低HIV-1 Gag的细胞水平，以一种不依赖于系链蛋白的方式抑制病毒的产生，并且这种活性需要一个完整的无名指结构域。此外，我们发现BCA2物理上与Gag相互作用并促进其泛素化和溶酶体降解，这表明BCA2可能是一种干扰病毒组装的先天抗病毒因子。我们希望通过描述BCA2抗病毒活性的分子机制（Specific Aim 1）和识别参与BCA2活性调节的分子以及响应BCA2而激活的细胞途径（Specific Aim 2）来正式解决这一假设。更好地了解限制病毒产生的先天机制将有助于研制抗逆转录病毒药物，以遏制病毒在受影响个体中的复制。因此，这里概述的目标与确定抗逆转录病毒治疗控制HIV-1感染的新靶点直接相关。

DESCRIPTION (provided by applicant): BCA2 (Breast Cancer-Associated gene 2, also known as RNF115, ZNF364 or Rabring7) is a RING-finger E3 ubiquitin ligase that is up-regulated in most breast cancer cell lines in response to estrogen. A recent study showed that BCA2 interacts with the cytoplasmic domain of tetherin to promote the internalization and lysosomal degradation of tethered HIV-1 particles, and that the E3 ligase activity of BCA2 is dispensable to enhance the tetherin-mediated restriction of HIV-1. Therefore, BCA2 would act as a tetherin co-factor, lacking antiviral activity in cells that do not express tetherin. However, here we show, fo the first time, that BCA2 inhibits virus production in a tetherin-independent manner by reducing the cellular levels of HIV-1 Gag, and that this activity requires an intact RING-finger domain. Furthermore, we show that BCA2 physically interacts with Gag and promotes its ubiquitination and lysosomal degradation, suggesting that BCA2 may be an innate antiviral factor that interferes with virus assembly. We want to formally address this hypothesis by characterizing the molecular mechanisms of the antiviral activity of BCA2 (Specific Aim 1) and by identifying the molecules that participate in the regulation of BCA2's activity, as well as the cellular pathways that are activated in response to BCA2 (Specific Aim 2). A better understanding of the innate mechanisms that limit virus production will help in the elaboration of antiretroviral drugs o contain virus replication in affected individuals. Therefore, the objectives outlined here are directly relevant to identifying new targets for antiretroviral therapy to control HIV-1 infection.