Hha has a defined regulatory role that is not dependent upon H-NS or StpA

Solórzano, Carla; Srikumar, Shabarinath; Canals, Rocı́o; Juárez, Antonio; Paytubi, Sònia; Madrid, Cristina

doi:10.3389/fmicb.2015.00773

Cited by 13 publications

(12 citation statements)

References 84 publications

(140 reference statements)

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“…Although it lacks a separate DNA-binding domain (DBD) present in H-NS and StpA, Hha regulates many genes in association with H-NS (Figure 1A and B ; Refs. 17 , 20 , 21 ), and may affect others independently of H-NS ( 22 ).…”

Section: Introductionmentioning

confidence: 99%

StpA and Hha stimulate pausing by RNA polymerase by promoting DNA–DNA bridging of H-NS filaments

Boudreau

Hron

Qin

et al. 2018

Nucleic Acids Research

106

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In enterobacteria, AT-rich horizontally acquired genes, including virulence genes, are silenced through the actions of at least three nucleoid-associated proteins (NAPs): H-NS, StpA and Hha. These proteins form gene-silencing nucleoprotein filaments through direct DNA binding by H-NS and StpA homodimers or heterodimers. Both linear and bridged filaments, in which NAPs bind one or two DNA segments, respectively, have been observed. Hha can interact with H-NS or StpA filaments, but itself lacks a DNA-binding domain. Filaments composed of H-NS alone can inhibit transcription initiation and, in the bridged conformation, slow elongating RNA polymerase (RNAP) by promoting backtracking at pause sites. How the other NAPs modulate these effects of H-NS is unknown, despite evidence that they help regulate subsets of silenced genes in vivo (e.g. in pathogenicity islands). Here we report that Hha and StpA greatly enhance H-NS-stimulated pausing by RNAP at 20°C. StpA:H-NS or StpA-only filaments also stimulate pausing at 37°C, a temperature at which Hha:H-NS or H-NS-only filaments have much less effect. In addition, we report that both Hha and StpA greatly stimulate DNA–DNA bridging by H-NS filaments. Together, these observations indicate that Hha and StpA can affect H-NS-mediated gene regulation by stimulating bridging of H-NS/DNA filaments.

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Section: Introductionmentioning

confidence: 99%

StpA and Hha stimulate pausing by RNA polymerase by promoting DNA–DNA bridging of H-NS filaments

Boudreau

Hron

Qin

et al. 2018

Nucleic Acids Research

106

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“…Recently, Hha-YdgT have been shown to favor H-NS DNA-bridging activity, thanks to conformational changes of H-NS from a close to an open state [54]. On the contrary, few reports show that Hha binds to specific regulatory sequences independently of H-NS, although Hha has no DNA binding domain [38,39,55]. A few other papers report a Hha direct regulation but careful interpretation should be done since, in these studies, Hha protein purification was performed in wild-type E. coli and thus a co-purification of Hha with H-NS and/or StpA could have occurred [56,57].…”

Section: Discussionmentioning

confidence: 99%

“…Consequently, we cannot completely rule out the hypothesis that Hha-YdgT act indirectly through another unknown regulatory protein. A recent work identified 120 genes regulated by Hha independently of H-NS/StpA [39] among which two fimbrial genes belonging to sth and stj operons, but not the pef operon. However, bacteria were grown in neutral medium in this study and consequently not in conditions optimal for Pef expression.…”

Section: Discussionmentioning

confidence: 99%

“…In this model, H-NS in its oligomerized form binds to the target DNA and interacts with Hha that increases H-NS DNA-binding thanks to positively charged residues on its surface and thus improves H-NS silencing. However, a repression of the transcription of 120 genes by Hha independently of H-NS/StpA has been observed by Solórzano et al and a direct interaction of Hha with the rtsA promoter region has been described [38,39].…”

Section: Introductionmentioning

confidence: 96%

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H-NS is the major repressor of Salmonella Typhimurium Pef fimbriae expression

et al. 2019

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Fimbriae play an important role in adhesion and are therefore essential for the interaction of bacteria with the environments they encounter. Most of them are expressed in vivo but not in vitro, thus making difficult the full characterization of these fimbriae. Here, we characterized the silencing of plasmid-encoded fimbriae (Pef) expression, encoded by the pef operon, in the worldwide pathogen Salmonella Typhimurium. We demonstrated that the nucleoid-associated proteins H-NS and Hha, and their respective paralogs StpA and YdgT, negatively regulate at pH 5.1 and pH 7.1 the transcription of the pef operon. Two promoters, PpefB and PpefA, direct the transcription of this operon. All the nucleoid-associated proteins silence the PpefB promoter and H-NS also targets the PpefA promoter. While Hha and YdgT are mainly considered as acting primarily through H-NS to modulate gene transcription, our results strongly suggest that Hha and YdgT silence pef transcription at acidic pH either by interacting with StpA or independently of H-NS and StpA. We also confirmed the previously described post-transcriptional repression of Pef fimbriae by CsrA titration via the fim mRNA and CsrB and CsrC sRNA. Finally, among all these regulators, H-NS clearly appeared as the major repressor of Pef expression. These results open new avenues of research to better characterize the regulation of these bacterial adhesive proteins and to clarify their role in the virulence of pathogens.

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“…In the case of plasmid R1 and R100, it has been conclusively shown that transcription initiated at the P Y promoter proceeds well beyond the finO gene and includes the rmoA (hha) gene (141). Hha is a H-NS-like nucleoid-associated protein (NAP) that can modulate gene expression in enterobacteria (142) together with or independently of H-NS (143). Like Hha, another protein, TraR, which is a RNAP modulator is encoded on the tra operon and is therefore coregulated with DNA transfer genes.…”

Section: Regulation Of Dna Transfer Genes: On and Off Switchesmentioning

confidence: 99%

Spread and Persistence of Virulence and Antibiotic Resistance Genes: A Ride on the F Plasmid Conjugation Module

Koraimann

2018

EcoSal Plus

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The F plasmid or F-factor is a large, 100-kbp, circular conjugative plasmid of and was originally described as a vector for horizontal gene transfer and gene recombination in the late 1940s. Since then, F and related F-like plasmids have served as role models for bacterial conjugation. At present, more than 200 different F-like plasmids with highly related DNA transfer genes, including those for the assembly of a type IV secretion apparatus, are completely sequenced. They belong to the phylogenetically related MOBA group. F-like plasmids are present in enterobacterial hosts isolated from clinical as well as environmental samples all over the world. As conjugative plasmids, F-like plasmids carry genetic modules enabling plasmid replication, stable maintenance, and DNA transfer. In this plasmid backbone of approximately 60 kbp, the DNA transfer genes occupy the largest and mostly conserved part. Subgroups of MOBA plasmids can be defined based on the similarity of TraJ, a protein required for DNA transfer gene expression. In addition, F-like plasmids harbor accessory cargo genes, frequently embedded within transposons and/or integrons, which harness their host bacteria with antibiotic resistance and virulence genes, causing increasingly severe problems for the treatment of infectious diseases. Here, I focus on key genetic elements and their encoded proteins present on the F-factor and other typical F-like plasmids belonging to the MOBA group of conjugative plasmids.

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Hha has a defined regulatory role that is not dependent upon H-NS or StpA

Cited by 13 publications

References 84 publications

StpA and Hha stimulate pausing by RNA polymerase by promoting DNA–DNA bridging of H-NS filaments

StpA and Hha stimulate pausing by RNA polymerase by promoting DNA–DNA bridging of H-NS filaments

H-NS is the major repressor of Salmonella Typhimurium Pef fimbriae expression

Spread and Persistence of Virulence and Antibiotic Resistance Genes: A Ride on the F Plasmid Conjugation Module

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