Dataset Information

Insights into transcriptional silencing and anti-silencing in Shigella flexneri: a detailed molecular analysis of the icsP virulence locus.

ABSTRACT: Transcriptional silencing and anti-silencing mechanisms modulate bacterial physiology and virulence in many human pathogens. In Shigella species, many virulence plasmid genes are silenced by the histone-like nucleoid structuring protein H-NS and anti-silenced by the virulence gene regulator VirB. Despite the key role that these regulatory proteins play in Shigella virulence, their mechanisms of transcriptional control remain poorly understood. Here, we characterize the regulatory elements and their relative spacing requirements needed for the transcriptional silencing and anti-silencing of icsP, a locus that requires remotely located regulatory elements for both types of transcriptional control. Our findings highlight the flexibility of the regulatory elements' positions with respect to each other, and yet, a molecular roadblock docked between the VirB binding site and the upstream H-NS binding region abolishes transcriptional anti-silencing by VirB, providing insight into transcriptional anti-silencing. Our study also raises the need to re-evaluate the currently proposed VirB binding site. Models of transcriptional silencing and anti-silencing at this genetic locus are presented, and the implications for understanding these regulatory mechanisms in bacteria are discussed.

SUBMITTER: Weatherspoon-Griffin N

PROVIDER: S-EPMC6311345 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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Insights into transcriptional silencing and anti-silencing in Shigella flexneri: a detailed molecular analysis of the icsP virulence locus.

Weatherspoon-Griffin Natasha N Picker Michael A MA Pew Krystle L KL Park Hiromichi S HS Ginete Daren R DR Karney Monika Ma MM Usufzy Pashtana P Castellanos Maria I MI Duhart Juan Carlos JC Harrison Dustin J DJ Socea Jillian N JN Karabachev Alexander D AD Hensley Christopher T CT Howerton Amber J AJ Ojeda-Daulo Rosa R Immak Joy A JA Wing Helen J HJ

Molecular microbiology 20180323 5

Transcriptional silencing and anti-silencing mechanisms modulate bacterial physiology and virulence in many human pathogens. In Shigella species, many virulence plasmid genes are silenced by the histone-like nucleoid structuring protein H-NS and anti-silenced by the virulence gene regulator VirB. Despite the key role that these regulatory proteins play in Shigella virulence, their mechanisms of transcriptional control remain poorly understood. Here, we characterize the regulatory elements and th ...[more]

PMID: 29453862

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Project description:Shigella flexneri is an intracellular human pathogen that invades colonic cells and causes bloody diarrhea. S. flexneri evolved from commensal Escherichia coli, and genome comparisons reveal that S. flexneri has lost approximately 20% of its genes through the process of pathoadaptation, including a disproportionate number of genes associated with the turnover of the nucleotide-based second messenger cyclic di-GMP (c-di-GMP); however, the remaining c-di-GMP turnover enzymes are highly conserved. c-di-GMP regulates many behavioral changes in other bacteria in response to changing environmental conditions, including biofilm formation, but this signaling system has not been examined in S. flexneri. In this study, we expressed VCA0956, a constitutively active c-di-GMP synthesizing diguanylate cyclase (DGC) from Vibrio cholerae, in S. flexneri to determine if virulence phenotypes were regulated by c-di-GMP. We found that expressing VCA0956 in S. flexneri increased c-di-GMP levels, and this corresponds with increased biofilm formation and reduced acid resistance, host cell invasion, and plaque size. We examined the impact of VCA0956 expression on the S. flexneri transcriptome and found that genes related to acid resistance were repressed, and this corresponded with decreased survival to acid shock. We also found that individual S. flexneri DGC mutants exhibit reduced biofilm formation and reduced host cell invasion and plaque size, as well as increased resistance to acid shock. This study highlights the importance of c-di-GMP signaling in regulating S. flexneri virulence phenotypes. IMPORTANCE The intracellular human pathogen Shigella causes dysentery, resulting in as many as one million deaths per year. Currently, there is no approved vaccine for the prevention of shigellosis, and the incidence of antimicrobial resistance among Shigella species is on the rise. Here, we explored how the widely conserved c-di-GMP bacterial signaling system alters Shigella behaviors associated with pathogenesis. We found that expressing or removing enzymes associated with c-di-GMP synthesis results in changes in Shigella's ability to form biofilms, invade host cells, form lesions in host cell monolayers, and resist acid stress.

Dataset Information

Insights into transcriptional silencing and anti-silencing in Shigella flexneri: a detailed molecular analysis of the icsP virulence locus.

Publications

Insights into transcriptional silencing and anti-silencing in Shigella flexneri: a detailed molecular analysis of the icsP virulence locus.

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