Legionellapara-effectors target chromatin and promote bacterial replication

Abstract

Legionella pneumophilareplicates intracellularly by secreting effectors via a type IV secretion system. One of these effectors is a eukaryotic methyltransferase (RomA) that methylates K14 of histone H3 (H3K14me3) to counteract host immune responses. However, it is not known howL. pneumophilainfection catalyses H3K14 methylation as this residue is usually acetylated. Here we show thatL. pneumophilasecretes a eukaryotic-like histone deacetylase (LphD) that specifically targets H3K14ac and works in synergy with RomA. Both effectors target host chromatin and bind the HBO1 histone acetyltransferase complex that acetylates H3K14. Full activity of RomA is dependent on the presence of LphD as H3K14 methylation levels are significantly decreased in aΔlphDmutant. The dependency of these two chromatin-modifying effectors on each other is further substantiated by mutational and virulence assays revealing that the presence of only one of these two effectors impairs intracellular replication, while a double knockout (ΔlphDΔromA) can restore intracellular replication. Uniquely, we present evidence for "para-effectors", an effector pair, that actively and coordinately modify host histones to hijack the host response. The identification of epigenetic marks modulated by pathogens opens new vistas for the development of innovative therapeutic strategies to counteract bacterial infection and strengthening host defences.

A comprehensive two-hybrid analysis to explore theL. pneumophilaeffector-effector interactome

“…With over 300 effectors, L. pneumophila has the largest described bacterial effector arsenal (Ensminger, 2016) and several examples of effector interplay that finetune effector function and the progression of pathogenesis (Kubori et al , 2010; Müller et al , 2010; Neunuebel et al , 2011; Tan et al , 2011; Tan & Luo, 2011; Mukherjee et al , 2011; Jeong et al , 2015; Urbanus et al , 2016; Shames et al , 2017; Valleau et al , 2018; Gan et al , 2019a; Wan et al , 2019; Gan et al , 2020; Schator et al , 2023). We previously performed the first genetic interaction screen of bacterial effectors, where we expressed every possible combination of L. pneumophila str.…”

“…Effectors in the latter class have the potential to regulate an action on the host in a spatial and/or temporal manner (Kubori & Galán, 2003). Cooperative effector interplay has also been identified such as the Legionella pneumophila paraeffectors LphD and RomA which work consecutively by first deacetylating and then methylating K14 of host histone 3 (Schator et al , 2023). Other effectors, such as LegC2, LegC3, and LegC7, directly cooperate–forming a SNARE-like complex with the human hVAMP4 protein to modulate membrane fusion (Shi et al , 2016).…”

“…The intracellular pathogen L. pneumophila has the largest studied bacterial effector arsenal with over 300 effectors (Burstein et al , 2009; Huang et al , 2011; Zhu et al , 2011) and notably has several of such regulatory layers; indirect antagonist effectors (Müller et al , 2010; Neunuebel et al , 2011; Mukherjee et al , 2011; Tan & Luo, 2011; Tan et al , 2011; Valleau et al , 2018; Gan et al , 2019a; Wan et al , 2019; Gan et al , 2020; Song et al , 2021), cooperative paraeffectors (Schator et al , 2023) and several metaeffectors (Kubori et al , 2010; Jeong et al , 2015; Urbanus et al , 2016; Shames et al , 2017; Valleau et al , 2018; Bhogaraju et al , 2019; Black et al , 2019; Gan et al , 2019b; Joseph et al , 2020; Hsieh et al , 2021; McCloskey et al , 2021; Song et al , 2021), including the effector LubX for which the term metaeffector was coined (Kubori et al , 2010). L. pneumophila is the causative agent of Legionnaires’ disease (Fields et al , 2002) and uses the Dot/Icm Type IVB secretion system (T4SS) to deliver effectors to create a replicative niche in macrophages (Isberg et al , 2009) and protozoan species (Fields, 1996; Rowbotham, 1980; Molmeret et al , 2005; Faulkner et al , 2008; Watanabe et al , 2016; Boamah et al , 2017; Siddiqui et al , 2021).…”

Dual Control of Host Actin Polymerization by a Legionella Effector Pair

“…Recently, systematic screens [19,39] or individual studies of effector function [40][41][42][43][44][45][46][47][48] have identified some effectors that interfere with other effector activity rather than targeting a host cell protein. Regardless of the specific activities involved in these effector-effector interactions, two main models of interaction were revealed: indirect through counteracting modification of a shared host target, such as an effector pair recently described as para-effectors that target the host cell histone H3 [49], or direct through either complex formation or the modification of one effector by another. The direct interaction model led to the emerging concept of "metaeffector".…”

Dual control of host actin polymerization by aLegionellaeffector pair

“…Recently, systematic screens 19,40 or individual studies of effector function [41][42][43][44][45][46][47][48][49] have identified some effectors that interfere with other effector activity rather than targeting a host cell protein. Regardless the specific activities involved in these effector-effector interactions, two main models of interaction were revealed: indirect through counteracting modification of a shared host target, such as an effector pair recently described as para-effectors that target the host cell histone H3 50 ; or direct through either complex formation or the modification of one effector by another. The direct interaction model led to the emerging concept of « metaeffector ».…”