Long-Range Transcriptional Control of an Operon Necessary for Virulence-Critical ESX-1 Secretion in Mycobacterium tuberculosis

Hunt, Debbie M.; Sweeney, Nathan P.; Mori, Luisa; Whalan, Rachael H.; Comas, Iñaki; Norman, Laura; Cortes, Teresa; Arnvig, Kristine B.; Davis, E. A.; Stapleton, Melanie R.; Green, Jeffrey; Buxton, Roger S.

doi:10.1128/jb.00142-12

Cited by 38 publications

(43 citation statements)

References 56 publications

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“…In fact, ESX-1 was shown to regulate DNA conjugation of the nonpathogenic M. smegmatis (49,50). In contrast, the espACD operon is absent in M. smegmatis (43) and is perhaps indicative of its direct role in virulence mechanisms. In agreement with these results independent of its role as a secreted protein, EspA functions as a critical mediator of ESX-1-dependent virulence regulation (22).…”

Section: Discussionmentioning

confidence: 79%

“…It is possible that recruitment of PhoP changes DNA conformation (as it binds), which subsequently facilitates recruitment of EspR, a protein capable of participating in long range interactions (38,40). Thus, a DNA-dependent complex interplay of PhoP and EspR likely contributes to the precise regulation of the espACD operon, which perhaps is appropriate for an operon that plays such a critical role in the virulence mechanisms of M. tuberculosis (43). Clearly, as speculated in the schematic model (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…However, given the importance of the upstream control region of espACD operon, such a regulatory mechanism is unlikely to be applicable to other members of the M. tuberculosis complex. This is because the regulatory region of espACD for the closely related M. bovis includes 456 bp only (43), and for other members of the M. tuberculosis complex, the espACD promoter is even shorter arguing for a simpler transcription regulation without involving multiple regulators. Nevertheless, results reported in this work showing recruitment of a nucleoid-associated protein (as a functional partner) by a key regulator represents an additional layer of complexity that has perhaps evolved to further tune niche-specific gene expression.…”

Section: Discussionmentioning

confidence: 99%

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EspR-dependent ESAT-6 Protein Secretion of Mycobacterium tuberculosis Requires the Presence of Virulence Regulator PhoP

Kumar

Goyal

Bansal

et al. 2016

Journal of Biological Chemistry

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Attenuation of Mycobacterium bovis BCG strain is related to the loss of the RD1-encoded ESX-1 secretion system. The ESX-1 system secretes virulence factor ESAT-6 that plays a critical role in modulation of the host immune system, which is essential for establishment of a productive infection. Previous studies suggest that among the reasons for attenuation of Mycobacterium tuberculosis H37Ra is a mutation in the phoP gene that interferes with the ESX-1 secretion system and inhibits secretion of ESAT-6. Here, we identify a totally different and distinct regulatory mechanism involving PhoP and transcription regulator EspR on transcriptional control of the espACD operon, which is required for ESX-1-dependent ESAT-6 secretion. Although both of these regulators are capable of influencing espACD expression, we show that activation of espACD requires direct recruitment of both PhoP and EspR at the espACD promoter. The most fundamental insights are derived from the inhibition of EspR binding at the espACD regulatory region of the phoP mutant strain because of PhoP-EspR protein-protein interactions. Based on these results, a model is proposed suggesting how PhoP and EspR protein-protein interactions contribute to activation of espACD expression and, in turn, control ESAT-6 secretion, an essential pathogenic determinant of M. tuberculosis. Together, these results have significant implications on the mechanism of virulence regulation of M. tuberculosis.Mycobacterium tuberculosis uses the ESX-1 secretion system to transport virulence factors in host cells (1-5). ESX-1 secretion system is encoded by the genes of the esx-1 locus, which is highly conserved in members of the M. tuberculosis complex and in other pathogenic mycobacteria (5-9). The best known ESX-1 substrates, the secreted proteins EsxA (ESAT-6) and EsxB (CFP10), have been implicated in the majority of the ESX-1-dependent modulations of host cell defense (10 -19) and therefore are considered to be essential for virulence (12)(13)(14). Consistently, deletion of the esx-1 locus abrogates ESX-1-dependent secretion and strongly attenuates M. tuberculosis (15,20). Notably, the genes encoding esx-1, located within the M. tuberculosis RD1 locus, are absent in the attenuated Mycobacterium bovis BCG and the potential vaccine strain Mycobacterium microti (15,17). However, a chromosomally unlinked non-RD1 locus (Rv3616c-Rv3615c-Rv3614c, also designated as espA, espC, and espD) is essential for ESX-1 function (13, 21). In fact, EspA and EspC proteins themselves are substrates of the ESX-1 secretion system, thus constituting mutually dependent secretion of substrates, a notable feature of this secretion system. More recently, EspA of the tubercle bacilli has been implicated as a critical mediator of bacterial cell wall integrity and ESX-1-dependent virulence regulation (22).ESX-1 represents the first and the most characterized member of the ESX secretion family. Although intracellular concentrations of ESAT-6 are similar in both virulent M. tuberculosis H37Rv and the attenuated...

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Section: Discussionmentioning

confidence: 79%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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EspR-dependent ESAT-6 Protein Secretion of Mycobacterium tuberculosis Requires the Presence of Virulence Regulator PhoP

Kumar

Goyal

Bansal

et al. 2016

Journal of Biological Chemistry

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Section: Introductionmentioning

confidence: 99%

“…EspA is encoded within the espA operon, while esxA is located in RD-1 (Region of difference 1), which contains most ESX-1 genes (Mahairas et al, 1996). The intergenic region upstream of espA contains known or predicted binding sites for several different regulatory factors (Hunt et al, 2012;Pang et al, 2013;Rickman et al, 2005; Rosenberg et al, 2011), suggesting that ESX-1 activity could be modulated via altering espA expression.EspR, a key transcriptional regulator of ESX-1, directly regulates espA (Raghavan et al, 2008; Rosenberg et al, 2011). An espR mutant exhibited decreased transcription of the espA operon, loss of ESAT-6 secretion and reduced virulence (Raghavan et al, 2008).…”

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confidence: 99%

EspR, a regulator of the ESX-1 secretion system in Mycobacterium tuberculosis, is directly regulated by the two-component systems MprAB and PhoPR

et al. 2015

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EspR, a regulator of the ESX-1 secretion system in Mycobacterium tuberculosis, is directly regulated by the two-component systems MprAB and PhoPR INTRODUCTIONESX-1 (ESAT-6 secretion system-1) is a major virulence determinant of Mycobacterium tuberculosis, the causative agent of human tuberculosis. ESX-1 exports pathogenic and immunogenic proteins such as ESAT-6 (EsxA), EspA and other substrate proteins into host cells (Simeone et al., 2009). The secretion of EspA and ESAT-6 is mutually dependent, with deletion of espA resulting in loss of ESAT-6 secretion, and vice versa (Fortune et al., 2005). EspA is encoded within the espA operon, while esxA is located in RD-1 (Region of difference 1), which contains most ESX-1 genes (Mahairas et al., 1996). The intergenic region upstream of espA contains known or predicted binding sites for several different regulatory factors (Hunt et al., 2012;Pang et al., 2013;Rickman et al., 2005; Rosenberg et al., 2011), suggesting that ESX-1 activity could be modulated via altering espA expression.EspR, a key transcriptional regulator of ESX-1, directly regulates espA (Raghavan et al., 2008; Rosenberg et al., 2011). An espR mutant exhibited decreased transcription of the espA operon, loss of ESAT-6 secretion and reduced virulence (Raghavan et al., 2008). Higher-order oligomerization of EspR appears to be involved in cooperatively linking distant DNA sites, such as the three EspR binding sites in the espA promoter (Blasco et al., 2011; Rosenberg et al., 2011). Three EspR sites were also identified in the espR promoter (Blasco et al., 2012). However, these EspR sites are much closer than in the espA promoter, suggesting that EspR may have aAbbreviations: CRP, cAMP receptor protein; EMSA, electrophoresis mobility shift assay; ESX-1, ESAT-6 secretion system-1; L6, lineage 6; RD-1, Region of difference 1; TCS, two-component system.

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ChIP-Seq and the Complexity of Bacterial Transcriptional Regulation

Galagan

Lyubetskaya

Gomes

2012

Current Topics in Microbiology and Immunology

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Transcription factors (TFs) play a central role in regulating gene expression in all bacteria. Yet, until recently, studies of TF binding were limited to a small number of factors at a few genomic locations. Chromatin immunoprecipitation followed by sequencing enables mapping of binding sites for TFs in a global and high-throughput fashion. The NIAID funded TB systems biology project http://www.broadinstitute.org/annotation/tbsysbio/home.html aims to map the binding sites for every transcription factor in the genome of Mycobacterium tuberculosis (MTB), the causative agent of human TB. ChIP-Seq data already released through TBDB.org have provided new insight into the mechanisms of TB pathogenesis. But in addition, data from MTB are beginning to challenge many simplifying assumptions associated with gene regulation in all bacteria. In this chapter, we review the global aspects of TF binding in MTB and discuss the implications of these data for our understanding of bacterial gene regulation. We begin by reviewing the canonical model of bacterial transcriptional regulation using the lac operon as the standard paradigm. We then review the use of ChIP-Seq to map the binding sites of DNA-binding proteins and the application of this method to mapping TF binding sites in MTB. Finally, we discuss two aspects of the binding discovered by ChIP-Seq that were unexpected given the canonical model: the substantial binding outside the proximal promoter region and the large number of weak binding sites.

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Long-Range Transcriptional Control of an Operon Necessary for Virulence-Critical ESX-1 Secretion in Mycobacterium tuberculosis

Cited by 38 publications

References 56 publications

EspR-dependent ESAT-6 Protein Secretion of Mycobacterium tuberculosis Requires the Presence of Virulence Regulator PhoP

EspR-dependent ESAT-6 Protein Secretion of Mycobacterium tuberculosis Requires the Presence of Virulence Regulator PhoP

EspR, a regulator of the ESX-1 secretion system in Mycobacterium tuberculosis, is directly regulated by the two-component systems MprAB and PhoPR

ChIP-Seq and the Complexity of Bacterial Transcriptional Regulation

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