Project description:The principal virulence determinant of Mycobacterium tuberculosis (Mtb), the ESX-1 protein secretion system, is positively controlled at the transcriptional level by EspR. Depletion of EspR reportedly affects a small number of genes, both positively or negatively, including a key ESX-1 component, the espACD operon. EspR is also thought to be an ESX-1 substrate. Using EspR-specific antibodies in ChIP-Seq experiments (chromatin immunoprecipitation followed by ultra-high throughput DNA sequencing) we show that EspR binds to at least 165 loci on the Mtb genome. Included in the EspR regulon are genes encoding not only EspA, but also EspR itself, the ESX-2 and ESX-5 systems, a host of diverse cell wall functions, such as production of the complex lipid PDIM (phenolthiocerol dimycocerosate) and the PE/PPE cell-surface proteins. EspR binding sites are not restricted to promoter regions and can be clustered. This suggests that rather than functioning as a classical regulatory protein EspR acts globally as a nucleoid-associated protein capable of long-range interactions consistent with a recently established structural model. EspR expression was shown to be growth phase-dependent, peaking in the stationary phase. Overexpression in Mtb strain H37Rv revealed that EspR influences target gene expression both positively or negatively leading to growth arrest. At no stage was EspR secreted into the culture filtrate. Thus, rather than serving as a specific activator of a virulence locus, EspR is a novel nucleoid-associated protein, with both architectural and regulatory roles, that impacts cell wall functions and pathogenesis through multiple genes.
Project description:The principal virulence determinant of Mycobacterium tuberculosis (Mtb), the ESX-1 protein secretion system, is positively controlled at the transcriptional level by EspR. Depletion of EspR reportedly affects a small number of genes, both positively or negatively, including a key ESX-1 component, the espACD operon. EspR is also thought to be an ESX-1 substrate. Using EspR-specific antibodies in ChIP-Seq experiments (chromatin immunoprecipitation followed by ultra-high throughput DNA sequencing) we show that EspR binds to at least 165 loci on the Mtb genome. Included in the EspR regulon are genes encoding not only EspA, but also EspR itself, the ESX-2 and ESX-5 systems, a host of diverse cell wall functions, such as production of the complex lipid PDIM (phenolthiocerol dimycocerosate) and the PE/PPE cell-surface proteins. EspR binding sites are not restricted to promoter regions and can be clustered. This suggests that rather than functioning as a classical regulatory protein EspR acts globally as a nucleoid-associated protein capable of long-range interactions consistent with a recently established structural model. EspR expression was shown to be growth phase-dependent, peaking in the stationary phase. Overexpression in Mtb strain H37Rv revealed that EspR influences target gene expression both positively or negatively leading to growth arrest. At no stage was EspR secreted into the culture filtrate. Thus, rather than serving as a specific activator of a virulence locus, EspR is a novel nucleoid-associated protein, with both architectural and regulatory roles, that impacts cell wall functions and pathogenesis through multiple genes. ChIP-Seq of EspR in Mtb H37Rv at mid-log phase of growth. Two independent experiments were performed. Input DNA (No IP) was used as a control.
Project description:A handful of nucleoid-associated proteins (NAPs) regulate the vast majority of genes in a bacterial cell. H-NS, the Histone-like Nucleoid-Structuring protein, is one of these NAPs and protects Escherichia coli from foreign gene expression. Though lacking any sequence similarity with E. coli H-NS, Rv3852 was annotated as the H-NS ortholog in Mycobacterium tuberculosis, as it resembles human histone H1. The role of H-NS was thoroughly investigated by immunoblotting, subcellular localization, construction of an unmarked hns deletion in the M. tuberculosis genome and subsequent analysis of the resulting Δhns strain. We found that H-NS was predominantly present in the logarithmic growth phase with a decrease in protein abundance in stationary phase. Furthermore, it was strongly associated with the cell membrane and not detected in the cytosolic fraction, nor was it secreted. The Δhns strain displayed no growth defect or morphological abnormalities. Quantitative measurement of nucleoid localization in Δhns compared to the parental H37Rv strain showed no difference in nucleoid position or spread. Infection of macrophages as well as severe combined immunodeficient (SCID) mice demonstrated that loss of H-NS had no detectable influence on the virulence of M. tuberculosis. Only few genes wre differentially expressed in the Δhns strain. We thus conclude that M. tuberculosis H-NS is not involved in pathogenesis and is not a typical NAP.
Project description:Bacterial nucleoid-associated proteins play important roles in chromosome organization and global gene regulation. We find that Lsr2 of Mycobacterium tuberculosis is a novel nucleoid-associated protein that specifically binds AT-rich regions of the genome, including regions encoding major virulence factors, such as the ESX secretion systems, the lipid virulence factors PDIM/PGL, and the PE/PPE families of antigenic proteins. Comparison of genome-wide binding data with expression data indicates that Lsr2 binding results in transcriptional repression. Domain swamping experiments demonstrate that Lsr2 has an N-terminal dimerization domain and a C-terminal DNA binding domain. NMR analysis of the DNA binding domain of Lsr2 and its interaction with DNA reveals a novel structure and a unique mechanism that enables Lsr2 to discriminately target AT-rich sequences through interactions with the minor groove of DNA. Taken together, we provide evidence that mycobacteria have employed a structurally distinct molecule with an apparently different DNA recognition mechanism to achieve an equivalent function as the Enterobacteriaceae H-NS, coordinating global gene regulation and virulence in this group of medically important bacteria. Comparison of Lsr2 chromatin-immunoprecipitated DNA sequences to total reference DNA
Project description:Bacterial nucleoid-associated proteins play important roles in chromosome organization and global gene regulation. We find that Lsr2 of Mycobacterium tuberculosis is a novel nucleoid-associated protein that specifically binds AT-rich regions of the genome, including regions encoding major virulence factors, such as the ESX secretion systems, the lipid virulence factors PDIM/PGL, and the PE/PPE families of antigenic proteins. Comparison of genome-wide binding data with expression data indicates that Lsr2 binding results in transcriptional repression. Domain swamping experiments demonstrate that Lsr2 has an N-terminal dimerization domain and a C-terminal DNA binding domain. NMR analysis of the DNA binding domain of Lsr2 and its interaction with DNA reveals a novel structure and a unique mechanism that enables Lsr2 to discriminately target AT-rich sequences through interactions with the minor groove of DNA. Taken together, we provide evidence that mycobacteria have employed a structurally distinct molecule with an apparently different DNA recognition mechanism to achieve an equivalent function as the Enterobacteriaceae H-NS, coordinating global gene regulation and virulence in this group of medically important bacteria.
Project description:Mycobacterium tuberculosis, a pathogen of global importance, utilizes the ESX-1 protein secretion system to export virulence factors that disarm host macrophages. Although this secretory pathway is critical for virulence, how ESX-1 is regulated is completely unknown. Here we show that EspR (Rv3849) is a key regulator of ESX-1. EspR activates transcription of an operon that includes three ESX-1 components, Rv3616c-Rv3614c, whose expression in turn promotes secretion of ESX-1 substrates. Keywords: Strain comparison Comparison of the global gene expression of three M.tb strains grown in log phase: Erdman strain of M.tb, espR transposon mutant, and the espR transposon mutant complemented with the espR gene
Project description:Mycobacterium tuberculosis, a pathogen of global importance, utilizes the ESX-1 protein secretion system to export virulence factors that disarm host macrophages. Although this secretory pathway is critical for virulence, how ESX-1 is regulated is completely unknown. Here we show that EspR (Rv3849) is a key regulator of ESX-1. EspR activates transcription of an operon that includes three ESX-1 components, Rv3616c-Rv3614c, whose expression in turn promotes secretion of ESX-1 substrates. Keywords: Strain comparison
Project description:Mycobacterium tuberculosis, a pathogen of global importance, utilizes the ESX-1 protein secretion system to export virulence factors that disarm host macrophages. Although this secretory pathway is critical for virulence, how ESX-1 is regulated is completely unknown. Here we show that EspR (Rv3849) is a key regulator of ESX-1. EspR activates transcription of an operon that includes three ESX-1 components, Rv3616c-Rv3614c, whose expression in turn promotes secretion of ESX-1 substrates. Keywords: Strain comparison
Project description:Mycobacterium tuberculosis, a pathogen of global importance, utilizes the ESX-1 protein secretion system to export virulence factors that disarm host macrophages. Although this secretory pathway is critical for virulence, how ESX-1 is regulated is completely unknown. Here we show that EspR (Rv3849) is a key regulator of ESX-1. EspR activates transcription of an operon that includes three ESX-1 components, Rv3616c-Rv3614c, whose expression in turn promotes secretion of ESX-1 substrates. Keywords: Strain comparison
Project description:Mycobacterium tuberculosis, a pathogen of global importance, utilizes the ESX-1 protein secretion system to export virulence factors that disarm host macrophages. Although this secretory pathway is critical for virulence, how ESX-1 is regulated is completely unknown. Here we show that EspR (Rv3849) is a key regulator of ESX-1. EspR activates transcription of an operon that includes three ESX-1 components, Rv3616c-Rv3614c, whose expression in turn promotes secretion of ESX-1 substrates. Keywords: Strain comparison