BTB-BACK Domain Protein POB1 Suppresses Immune Cell Death by Targeting Ubiquitin E3 ligase PUB17 for Degradation.
BTB-BACK Domain Protein POB1 Suppresses Immune Cell Death by Targeting Ubiquitin E3 ligase PUB17 for Degradation.
复制标题
BTB背域蛋白POB1通过靶向泛素E3连接酶Pub17抑制免疫细胞死亡。
DOI：
10.1371/journal.pgen.1006540
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发表时间：
2017-01
期刊：
影响因子：
4.5
通讯作者：
Sadanandom A
中科院分区：
文献类型：
--
作者：
Orosa B;He Q;Mesmar J;Gilroy EM;McLellan H;Yang C;Craig A;Bailey M;Zhang C;Moore JD;Boevink PC;Tian Z;Birch PR;Sadanandom A
过敏性反应程序性细胞死亡(HR-PCD)是植物免疫中的一个重要特征，是限制病原菌和防止疾病发展所必需的。对这一过程的精确控制对细胞存活和有效的免疫反应至关重要。发现具有抑制HR-PCD功能的新成分将有助于理解这一基本机制的调节。在这里，我们报告了BTB结构域E3连接酶蛋白POB1的鉴定和特性，该蛋白具有抑制由进化上不同的病原体触发的HR-PCD的功能。POB1活性降低的烟草和烟草植株表现出加速的HR-PCD，而POB1水平升高的烟草表现出减弱的HR-PCD。我们证明POB1的二聚化和核定位对于其抑制HR-PCD的功能至关重要。通过蛋白质-蛋白质相互作用分析，我们确定植物U-Box E3连接酶PUB17是POB1介导的蛋白酶体降解的靶标。PUB17是植物天然免疫的正性调节因子。利用共聚焦成像和平面免疫沉淀分析，我们发现POB1与PUB17在细胞核内相互作用，并刺激其降解。与PUB17相互作用减弱的POB1突变版本不能抑制HR-PCD，这表明POB1介导的PUB17 U-box E3连接酶的降解是植物特定免疫途径负调控的重要步骤。我们的数据揭示了BTB结构域蛋白在植物天然免疫反应中抑制HR-PCD的新机制。控制植物中的PCD，如动物中的PCD，是决定对疾病的易感性或抵抗力的核心。然而，对于决定PCD在植物免疫反应过程中如何协调的生化过程，人们确实缺乏了解。在这里，我们证明了BTB结构域蛋白POB1是一种保守的新的负调节因子，由进化上不同的病原体触发的植物免疫反应。BTB结构域蛋白与Cullin-3蛋白结合形成泛素E3连接酶。我们发现，U-Box E3连接酶PUB17是泛素E3连接酶POB1降解的靶标，它是植物多条免疫途径中公认的正向调节因子。我们还证明了这种定向的蛋白分解发生在植物细胞的细胞核中。在这份报告中，我们提供了明确的证据，区分了BTB结构域依赖的二聚化和Cullin-3泛素连接酶组装，并将其与植物免疫信号的靶标降解联系起来。
Hypersensitive response programmed cell death (HR-PCD) is a critical feature in plant immunity required for pathogen restriction and prevention of disease development. The precise control of this process is paramount to cell survival and an effective immune response. The discovery of new components that function to suppress HR-PCD will be instrumental in understanding the regulation of this fundamental mechanism. Here we report the identification and characterisation of a BTB domain E3 ligase protein, POB1, that functions to suppress HR-PCD triggered by evolutionarily diverse pathogens. Nicotiana benthamiana and tobacco plants with reduced POB1 activity show accelerated HR-PCD whilst those with increased POB1 levels show attenuated HR-PCD. We demonstrate that POB1 dimerization and nuclear localization are vital for its function in HR-PCD suppression. Using protein-protein interaction assays, we identify the Plant U-Box E3 ligase PUB17, a well established positive regulator of plant innate immunity, as a target for POB1-mediated proteasomal degradation. Using confocal imaging and in planta immunoprecipitation assays we show that POB1 interacts with PUB17 in the nucleus and stimulates its degradation. Mutated versions of POB1 that show reduced interaction with PUB17 fail to suppress HR-PCD, indicating that POB1-mediated degradation of PUB17 U-box E3 ligase is an important step for negative regulation of specific immune pathways in plants. Our data reveals a new mechanism for BTB domain proteins in suppressing HR-PCD in plant innate immune responses. Control over PCD in plants, like in animals, is central to determining susceptibility or resistance to disease. Yet there is a real paucity in understanding of the biochemical processes that are crucial in determining how PCD is co-ordinated during plant immune responses. Here we demonstrate that a BTB domain protein, POB1, is a conserved novel negative regulator of plant immune responses triggered by evolutionarily diverse pathogens. BTB domain proteins have been shown to associate with Cullin-3 proteins to form ubiquitin E3 ligases. We reveal that the U-Box E3 ligase PUB17, a well-established positive regulator of multiple immune pathways in plants, is a target for degradation by the ubiquitin E3 ligase POB1. We also demonstrate that this targeted proteolysis occurs in the nuclei of plant cells. In this report we provide clear evidence that distinguishes between BTB domain dependant dimerization and Cullin-3 ubiquitin ligase assembly and link this to target degradation in plant immune signalling.