scholarly journals Control of Methionine Synthesis and Uptake by MetR and Homocysteine in Streptococcus mutans

2007 ◽  
Vol 189 (19) ◽  
pp. 7032-7044 ◽  
Author(s):  
Brice Sperandio ◽  
Céline Gautier ◽  
Stephen McGovern ◽  
Dusko S. Ehrlich ◽  
Pierre Renault ◽  
...  
Keyword(s):  
Streptococcus Mutans ◽  
Transcriptional Activation ◽  
Gene Clusters ◽  
Common Mechanism ◽  
Methionine Biosynthesis ◽  
Promoter Regions ◽  
Streptococcal Species ◽  
Dna Complex

ABSTRACT MetR (formerly Smu.1225), a regulator of the LysR family, controls key genes for methionine supply in Streptococcus mutans. An S. mutans metR mutant is unable to transport l-methionine and to grow in the absence of this amino acid. Accordingly, MetR activates transcription by binding to the promoter regions of two gene clusters and smu.1487, whose products are involved in methionine biosynthesis (MetEF and Smu.1487) and uptake (AtmBDE). Transcriptional activation by MetR requires the presence of a 17-bp palindromic sequence, the Met box. Base substitutions in the Met box hinder the formation of a MetR-DNA complex and abolish MetR-dependent activation, showing that Met boxes correspond to MetR recognition sites. Activation by MetR occurs in methionine-depleted medium and is rapidly triggered under nonactivating conditions by the addition of homocysteine. This intermediate of methionine biosynthesis increases the affinity of MetR for DNA in vitro and appears to be the MetR coeffector in vivo. Homocysteine plays a crucial role in methionine metabolic gene regulation by controlling MetR activity. A similar mechanism of homocysteine- and MetR-dependent control of methionine biosynthetic genes operates in S. thermophilus. These data suggest a common mechanism for the regulation of the methionine supply in streptococci. However, some streptococcal species are unable to synthesize the homocysteine coeffector. This intriguing feature is discussed in the light of comparative genomics and streptococcal ecology.

scholarly journals Binding and transcriptional activation of non-flagellar genes by the Escherichia coli flagellar master regulator FlhD2C2

Microbiology ◽  
2005 ◽  
Vol 151 (6) ◽  
pp. 1779-1788 ◽  
Author(s):  
Graham P. Stafford ◽  
Tomoo Ogi ◽  
Colin Hughes
Keyword(s):  
Escherichia Coli ◽  
Dna Sequences ◽  
Transcriptional Activation ◽  
Binding Sites ◽  
Class Ii ◽  
Promoter Regions ◽  
E Coli ◽  
Flagellar Genes

The gene hierarchy directing biogenesis of peritrichous flagella on the surface of Escherichia coli and other enterobacteria is controlled by the heterotetrameric master transcriptional regulator FlhD2C2. To assess the extent to which FlhD2C2 directly activates promoters of a wider regulon, a computational screen of the E. coli genome was used to search for gene-proximal DNA sequences similar to the 42–44 bp inverted repeat FlhD2C2 binding consensus. This identified the binding sequences upstream of all eight flagella class II operons, and also putative novel FlhD2C2 binding sites in the promoter regions of 39 non-flagellar genes. Nine representative non-flagellar promoter regions were all bound in vitro by active reconstituted FlhD2C2 over the K D range 38–356 nM, and of the nine corresponding chromosomal promoter–lacZ fusions, those of the four genes b1904, b2446, wzz fepE and gltI showed up to 50-fold dependence on FlhD2C2 in vivo. In comparison, four representative flagella class II promoters bound FlhD2C2 in the K D range 12–43 nM and were upregulated in vivo 30- to 990-fold. The FlhD2C2-binding sites of the four regulated non-flagellar genes overlap by 1 or 2 bp the predicted −35 motif of the FlhD2C2-activated σ 70 promoters, as is the case with FlhD2C2-dependent class II flagellar promoters. The data indicate a wider FlhD2C2 regulon, in which non-flagellar genes are bound and activated directly, albeit less strongly, by the same mechanism as that regulating the flagella gene hierarchy.

scholarly journals Murine Salivary Amylase Protects Against Streptococcus mutans-Induced Caries

2021 ◽  
Vol 12 ◽  
Author(s):  
David J. Culp ◽  
Bently Robinson ◽  
Melanie N. Cash
Keyword(s):  
Streptococcus Mutans ◽  
Dental Enamel ◽  
Major Constituent ◽  
Oral Microbiota ◽  
Salivary Amylase ◽  
Plaque Ph ◽  
Streptococcal Species ◽  
The Impact

Saliva protects dental surfaces against cavities (i. e., dental caries), a highly prevalent infectious disease frequently associated with acidogenic Streptococcus mutans. Substantial in vitro evidence supports amylase, a major constituent of saliva, as either protective against caries or supporting caries. We therefore produced mice with targeted deletion of salivary amylase (Amy1) and determined the impact on caries in mice challenged with S. mutans and fed a diet rich in sucrose to promote caries. Total smooth surface and sulcal caries were 2.35-fold and 1.79-fold greater in knockout mice, respectively, plus caries severities were twofold or greater on sulcal and smooth surfaces. In in vitro experiments with samples of whole stimulated saliva, amylase expression did not affect the adherence of S. mutans to saliva-coated hydroxyapatite and slightly increased its aggregation in solution (i.e., oral clearance). Conversely, S. mutans in biofilms formed in saliva with 1% glucose displayed no differences when cultured on polystyrene, but on hydroxyapatite was 40% less with amylase expression, suggesting that recognition by S. mutans of amylase bound to hydroxyapatite suppresses growth. However, this effect was overshadowed in vivo, as the recoveries of S. mutans from dental plaque were similar between both groups of mice, suggesting that amylase expression helps decrease plaque acids from S. mutans that dissolve dental enamel. With amylase deletion, commensal streptococcal species increased from ~75 to 90% of the total oral microbiota, suggesting that amylase may promote higher plaque pH by supporting colonization by base-producing oral commensals. Importantly, collective results indicate that amylase may serve as a biomarker of caries risk.

Subnuclear compartmentalization of sequence-specific transcription factors and regulation of eukaryotic gene expression

2005 ◽  
Vol 83 (4) ◽  
pp. 535-547 ◽  
Author(s):  
Gareth N Corry ◽  
D Alan Underhill
Keyword(s):  
Gene Expression ◽  
Transcription Factor ◽  
Transcription Factors ◽  
Transcriptional Activation ◽  
Current Knowledge ◽  
Nuclear Architecture ◽  
Subnuclear Localization ◽  
Modular Structures

To date, the majority of the research regarding eukaryotic transcription factors has focused on characterizing their function primarily through in vitro methods. These studies have revealed that transcription factors are essentially modular structures, containing separate regions that participate in such activities as DNA binding, protein–protein interaction, and transcriptional activation or repression. To fully comprehend the behavior of a given transcription factor, however, these domains must be analyzed in the context of the entire protein, and in certain cases the context of a multiprotein complex. Furthermore, it must be appreciated that transcription factors function in the nucleus, where they must contend with a variety of factors, including the nuclear architecture, chromatin domains, chromosome territories, and cell-cycle-associated processes. Recent examinations of transcription factors in the nucleus have clarified the behavior of these proteins in vivo and have increased our understanding of how gene expression is regulated in eukaryotes. Here, we review the current knowledge regarding sequence-specific transcription factor compartmentalization within the nucleus and discuss its impact on the regulation of such processes as activation or repression of gene expression and interaction with coregulatory factors.Key words: transcription, subnuclear localization, chromatin, gene expression, nuclear architecture.

scholarly journals Activation of MAT2A-RIP1 signaling axis reprograms monocytes in gastric cancer

2021 ◽  
Vol 9 (2) ◽  
pp. e001364
Author(s):  
Yan Zhang ◽  
Hui Yang ◽  
Jun Zhao ◽  
Ping Wan ◽  
Ye Hu ◽  
...  
Keyword(s):  
Gastric Cancer ◽  
Cell Metabolism ◽  
Vital Role ◽  
Methionine Metabolism ◽  
Promoter Regions ◽  
Normal Tissues ◽  
Methionine Cycle

BackgroundThe activation of tumor-associated macrophages (TAMs) facilitates the progression of gastric cancer (GC). Cell metabolism reprogramming has been shown to play a vital role in the polarization of TAMs. However, the role of methionine metabolism in function of TAMs remains to be explored.MethodsMonocytes/macrophages were isolated from peripheral blood, tumor tissues or normal tissues from healthy donors or patients with GC. The role of methionine metabolism in the activation of TAMs was evaluated with both in vivo analyses and in vitro experiments. Pharmacological inhibition of the methionine cycle and modulation of key metabolic genes was employed, where molecular and biological analyses were performed.ResultsTAMs have increased methionine cycle activity that are mainly attributed to elevated methionine adenosyltransferase II alpha (MAT2A) levels. MAT2A modulates the activation and maintenance of the phenotype of TAMs and mediates the upregulation of RIP1 by increasing the histone H3K4 methylation (H3K4me3) at its promoter regions.ConclusionsOur data cast light on a novel mechanism by which methionine metabolism regulates the anti-inflammatory functions of monocytes in GC. MAT2A might be a potential therapeutic target for cancer cells as well as TAMs in GC.

scholarly journals Prrx1 promotes stemness and angiogenesis via activating TGF-β/smad pathway and upregulating proangiogenic factors in glioma

2021 ◽  
Vol 12 (6) ◽  
Author(s):  
Zetao Chen ◽  
Yihong Chen ◽  
Yan Li ◽  
Weidong Lian ◽  
Kehong Zheng ◽  
...  
Keyword(s):  
Stem Cells ◽  
Therapeutic Strategy ◽  
Critical Role ◽  
Glioma Stem Cells ◽  
Promoter Regions ◽  
Aberrant Expression ◽  
Smad Pathway ◽  
Tgf Β1

AbstractGlioma is one of the most lethal cancers with highly vascularized networks and growing evidences have identified glioma stem cells (GSCs) to account for excessive angiogenesis in glioma. Aberrant expression of paired-related homeobox1 (Prrx1) has been functionally associated with cancer stem cells including GSCs. In this study, Prrx1 was found to be markedly upregulated in glioma specimens and elevated Prrx1 expression was inversely correlated with prognosis of glioma patients. Prrx1 potentiated stemness acquisition in non-stem tumor cells (NSTCs) and stemness maintenance in GSCs, accompanied with increased expression of stemness markers such as SOX2. Prrx1 also promoted glioma angiogenesis by upregulating proangiogenic factors such as VEGF. Consistently, silencing Prrx1 markedly inhibited glioma proliferation, stemness, and angiogenesis in vivo. Using a combination of subcellular proteomics and in vitro analyses, we revealed that Prrx1 directly bound to the promoter regions of TGF-β1 gene, upregulated TGF-β1 expression, and ultimately activated the TGF-β/smad pathway. Silencing TGF-β1 mitigated the malignant behaviors induced by Prrx1. Activation of this pathway cooperates with Prrx1 to upregulate the expression of stemness-related genes and proangiogenic factors. In summary, our findings revealed that Prrx1/TGF-β/smad signal axis exerted a critical role in glioma stemness and angiogeneis. Disrupting the function of this signal axis might represent a new therapeutic strategy in glioma patients.

scholarly journals CDK13 upregulation-induced formation of the positive feedback loop among circCDK13, miR-212-5p/miR-449a and E2F5 contributes to prostate carcinogenesis

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Jin-Chun Qi ◽  
Zhan Yang ◽  
Tao Lin ◽  
Long Ma ◽  
Ya-Xuan Wang ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Transcriptional Activation ◽  
Positive Feedback ◽  
Feedback Loop ◽  
Biological Effects ◽  
Therapeutic Benefit ◽  
Loss Of Function ◽  
Positive Feedback Loop

Abstract Background Both E2F transcription factor and cyclin-dependent kinases (CDKs), which increase or decrease E2F activity by phosphorylating E2F or its partner, are involved in the control of cell proliferation, and some circRNAs and miRNAs regulate the expression of E2F and CDKs. However, little is known about whether dysregulation among E2Fs, CDKs, circRNAs and miRNAs occurs in human PCa. Methods The expression levels of CDK13 in PCa tissues and different cell lines were determined by quantitative real-time PCR and Western blot analysis. In vitro and in vivo assays were preformed to explore the biological effects of CDK13 in PCa cells. Co-immunoprecipitation anlysis coupled with mass spectrometry was used to identify E2F5 interaction with CDK13. A CRISPR-Cas9 complex was used to activate endogenous CDK13 and circCDK13 expression. Furthermore, the mechanism of circCDK13 was investigated by using loss-of-function and gain-of-function assays in vitro and in vivo. Results Here we show that CDK13 is significantly upregulated in human PCa tissues. CDK13 depletion and overexpression in PCa cells decrease and increase, respectively, cell proliferation, and the pro-proliferation effect of CDK13 is strengthened by its interaction with E2F5. Mechanistically, transcriptional activation of endogenous CDK13, but not the forced expression of CDK13 by its expression vector, remarkably promotes E2F5 protein expression by facilitating circCDK13 formation. Further, the upregulation of E2F5 enhances CDK13 transcription and promotes circCDK13 biogenesis, which in turn sponges miR-212-5p/449a and thus relieves their repression of the E2F5 expression, subsequently leading to the upregulation of E2F5 expression and PCa cell proliferation. Conclusions These findings suggest that CDK13 upregulation-induced formation of the positive feedback loop among circCDK13, miR-212-5p/miR-449a and E2F5 is responsible for PCa development. Targeting this newly identified regulatory axis may provide therapeutic benefit against PCa progression and drug resistance.

scholarly journals NR5A2 transcriptional activation by BRD4 promotes pancreatic cancer progression by upregulating GDF15

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Feng Guo ◽  
Yingke Zhou ◽  
Hui Guo ◽  
Dianyun Ren ◽  
Xin Jin ◽  
...  
Keyword(s):  
Pancreatic Cancer ◽  
Cancer Cells ◽  
Cancer Progression ◽  
Transcriptional Activation ◽  
Ductal Adenocarcinoma ◽  
Pancreatic Cancer Cells ◽  
Gene Sets ◽  
And Migration

AbstractNR5A2 is a transcription factor regulating the expression of various oncogenes. However, the role of NR5A2 and the specific regulatory mechanism of NR5A2 in pancreatic ductal adenocarcinoma (PDAC) are not thoroughly studied. In our study, Western blotting, real-time PCR, and immunohistochemistry were conducted to assess the expression levels of different molecules. Wound-healing, MTS, colony formation, and transwell assays were employed to evaluate the malignant potential of pancreatic cancer cells. We demonstrated that NR5A2 acted as a negative prognostic biomarker in PDAC. NR5A2 silencing inhibited the proliferation and migration abilities of pancreatic cancer cells in vitro and in vivo. While NR5A2 overexpression markedly promoted both events in vitro. We further identified that NR5A2 was transcriptionally upregulated by BRD4 in pancreatic cancer cells and this was confirmed by Chromatin immunoprecipitation (ChIP) and ChIP-qPCR. Besides, transcriptome RNA sequencing (RNA-Seq) was performed to explore the cancer-promoting effects of NR5A2, we found that GDF15 is a component of multiple down-regulated tumor-promoting gene sets after NR5A2 was silenced. Next, we showed that NR5A2 enhanced the malignancy of pancreatic cancer cells by inducing the transcription of GDF15. Collectively, our findings suggest that NR5A2 expression is induced by BRD4. In turn, NR5A2 activates the transcription of GDF15, promoting pancreatic cancer progression. Therefore, NR5A2 and GDF15 could be promising therapeutic targets in pancreatic cancer.

scholarly journals Expression of laminin γ 1 cultured hepatocytes involves repeated CTC and GC elements in the LAMC1 promoter

1996 ◽  
Vol 313 (3) ◽  
pp. 745-752 ◽  
Author(s):  
Françoise LEVAVASSEUR ◽  
Jocelyne LIÉTARD ◽  
Kohei OGAWA ◽  
Nathalie THÉRET ◽  
Peter D. BURBELO ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Hepatoma Cell ◽  
Primary Cultures ◽  
Regulatory Elements ◽  
Hepatoma Cells ◽  
Basement Membranes ◽  
Major Protein ◽  
Cultured Hepatocytes

Laminin γ1 chain is present in all basement membranes and is expressed at high levels in various diseases, such as hepatic fibrosis. We have identified cis- and trans-acting elements involved in the regulation of this gene in normal rat liver, as well as in hepatocyte primary cultures and hepatoma cell lines. Northern-blot analyses showed that laminin γ1 mRNA was barely detectable in freshly isolated hepatocytes and expressed at high levels in hepatocyte primary cultures, as early as 4 h after liver dissociation. Actinomycin D and cycloheximide treatment in vivo and in vitro indicated that laminin γ1 overexpression in cultured hepatocytes was under the control of transcriptional mechanisms. Transfection of deletion mutants of the 5´ flanking region of murine LAMC1 gene in hepatoma cells that constitutively express laminin γ1 indicated that regulatory elements were located between -594 bp and -94 bp. This segment included GC- and CTC-containing motifs. Gel-shift analyses showed that two complexes were resolved with different affinity for the CTC sequence depending on the location of the GC box. The pattern of complex formation with nuclear factors from freshly isolated and cultured hepatocytes was different from that obtained with total liver and similar to that with hepatoma cells. Southwestern analysis indicated that several polypeptides bound the CTC-rich sequence. Affinity chromatography demonstrated that a Mr 60000 polypeptide was a major protein binding to the CTC motif. This polypeptide is probably involved in the transcriptional activation of various proto-oncogenes and extracellular matrix genes that are expressed at high levels in both hepatoma cells and early hepatocyte cultures.

scholarly journals Arsenic Directly Binds to and Activates the Yeast AP-1-Like Transcription Factor Yap8

2015 ◽  
Vol 36 (6) ◽  
pp. 913-922 ◽  
Author(s):  
Nallani Vijay Kumar ◽  
Jianbo Yang ◽  
Jitesh K. Pillai ◽  
Swati Rawat ◽  
Carlos Solano ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Transcriptional Activation ◽  
Transcriptional Response ◽  
Transcriptional Regulator ◽  
Yeast Protein ◽  
Content Type ◽  
Arsenic Tolerance ◽  
Arsenic Sensing

The AP-1-like transcription factor Yap8 is critical for arsenic tolerance in the yeastSaccharomyces cerevisiae. However, the mechanism by which Yap8 senses the presence of arsenic and activates transcription of detoxification genes is unknown. Here we demonstrate that Yap8 directly binds to trivalent arsenite [As(III)]in vitroandin vivoand that approximately one As(III) molecule is bound per molecule of Yap8. As(III) is coordinated by three sulfur atoms in purified Yap8, and our genetic and biochemical data identify the cysteine residues that form the binding site as Cys132, Cys137, and Cys274. As(III) binding by Yap8 does not require an additional yeast protein, and Yap8 is regulated neither at the level of localization nor at the level of DNA binding. Instead, our data are consistent with a model in which a DNA-bound form of Yap8 acts directly as an As(III) sensor. Binding of As(III) to Yap8 triggers a conformational change that in turn brings about a transcriptional response. Thus, As(III) binding to Yap8 acts as a molecular switch that converts inactive Yap8 into an active transcriptional regulator. This is the first report to demonstrate how a eukaryotic protein couples arsenic sensing to transcriptional activation.

scholarly journals Apoptosis in metanephric development.

1992 ◽  
Vol 119 (5) ◽  
pp. 1327-1333 ◽  
Author(s):  
C Koseki ◽  
D Herzlinger ◽  
Q al-Awqati
Keyword(s):  
Spinal Cord ◽  
Protein Kinase ◽  
Transcriptional Activation ◽  
Phorbol Esters ◽  
Dna Degradation ◽  
Morphological Evidence ◽  
Metanephric Mesenchyme ◽  
Embryonic Spinal Cord

During metanephric development, non-polarized mesenchymal cells are induced to form the epithelial structures of the nephron following interaction with extracellular matrix proteins and factors produced by the inducing tissue, ureteric bud. This induction can occur in a transfilter organ culture system where it can also be produced by heterologous cells such as the embryonic spinal cord. We found that when embryonic mesenchyme was induced in vitro and in vivo, many of the cells surrounding the new epithelium showed morphological evidence of programmed cell death (apoptosis) such as condensed nuclei, fragmented cytoplasm, and cell shrinking. A biochemical correlate of apoptosis is the transcriptional activation of a calcium-sensitive endonuclease. Indeed, DNA isolated from uninduced mesenchyme showed progressive degradation, a process that was prevented by treatment with actinomycin-D or cycloheximide and by buffering intracellular calcium. These results demonstrate that the metanephric mesenchyme is programmed for apoptosis. Incubation of mesenchyme with a heterologous inducer, embryonic spinal cord prevented this DNA degradation. To investigate the mechanism by which inducers prevented apoptosis we tested the effects of protein kinase C modulators on this process. Phorbol esters mimicked the effects of the inducer and staurosporine, an inhibitor of this protein kinase, prevented the effect of the inducer. EGF also prevented DNA degradation but did not lead to differentiation. These results demonstrate that conversion of mesenchyme to epithelial requires at least two steps, rescue of the mesenchyme from apoptosis and induction of differentiation.

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