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Yeong-Jae Seok

Publications and source records attributed to Yeong-Jae Seok.

9 recordsLinked to original sources
PubMed2026

Sex-Dependent Microbial and Host Profiles Following Fecal Microbiota and Bifidobacterium longum Treatment in Stress-Induced Gut Dysbiosis.

BACKGROUND/AIMS: Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder influenced by stress, microbial dysbiosis, and immune activation. Microbiota-directed therapies, including fecal microbiota transplantation and probiotics, show promise, but their sex-specific effects remain unclear. We compared the therapeutic effects of lyophilized fecal microbiota (LFM) with Bifidobacterium longum BBH016 in male and female Wistar rats subjected to repeated water avoidance stress. METHODS: Fecal pellet output (FPO), colonic mast cell infiltration, and fecal short-chain fatty acids were measured. Gut microbial composition and function were analyzed by 16S rRNA sequencing and Kyoto Encyclopedia of Genes and Genomes pathway prediction. RESULTS: Both interventions significantly reduced FPO and mast cell infiltration in males but had less pronounced effects in females. Microbiota analyses revealed sex-dependent responses, with distinct microbial trajectories in each treatment group. Using linear discriminant analysis effect size, we identified seven key taxa with treatment- or sex-specific enrichment. Alistipes onderdonkii and Bacteroides uniformis consistently increased in both LFM- and B. longum-treated groups, regardless of sex. Bacteroides finegoldii and Barnesiella intestinihominis were specifically enriched in the LFM group. In males, Blautia faecis and Fusicatenibacter saccharivorans were enriched following the interventions, whereas Parabacteroides goldsteinii appeared exclusively in stressed males. Functional predictions revealed the enrichment of estrogen signaling and bile acid pathways in males and the attenuation of proinflammatory pathways in females following LFM. Correlations between microbial taxa and host outcomes were predominantly observed in male rats. CONCLUSIONS: These findings highlight sex-specific microbial and host responses to microbiota-targeted therapies in a stress-induced IBS model, emphasizing sex as a biological variable in designing personalized microbiome-based treatments.

Animals↗
PubMed2006

Transcriptional regulatory cascade for elastase production in Vibrio vulnificus: LuxO activates luxT expression and LuxT represses smcR expression.

Vibrio vulnificus causes diseases through actions of various virulence factors, including the elastase encoded by the vvpE gene. Through transposon mutagenesis of V. vulnificus, vvpE expression was shown to be increased by luxO mutation. Since the vvpE gene is known to be positively regulated by SmcR via direct binding to the vvpE promoter, the role of LuxO in smcR expression was investigated. The luxAB-transcriptional fusions containing different lengths of the smcR promoter region indicated that the smcR transcription was negatively regulated by LuxO and that a specific upstream region of the smcR gene was required for this repression. Since LuxO is a known member of positive regulators, the negative regulation of smcR transcription by LuxO prompted us to identify the factor(s) linking LuxO and smcR transcription. LuxT was isolated in a ligand fishing experiment using the smcR upstream region as bait, and smcR expression was increased by luxT mutation. Recombinant LuxT bound to a specific upstream region of the smcR gene, -154 to -129 relative to the smcR transcription start site. The expression of luxT was positively regulated by LuxO, and the luxT promoter region contained a putative LuxO-binding site. Mutagenesis of the LuxO-binding site in the luxT promoter region resulted in a loss of transcriptional control by LuxO. Therefore, this study demonstrates a transcriptional regulatory cascade for elastase production, where LuxO activates luxT transcription and LuxT represses smcR transcription.

Bacterial Proteins↗
PubMed2006

In vitro reconstitution of catabolite repression in Escherichia coli.

A widely accepted model for catabolite repression posits that phospho-IIAGlc of the bacterial phosphotransferase system activates adenylyl cyclase (AC) activity. For many years, attempts to observe such regulatory properties of AC in vitro have been unsuccessful. To further study the regulation, AC was produced fused to the transmembrane segments of the serine chemoreceptor Tsr. Cells harboring Tsr-AC and normal AC, expressed from the cya promoter on a low copy number vector, exhibit similar behavior with respect to elevation of cAMP levels resulting from deletion of crp, expressing the catabolite regulatory protein. Membrane-bound Tsr-AC exhibits activity comparable with the native form of AC. Tsr-AC binds IIAGlc specifically, regardless of its phosphorylation state, but not the two general phosphotransferase system proteins, enzyme I and HPr; IIAGlc binding is localized to the C-terminal region of AC. Binding to membranes of either dephospho- or phospho-IIAGlc has no effect on AC activity. However, in the presence of an Escherichia coli extract, P-IIAGlc, but not IIAGlc, stimulates AC activity. Based on these findings of a direct interaction of IIAGlc with AC, but activity regulation only in the presence of E. coli extract, a revised model for AC activity regulation is proposed.

Adenylyl Cyclase Inhibitors↗
PubMed2005

Glucose repression of the Escherichia coli sdhCDAB operon, revisited: regulation by the CRP*cAMP complex.

Expression of the Escherichia coli sdhCDAB operon encoding the succinate dehydrogenase complex is regulated in response to growth conditions, such as anaerobiosis and carbon sources. An anaerobic repression of sdhCDAB is known to be mediated by the ArcB/A two-component system and the global Fnr anaerobic regulator. While the cAMP receptor protein (CRP) and Cra (formerly FruR) are known as key mediators of catabolite repression, they have been excluded from the glucose repression of the sdhCDAB operon. Although the glucose repression of sdhCDAB was reported to involve a mechanism dependent on the ptsG expression, the molecular mechanism underlying the glucose repression has never been clarified. In this study, we re-examined the mechanism of the sdhCDAB repression by glucose and found that CRP directly regulates expression of the sdhCDAB operon and that the glucose repression of this operon occurs in a cAMP-dependent manner. The levels of phosphorylated enzyme IIA(Glc) and intracellular cAMP on various carbon sources were proportional to the expression levels of sdhC-lacZ. Disruption of crp or cya completely abolished the glucose repression of sdhC-lacZ expression. Together with data showing correlation between the intracellular cAMP concentrations and the sdhC-lacZ expression levels in several mutants and wild type, in vitro transcription assays suggest that the decrease in the CRP.cAMP level in the presence of glucose is the major determinant of the glucose repression of the sdhCDAB operon.

Bacterial Proteins↗
PubMed2005

DNA looping-mediated repression by histone-like protein H-NS: specific requirement of Esigma70 as a cofactor for looping.

Transcription initiation by RNA polymerase (RNP) carrying the house-keeping sigma subunit, sigma70 (Esigma70), is repressed by H-NS at a number of promoters including hdeABp in Escherichia coli, while initiation with RNP carrying the stationary phase sigma, sigma38 (Esigma38), is not. We investigated the molecular mechanism of selective repression by H-NS to identify the differences in transcription initiation by the two forms of RNPs, which show indistinguishable promoter selectivities in vitro. Using hdeABp as a model promoter, we observed with purified components that H-NS, acting at a sequence centered at -118, selectively repressed transcription by Esigma70. This selective repression is attributed to the differences in the interactions between hdeABp and the two forms of RNPs, since no other factor is required for the repression. We observed that the two forms of RNPs could form an open initiation complex (RP(O)) at hdeABp, but that Esigma70 failed to initiate transcription in the presence of H-NS. Interestingly, KMnO4 assays and high-resolution atomic force microscopy (AFM) revealed that hdeABp DNA wrapped around Esigma70 more tightly than around Esigma38, resulting in the potential crossing over of the DNA arms that project out of Esigma70 . RP(O) but not out of Esigma38 . RP(O). Based on these observations, we postulated that H-NS bound at -118 laterally extends by the cooperative recruitment of H-NS molecules to the promoter-downstream sequence joined by wrapping of the DNA around Esigma70 . RP(O), resulting in effective sealing of the DNA loop and trapping of Esigma70. Such a ternary complex of H-NS . Esigma70 hdeABp was demonstrated by AFM. In this case, therefore, Esigma70 acts as a cofactor for DNA looping. Expression of this class of genes by Esigma38 in the stationary phase is not due to its promoter specificity but to the architecture of the promoter . Esigma38 complex.

Bacterial Proteins↗
PubMed2005

Requirement of the dephospho-form of enzyme IIANtr for derepression of Escherichia coli K-12 ilvBN expression.

While the proteins of the phosphoenolpyruvate:carbohydrate phosphotransferase system (carbohydrate PTS) have been shown to regulate numerous targets, little such information is available for the nitrogen-metabolic phosphotransferase system (nitrogen-metabolic PTS). To elucidate the physiological role of the nitrogen-metabolic PTS, we carried out phenotype microarray (PM) analysis with Escherichia coli K-12 strain MG1655 deleted for the ptsP gene encoding the first enzyme of the nitrogen-metabolic PTS. Together with the PM data, growth studies revealed that a ptsN (encoding enzyme IIA(Ntr)) mutant became extremely sensitive to leucine-containing peptides (LCPs), while both ptsP (encoding enzyme I(Ntr)) and ptsO (encoding NPr) mutants were more resistant than wild type. The toxicity of LCPs was found to be due to leucine and the dephospho-form of enzyme IIA(Ntr) was found to be necessary to neutralize leucine toxicity. Further studies showed that the dephospho-form of enzyme IIA(Ntr) is required for derepression of the ilvBN operon encoding acetohydroxy acid synthase I catalysing the first step common to the biosynthesis of the branched-chain amino acids.

Acetolactate Synthase↗
PubMed2004

Expression of ptsG encoding the major glucose transporter is regulated by ArcA in Escherichia coli.

Because the phosphoenolpyruvate:sugar phosphotransferase system plays multiple regulatory roles in addition to the phosphorylation-coupled transport of many sugars in bacteria, synthesis of its protein components is regulated in a highly sophisticated way. Thus far, the cAMP receptor protein (CRP) complex and Mlc are known to be the major regulators of ptsHIcrr and ptsG expression in response to the availability of carbon sources. In this report, we performed ligand fishing experiments by using the promoters of ptsHIcrr and ptsG as bait to find out new factors involved in the transcriptional regulation of the phosphoenolpyruvate:sugar phosphotransferase system in Escherichia coli, and we found that the anaerobic regulator ArcA specifically binds to the promoters. Deletion of the arcA gene caused about a 2-fold increase in the ptsG expression, and overexpression of ArcA significantly decreased glucose consumption. In vitro transcription assays showed that phospho-ArcA (ArcA-P) represses ptsG P1 transcription. DNase I footprinting experiments revealed that ArcA-P binds to three sites upstream of the ptsG P1 promoter, two of which overlap the CRP-binding sites, and the ArcA-P binding decreases the CRP binding that is essential for the ptsG P1 transcription. These results suggest that the response regulator ArcA regulates expression of enzyme IICB(Glc) mediating the first step of glucose metabolism in response to the redox conditions of growth in E. coli.

Bacterial Outer Membrane Proteins↗
PubMed2004

A novel fermentation/respiration switch protein regulated by enzyme IIAGlc in Escherichia coli.

The bacterial phosphoenolpyruvate:sugar phosphotransferase system regulates a variety of physiological processes as well as effecting sugar transport. The crr gene product (enzyme IIA(Glc) (IIA(Glc))) mediates some of these regulatory phenomena. In this report, we characterize a novel IIA(Glc)-binding protein from Escherichia coli extracts, discovered using ligand-fishing with surface plasmon resonance spectroscopy. This protein, which we named FrsA (fermentation/respiration switch protein), is the 47-kDa product of the yafA gene, previously denoted as "function unknown." FrsA forms a 1:1 complex specifically with the unphosphorylated form of IIA(Glc), with the highest affinity of any protein thus far shown to interact with IIA(Glc). Orthologs of FrsA have been found to exist only in facultative anaerobes belonging to the gamma-proteobacterial group. Disruption of frsA increased cellular respiration on several sugars including glucose, while increased FrsA expression resulted in an increased fermentation rate on these sugars with the concomitant accumulation of mixed-acid fermentation products. These results suggest that IIA(Glc) regulates the flux between respiration and fermentation pathways by sensing the available sugar species via a phosphorylation state-dependent interaction with FrsA.

Amino Acid Sequence↗