Mechanism of atypical ubiquitination and deubiquitination by bacterial effectors

项目摘要 宿主功能的主动调节对于细菌病原体的成功是必不可少的。泛素 网络几乎调节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，许多病原体靶向宿主泛素化 为了他们的利益。早期的研究表明，嗜肺军团菌， 军团病通过使用至少9种其Dot/Icm效应物干扰宿主泛素信号传导。 我们最近的研究表明，SidE效应器家族的成员具有酶结构域， 操纵泛素信号的独特活性。首先，这些蛋白质含有去泛素化酶（DUB） 一种从泛素化蛋白中有效去除泛素的模块。其次，这些蛋白质催化 泛素化通过一种不寻常的机制：该反应不需要E1，E2酶或ATP， 这些因素对于所有描述的泛素化事件都是必不可少的。此外，这些新的泛素 操纵效应子是最大限度地细胞内细菌复制所必需的， 大多数L。pneumophila Dot/Icm IV型效应器。作为复杂性的一个附加层，我们 发现SidE效应子的生物学活性由SidJ效应子通过其逆转 SidE催化的泛素化的机制似乎明显不同于经典DUBs。通过 通过生物化学和结构分析，我们将研究这些蛋白质的作用机制。不同 这些效应子中编码的功能域似乎协同工作， 平衡控制主机功能。我们将研究功能整合的生化基础， 这些效应器中存在不同的活动。这些研究不仅将揭示新的机制， 宿主功能开发的细胞内病原体，而且也将有可能修改目前的 理解泛素化，一个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.