Data from: Diverse mechanisms of metaeffector activity in an intracellular bacterial pathogen, Legionella pneumophila.

Pathogens deliver complex arsenals of translocated effector proteins to host cells during infection, but the extent to which these proteins are regulated once inside the eukaryotic cell remains poorly defined. Amongst all bacterial pathogens, Legionella pneumophila maintains the largest known set of translocated substrates, delivering over 300 proteins to the host cell via its Type IVB, Icm/Dot translocation system. Backed by a few notable examples of effector-effector regulation in L. pneumophila, we sought to define the extent of this phenomenon through a systematic analysis of effector-effector functional interaction. We used Saccharomyces cerevisiae, an established proxy for the eukaryotic host, to query >108,000 pairwise genetic interactions between two compatible expression libraries of ~330 L. pneumophila translocated substrates. While capturing all known examples of effector-effector suppression, we identify fourteen novel translocated substrates that suppress the activity of other bacterial effectors and one pair with synergistic activities. In at least nine instances, this regulation is direct - a hallmark of an emerging class of proteins called metaeffectors, or "effectors of effectors." Through detailed structural and functional analysis, we show that metaeffector activity derives from a diverse range of mechanisms, shapes evolution, and can be used to reveal important aspects of each cognate effector's function. Metaeffectors, along with other, indirect, forms of effector-effector modulation, may be a common feature of many intracellular pathogens - with unrealized potential to inform our understanding of how pathogens regulate their interactions with the host cell.病原菌在侵染宿主细胞的过程中，会向宿主递送一套复杂的易位效应蛋白（translocated effector proteins）武器库，但这类蛋白进入真核细胞后的调控范围仍有待明确阐释。在所有细菌性病原菌中，嗜肺军团菌（Legionella pneumophila）拥有目前已知规模最大的易位效应底物库，可通过其IVB型Icm/Dot易位系统向宿主细胞递送超过300种蛋白。尽管目前仅有少数关于嗜肺军团菌效应蛋白间调控的经典研究案例，本研究旨在通过系统性分析效应蛋白间的功能互作，明确这类调控现象的覆盖范围。我们以酿酒酵母（Saccharomyces cerevisiae）——一种已被广泛验证的真核宿主模式生物——作为研究体系，对包含约330种嗜肺军团菌易位效应底物的两个兼容表达文库之间的超过108000对遗传互作进行了高通量筛选。本次研究不仅覆盖了所有已知的效应蛋白间抑制案例，还鉴定出14种全新的可抑制其他细菌效应蛋白活性的易位底物，以及1对具有协同活性的效应蛋白组合。其中至少9例调控为直接蛋白互作——这正是一类新兴蛋白——元效应蛋白（metaeffectors，即"效应因子的效应因子"）的标志性特征。通过深入的结构与功能分析，我们证实元效应蛋白的活性源自多样的作用机制，可塑造病原体的演化进程，同时还可用于解析对应效应蛋白的关键功能特征。元效应蛋白以及其他间接形式的效应蛋白间调控模式，可能是众多胞内病原菌的共性特征，其尚未被充分发掘的研究潜力，将有助于我们进一步理解病原菌如何调控其与宿主细胞的互作过程。