Regulation of <i>Helicobacter pylori</i> adherence by gene conversion

Talarico, Sarah; Whitefield, Shawn E.; Fero, Jutta; Haas, Rainer; Salama, Nina R.

doi:10.1111/j.1365-2958.2012.08073.x

Cited by 52 publications

(62 citation statements)

References 37 publications

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“…Hence, it can be proposed that high levels of recombination led to the splits in the Cronobacter genus, which later stabilized and became clonal in the more-recently evolved species like C. sakazakii and C. malonaticus. These latter two species are also the ones most associated with human clinical cases, suggesting a role of host adaptation in driving forward the evolution of the genus Cronobacter (41). Of course, one must keep in mind a possible bias in this analysis, since C. sakazakii is the most dominant species of the data set and therefore influences the numbers.…”

Section: Discussionmentioning

confidence: 99%

Diversity of the Cronobacter Genus as Revealed by Multilocus Sequence Typing

et al. 2012

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Cronobacter (previously known as Enterobacter sakazakii ) is a diverse bacterial genus consisting of seven species: C. sakazakii , C. malonaticus , C. turicensis , C. universalis , C. muytjensii , C. dublinensis , and C. condimenti . In this study, we have used a multilocus sequence typing (MLST) approach employing the alleles of 7 genes ( atpD , fusA , glnS , gltB , gyrB , infB , and ppsA ; total length, 3,036 bp) to investigate the phylogenetic relationship of 325 Cronobacter species isolates. Strains were chosen on the basis of their species, geographic and temporal distribution, source, and clinical outcome. The earliest strain was isolated from milk powder in 1950, and the earliest clinical strain was isolated in 1953. The existence of seven species was supported by MLST. Intraspecific variation ranged from low diversity in C. sakazakii to extensive diversity within some species, such as C. muytjensii and C. dublinensis , including evidence of gene conversion between species. The predominant species from clinical sources was found to be C. sakazakii. C. sakazakii sequence type 4 (ST4) was the predominant sequence type of cerebral spinal fluid isolates from cases of meningitis.

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Section: Discussionmentioning

confidence: 99%

Diversity of the Cronobacter Genus as Revealed by Multilocus Sequence Typing

et al. 2012

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“…Recent structural analysis has demonstrated that the basis for this functional diversity lies in two "diversity loops" within the carbohydrate binding site that represent areas of strong positive selection among babA sequences (13). Similarly, SabA shows polymorphism among clinical isolates in binding affinity to sialyl Lewis x (sLex) (31) and can be modulated by phase variation (32), gene conversion (33), and even variation in the length of a poly-T tract in the promoter region that serves as a rheostat-like mechanism to alter gene expression (34).…”

Section: Discussionmentioning

confidence: 99%

Dynamic Expression of the BabA Adhesin and Its BabB Paralog during Helicobacter pylori Infection in Rhesus Macaques

et al. 2017

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Most Helicobacter pylori strains express the BabA adhesin, which binds to ABO/Leb blood group antigens on gastric mucin and epithelial cells and is found more commonly in strains that cause peptic ulcers or gastric cancer, rather than asymptomatic infection. We and others have previously reported that in mice, gerbils, and rhesus macaques, expression of babA is lost, either by phase variation or by gene conversion, in which the babB paralog recombines into the babA locus. The functional significance of loss of babA expression is unknown. Here we report that in rhesus monkeys, there is independent selective pressure for loss of babA and for overexpression of BabB, which confers a fitness advantage. Surprisingly, loss of babA by phase variation or gene conversion is not dependent on the capacity of BabA protein to bind Leb, which suggests that it may have other, unrecognized functions. These findings have implications for the role of outer membrane protein diversity in persistent H. pylori infection.

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“…Additional layers of expression control are mediated by environmental signals acting through the two-component signal transduction system ArsRS (11). A recent study by Talarico et al (12) showed that recombination between the sabA locus and its paralogous locus, sabB, affects sabA expression significantly. Finally, recent evidence has shown that sabA and babA are coregulated with the host expression of mucins, to which H. pylori adheres in the gastric mu-cosal epithelium (14).…”

mentioning

confidence: 99%

“…Several studies have revealed the regulation of sabA expression in H. pylori to be very complex (11)(12)(13). Transcription of sabA is regulated via phase variation mediated by changes in dinucleotide repeats near the 5= end of the coding sequence (11).…”

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confidence: 99%

Repetitive Sequence Variations in the Promoter Region of the Adhesin-Encoding Gene sabA of Helicobacter pylori Affect Transcription

et al. 2014

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The pathogenesis of diseases elicited by the gastric pathogen Helicobacter pylori is partially determined by the effectiveness of adaptation to the variably acidic environment of the host stomach. Adaptation includes appropriate adherence to the gastric epithelium via outer membrane protein adhesins such as SabA. The expression of sabA is subject to regulation via phase variation in the promoter and coding regions as well as repression by the two-component system ArsRS. In this study, we investigated the role of a homopolymeric thymine [poly(T)] tract ؊50 to ؊33 relative to the sabA transcriptional start site in H. pylori strain J99. We quantified sabA expression in H. pylori J99 by quantitative reverse transcription-PCR (RT-PCR), demonstrating significant changes in sabA expression associated with experimental manipulations of poly(T) tract length. Mimicking the length increase of this tract by adding adenines instead of thymines had similar effects, while the addition of other nucleotides failed to affect sabA expression in the same manner. We hypothesize that modification of the poly(T) tract changes DNA topology, affecting regulatory protein interaction(s) or RNA polymerase binding efficiency. Additionally, we characterized the interaction between the sabA promoter region and ArsR, a response regulator affecting sabA expression. Using recombinant ArsR in electrophoretic mobility shift assays (EMSA), we localized binding to a sequence with partial dyad symmetry ؊20 and ؉38 relative to the sabA ؉1 site. The control of sabA expression by both ArsRS and phase variation at two distinct repeat regions suggests the control of sabA expression is both complex and vital to H. pylori infection.

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Regulation of Helicobacter pylori adherence by gene conversion

Cited by 52 publications

References 37 publications

Diversity of the Cronobacter Genus as Revealed by Multilocus Sequence Typing

Diversity of the Cronobacter Genus as Revealed by Multilocus Sequence Typing

Dynamic Expression of the BabA Adhesin and Its BabB Paralog during Helicobacter pylori Infection in Rhesus Macaques

Repetitive Sequence Variations in the Promoter Region of the Adhesin-Encoding Gene sabA of Helicobacter pylori Affect Transcription

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