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The Subtleties and Contrasts of the LeuO Regulator in Salmonella Typhi: Implications in the Immune Response.

Guadarrama C, Villaseñor T, Calva E - Front Immunol (2014)

Bottom Line: SPI-1 encodes transcriptional factors that participate in the expression of virulence factors encoded in the island.However, there are transcriptional factors encoded outside the island that also participate in the expression of SPI-1-encoded genes.Hence, the understanding of the LeuO regulon implies a role of bacterial genetic regulation in determining the host immune response.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México , Cuernavaca , Mexico.

ABSTRACT
Salmonella are facultative intracellular pathogens. Salmonella infection occurs mainly by expression of two Salmonella pathogenicity Islands (SPI-1 and SPI-2). SPI-1 encodes transcriptional factors that participate in the expression of virulence factors encoded in the island. However, there are transcriptional factors encoded outside the island that also participate in the expression of SPI-1-encoded genes. Upon infection, bacteria are capable of avoiding the host immune response with several strategies that involve several virulence factors under the control of transcriptional regulators. Interestingly, LeuO a transcriptional global regulator which is encoded outside of any SPI, is proposed to be part of a complex regulatory network that involves expression of several genes that help bacteria to survive stress conditions and, also, induces the expression of porins that have been shown to be immunogens and can thus be considered as antigenic candidates for acellular vaccines. Hence, the understanding of the LeuO regulon implies a role of bacterial genetic regulation in determining the host immune response.

No MeSH data available.


Related in: MedlinePlus

Schematic representation of the LeuO regulon in Escherichia coli, S. enterica serovars Typhimurium and Typhi, and Yersinia enterocolitica. LeuO is a dual regulator that can induce the expression of several genes (arrows) and also is capable of repressing gene expression (lines). When acting as a repressor it has been suggested to function as a backup for H-NS; nevertheless in several cases LeuO acts as a derepressor of gene expression by displacement or prevention of H-NS repression. Recently, LeuO has been denominated as a global antagonist of H-NS in E. coli and in S. enterica serovar Typhimurium. The expression of leuO is repressed by H-NS, although there are some stress conditions when LeuO can be detected in E. coli. Also, in Salmonella it has been described as an interesting case of differential control of transcriptional regulation, which depends on LeuO concentration. Parentheses depict the proteins coded by the indicated genes. Small arrows denote the several functions for the LeuO-regulated genes.
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Figure 1: Schematic representation of the LeuO regulon in Escherichia coli, S. enterica serovars Typhimurium and Typhi, and Yersinia enterocolitica. LeuO is a dual regulator that can induce the expression of several genes (arrows) and also is capable of repressing gene expression (lines). When acting as a repressor it has been suggested to function as a backup for H-NS; nevertheless in several cases LeuO acts as a derepressor of gene expression by displacement or prevention of H-NS repression. Recently, LeuO has been denominated as a global antagonist of H-NS in E. coli and in S. enterica serovar Typhimurium. The expression of leuO is repressed by H-NS, although there are some stress conditions when LeuO can be detected in E. coli. Also, in Salmonella it has been described as an interesting case of differential control of transcriptional regulation, which depends on LeuO concentration. Parentheses depict the proteins coded by the indicated genes. Small arrows denote the several functions for the LeuO-regulated genes.

Mentions: LeuO is part of the LysR-type transcriptional regulators (LTTRs), the largest family of transcriptional regulators in prokaryotes. In consequence, they regulate a wide variety of genes that are involved in a diversity of cellular functions such as biosynthesis of amino acids, catabolism of aromatic compounds, antibiotic resistance, oxidative stress response, nitrogen fixation, quorum sensing and virulence (Figure 1) (37–40). Many structural studies have shown an organization of an N-terminal DNA-binding domain (DBD) with a winged Helix-Turn-Helix (wHTH) motif; and a long linker helix (LH) involved in dimerization that connects the DBD with the C-terminal effector binding domain (EBD) or regulatory domain (RD) (37, 41–43). These regulators are proteins between 300 and 350 residues, mostly acting as transcriptional activators that bind to A–T rich DNA sequences in similar positions.


The Subtleties and Contrasts of the LeuO Regulator in Salmonella Typhi: Implications in the Immune Response.

Guadarrama C, Villaseñor T, Calva E - Front Immunol (2014)

Schematic representation of the LeuO regulon in Escherichia coli, S. enterica serovars Typhimurium and Typhi, and Yersinia enterocolitica. LeuO is a dual regulator that can induce the expression of several genes (arrows) and also is capable of repressing gene expression (lines). When acting as a repressor it has been suggested to function as a backup for H-NS; nevertheless in several cases LeuO acts as a derepressor of gene expression by displacement or prevention of H-NS repression. Recently, LeuO has been denominated as a global antagonist of H-NS in E. coli and in S. enterica serovar Typhimurium. The expression of leuO is repressed by H-NS, although there are some stress conditions when LeuO can be detected in E. coli. Also, in Salmonella it has been described as an interesting case of differential control of transcriptional regulation, which depends on LeuO concentration. Parentheses depict the proteins coded by the indicated genes. Small arrows denote the several functions for the LeuO-regulated genes.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4264507&req=5

Figure 1: Schematic representation of the LeuO regulon in Escherichia coli, S. enterica serovars Typhimurium and Typhi, and Yersinia enterocolitica. LeuO is a dual regulator that can induce the expression of several genes (arrows) and also is capable of repressing gene expression (lines). When acting as a repressor it has been suggested to function as a backup for H-NS; nevertheless in several cases LeuO acts as a derepressor of gene expression by displacement or prevention of H-NS repression. Recently, LeuO has been denominated as a global antagonist of H-NS in E. coli and in S. enterica serovar Typhimurium. The expression of leuO is repressed by H-NS, although there are some stress conditions when LeuO can be detected in E. coli. Also, in Salmonella it has been described as an interesting case of differential control of transcriptional regulation, which depends on LeuO concentration. Parentheses depict the proteins coded by the indicated genes. Small arrows denote the several functions for the LeuO-regulated genes.
Mentions: LeuO is part of the LysR-type transcriptional regulators (LTTRs), the largest family of transcriptional regulators in prokaryotes. In consequence, they regulate a wide variety of genes that are involved in a diversity of cellular functions such as biosynthesis of amino acids, catabolism of aromatic compounds, antibiotic resistance, oxidative stress response, nitrogen fixation, quorum sensing and virulence (Figure 1) (37–40). Many structural studies have shown an organization of an N-terminal DNA-binding domain (DBD) with a winged Helix-Turn-Helix (wHTH) motif; and a long linker helix (LH) involved in dimerization that connects the DBD with the C-terminal effector binding domain (EBD) or regulatory domain (RD) (37, 41–43). These regulators are proteins between 300 and 350 residues, mostly acting as transcriptional activators that bind to A–T rich DNA sequences in similar positions.

Bottom Line: SPI-1 encodes transcriptional factors that participate in the expression of virulence factors encoded in the island.However, there are transcriptional factors encoded outside the island that also participate in the expression of SPI-1-encoded genes.Hence, the understanding of the LeuO regulon implies a role of bacterial genetic regulation in determining the host immune response.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México , Cuernavaca , Mexico.

ABSTRACT
Salmonella are facultative intracellular pathogens. Salmonella infection occurs mainly by expression of two Salmonella pathogenicity Islands (SPI-1 and SPI-2). SPI-1 encodes transcriptional factors that participate in the expression of virulence factors encoded in the island. However, there are transcriptional factors encoded outside the island that also participate in the expression of SPI-1-encoded genes. Upon infection, bacteria are capable of avoiding the host immune response with several strategies that involve several virulence factors under the control of transcriptional regulators. Interestingly, LeuO a transcriptional global regulator which is encoded outside of any SPI, is proposed to be part of a complex regulatory network that involves expression of several genes that help bacteria to survive stress conditions and, also, induces the expression of porins that have been shown to be immunogens and can thus be considered as antigenic candidates for acellular vaccines. Hence, the understanding of the LeuO regulon implies a role of bacterial genetic regulation in determining the host immune response.

No MeSH data available.


Related in: MedlinePlus