Mechanism of atypical ubiquitination and deubiquitination by bacterial effectors

项目总结 宿主功能的主动调节是细菌病原体成功的关键。无所不在的 网络几乎调控着真核生物中的每一个细胞过程，特别是那些参与 检测、识别和应对感染。因此，许多病原体针对宿主泛素化。 为了他们的利益。早期的研究表明，嗜肺军团菌是引起 军团病通过使用至少9个Dot/ICM效应器来干扰宿主泛素信号传递。 我们最近的研究表明，副作用家族的成员具有具有 操纵泛素信号的独特活动。首先，这些蛋白质含有脱泛素酶(DUB)。 有效地从泛素化蛋白质中去除泛素的模块。第二，这些蛋白质催化 通过一种不寻常的机制泛素化：该反应不需要E1、E2酶或ATP， 对所有描述的泛素化事件至关重要的因素。此外，这些新的泛素 操纵效应器是最大限度地实现细胞内细菌复制所必需的，这一点差别很大。 与大多数嗜肺乳杆菌Dot/ICM IV型效应器。作为一个额外的复杂性层，我们 发现副效应器的生物活性由SidJ效应器通过其逆转 通过一种似乎与经典配音明显不同的机制来副催化泛素化。通过 生化和结构分析，我们将研究这些蛋白质的作用机制。不同 在这些效应器中编码的功能域似乎协同工作，相互调节 对主机功能的平衡控制。我们将研究功能整合的生化基础 这些效应器中存在着不同的活动。这些研究不仅将揭示 细胞内病原体对宿主功能的利用，也将有可能修改目前的 了解泛素化，这是一种非常重要的信号机制。

Project summary Active modulation of host function is essential for the success of bacterial pathogens. The ubiquitin network regulates virtually every cellular process in eukaryotes, particularly those involved in the detection, recognition and response to infection. Accordingly, many pathogens target host ubiquitination for their benefits. Earlier studies revealed that Legionella pneumophila, the causative agent of Legionnaires' disease, interferes with host ubiquitin signaling by using at least 9 of its Dot/Icm effectors. Our recent study revealed that members of the SidE effector family feature enzymatic domains with unique activities for manipulating ubiquitin signals. First, these proteins contain a deubiquitinase (DUB) module that efficiently removes ubiquitin from ubiquitinated proteins. Second, these proteins catalyze ubiquitination by an unusual mechanism: the reaction does not require the E1, E2 enzymes or ATP, factors that are essential for all described ubiquitination events. Furthermore, these novel ubiquitin manipulating effectors are required for maximal intracellular bacterial replication, which differs sharply with the majority of L. pneumophila Dot/Icm type IV effectors. As an additional layer of complexity, we find that the biological activity of SidE effectors is regulated by the SidJ effector through its reversal of the SidE-catalyzed ubiquitination by a mechanism that appears to distinctly differ from classical DUBs. By biochemical and structural analyses, we will study the mechanism of action of these proteins. Different functional domains encoded in these effectors seem to work in concert to regulate each other for a balanced control of host functions. We will study biochemical basis of functional integration among distinct activities present within these effectors. These studies will not only reveal novel mechanisms of host function exploitation by intracellular pathogens, but also will have the potential to revise the current understanding of ubiquitination, an enormously important signaling mechanism.