scholarly journals The Drosophila Ortholog of MLL3 and MLL4 , trithorax related , Functions as a Negative Regulator of Tissue Growth

2013 ◽  
Vol 33 (9) ◽  
pp. 1702-1710 ◽  
Author(s):  
Hiroshi Kanda ◽  
Alexander Nguyen ◽  
Leslie Chen ◽  
Hideyuki Okano ◽  
Iswar K. Hariharan
Keyword(s):  
Histone H3 ◽  
Tissue Growth ◽  
Negative Regulator ◽  
Cyclin B ◽  
Wild Type ◽  
H3k4 Methylation ◽  
Content Type ◽  
Promote Cell Survival ◽  
Low Levels ◽  
Mutant Cells

The human MLL genes ( MLL1 to MLL4 ) and their Drosophila orthologs, trithorax ( trx ) and trithorax related ( trr ), encode proteins capable of methylating histone H3 on lysine 4. MLL1 and MLL2 are most similar to trx , while MLL3 and MLL4 are more closely related to trr . Several MLL genes are mutated in human cancers, but how these proteins regulate cell proliferation is not known. Here we show that trr mutant cells have a growth advantage over their wild-type neighbors and display changes in the levels of multiple proteins that regulate growth and cell division, including Notch, Capicua, and cyclin B. trr mutant clones display markedly reduced levels of H3K4 monomethylation without obvious changes in the levels of H3K4 di- and trimethylation. The trr mutant phenotype resembles that of Utx , which encodes a H3K27 demethylase, consistent with the observation that Trr and Utx are found in the same protein complex. In contrast to the overgrowth displayed by trr mutant tissue, trx clones are underrepresented, express low levels of the antiapoptotic protein Diap1, and exhibit only modest changes in global levels of H3K4 methylation. Thus, in Drosophila eye imaginal discs, Trr, likely functioning together with Utx, restricts tissue growth. In contrast, Trx appears to promote cell survival.

scholarly journals Regulation of Exocyst Function in Pollen Tube Growth by Phosphorylation of Exocyst Subunit EXO70C2

2021 ◽  
Vol 11 ◽  
Author(s):  
Antonietta Saccomanno ◽  
Martin Potocký ◽  
Přemysl Pejchar ◽  
Michal Hála ◽  
Hiromasa Shikata ◽  
...  
Keyword(s):  
Pollen Tube ◽  
Pollen Tube Growth ◽  
Negative Regulator ◽  
Tube Growth ◽  
Wild Type ◽  
Functional Studies ◽  
Tobacco Pollen ◽  
Pollen Tube Growth Rate ◽  
Mutant Cells ◽  
Dose Dependent

Exocyst is a heterooctameric protein complex crucial for the tethering of secretory vesicles to the plasma membrane during exocytosis. Compared to other eukaryotes, exocyst subunit EXO70 is represented by many isoforms in land plants whose cell biological and biological roles, as well as modes of regulation remain largely unknown. Here, we present data on the phospho-regulation of exocyst isoform EXO70C2, which we previously identified as a putative negative regulator of exocyst function in pollen tube growth. A comprehensive phosphoproteomic analysis revealed phosphorylation of EXO70C2 at multiple sites. We have now performed localization and functional studies of phospho-dead and phospho-mimetic variants of Arabidopsis EXO70C2 in transiently transformed tobacco pollen tubes and stably transformed Arabidopsis wild type and exo70C2 mutant plants. Our data reveal a dose-dependent effect of AtEXO70C2 overexpression on pollen tube growth rate and cellular architecture. We show that changes of the AtEXO70C2 phosphorylation status lead to distinct outcomes in wild type and exo70c2 mutant cells, suggesting a complex regulatory pattern. On the other side, phosphorylation does not affect the cytoplasmic localization of AtEXO70C2 or its interaction with putative secretion inhibitor ROH1 in the yeast two-hybrid system.

scholarly journals Cytoplasmic accumulation of cdc25B phosphatase in mitosis triggers centrosomal microtubule nucleation in HeLa cells

1996 ◽  
Vol 109 (5) ◽  
pp. 1081-1093 ◽  
Author(s):  
B.G. Gabrielli ◽  
C.P. De Souza ◽  
I.D. Tonks ◽  
J.M. Clark ◽  
N.K. Hayward ◽  
...  
Keyword(s):  
Functional Status ◽  
Hela Cells ◽  
Mitotic Spindle ◽  
Dominant Negative ◽  
Cyclin B ◽  
Wild Type ◽  
Microtubule Nucleation ◽  
Cytoplasmic Accumulation ◽  
Low Levels ◽  
Essential Prerequisite

The formation of the mitotic spindle is an essential prerequisite for successful mitosis. The dramatic changes in the level of microtubule (Mt) nucleation at the centrosomes and Mt dynamics that occur in prophase are presumed to be initiated through the activity of cdc2/cyclin B. Here we present data that the cdc25B isoform functions to activate the cytoplasmic pool of cdc2/cyclin B responsible for these events. In contrast to cdc25C, cdc25B is present at low levels in HeLa cells during interphase, but sharply increases in prophase, when cdc25B accumulation in the cytoplasm correlates with prophase spindle formation. Overexpression of wild type and dominant negative mutants of cdc25B and cdc25C shows that prophase Mt nucleation is a consequence of cytoplasmic cdc25B activity, and that cdc25C regulates nuclear G2/M events. Our data also suggest that the functional status of the centrosome can regulate nuclear mitotic events.

scholarly journals Loss of RNA Chaperone Hfq Unveils a Toxic Pathway in Pseudomonas aeruginosa

2019 ◽  
Vol 201 (20) ◽  
Author(s):  
Ian T. Hill ◽  
Thomas Tallo ◽  
Matthew J. Dorman ◽  
Simon L. Dove
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Opportunistic Pathogen ◽  
Toxic Effects ◽  
Growth Defect ◽  
Wild Type ◽  
Rna Chaperone ◽  
Small Protein ◽  
Content Type ◽  
Transcription Regulator ◽  
Mutant Cells

ABSTRACT Hfq is an RNA chaperone that serves as a master regulator of bacterial physiology. Here we show that in the opportunistic pathogen Pseudomonas aeruginosa, the loss of Hfq can result in a dramatic reduction in growth in a manner that is dependent upon MexT, a transcription regulator that governs antibiotic resistance in this organism. Using a combination of chromatin immunoprecipitation with high-throughput sequencing and transposon insertion sequencing, we identify the MexT-activated genes responsible for mediating the growth defect of hfq mutant cells. These include a newly identified MexT-controlled gene that we call hilR. We demonstrate that hilR encodes a small protein that is acutely toxic to wild-type cells when produced ectopically. Furthermore, we show that hilR expression is negatively regulated by Hfq, offering a possible explanation for the growth defect of hfq mutant cells. Finally, we present evidence that the expression of MexT-activated genes is dependent upon GshA, an enzyme involved in the synthesis of glutathione. Our findings suggest that Hfq can influence the growth of P. aeruginosa by limiting the toxic effects of specific MexT-regulated genes. Moreover, our results identify glutathione to be a factor important for the in vivo activity of MexT. IMPORTANCE Here we show that the conserved RNA chaperone Hfq is important for the growth of the opportunistic pathogen Pseudomonas aeruginosa. We found that the growth defect of hfq mutant cells is dependent upon the expression of genes that are under the control of the transcription regulator MexT. These include a gene that we refer to as hilR, which we show is negatively regulated by Hfq and encodes a small protein that can be toxic when ectopically produced in wild-type cells. Thus, Hfq can influence the growth of P. aeruginosa by limiting the toxic effects of MexT-regulated genes, including one encoding a previously unrecognized small protein. We also show that MexT activity depends on an enzyme that synthesizes glutathione.

scholarly journals 5-Lipoxygenase Negatively Regulates Th1 Response during Brucella abortus Infection in Mice

2015 ◽  
Vol 83 (3) ◽  
pp. 1210-1216 ◽  
Author(s):  
Júlia Silveira Fahel ◽  
Mariana Bueno de Souza ◽  
Marco Túlio Ribeiro Gomes ◽  
Patricia P. Corsetti ◽  
Natalia B. Carvalho ◽  
...  
Keyword(s):  
Brucella Abortus ◽  
Critical Role ◽  
Lipid Mediators ◽  
Negative Regulator ◽  
Host Responses ◽  
Interleukin 12 ◽  
Dependent Manner ◽  
Wild Type ◽  
Content Type ◽  
Deficient Mice

Brucella abortusis a Gram-negative bacterium that infects humans and cattle, causing a chronic inflammatory disease known as brucellosis. A Th1-mediated immune response plays a critical role in host control of this pathogen. Recent findings indicate contrasting roles for lipid mediators in host responses against infections. 5-Lipoxygenase (5-LO) is an enzyme required for the production of the lipid mediators leukotrienes and lipoxins. To determine the involvement of 5-LO in host responses toB. abortusinfection, we intraperitoneally infected wild-type and 5-LO-deficient mice and evaluated the progression of infection and concomitant expression of immune mediators. Here, we demonstrate thatB. abortusinduced the upregulation of 5-LO mRNA in wild-type mice. Moreover, this pathogen upregulated the production of the lipid mediators leukotriene B4and lipoxin A4in a 5-LO-dependent manner. 5-LO-deficient mice displayed lower bacterial burdens in the spleen and liver and less severe liver pathology, demonstrating an enhanced resistance to infection. Host resistance paralleled an increased expression of the proinflammatory mediators interleukin-12 (IL-12), gamma interferon (IFN-γ), and inducible nitric oxide synthase (iNOS) during the course of infection. Moreover, we demonstrated that 5-LO downregulated the expression of IL-12 in macrophages duringB. abortusinfection. Our results suggest that 5-LO has a major involvement inB. abortusinfection, by functioning as a negative regulator of the protective Th1 immune responses against this pathogen.

An adenylyl cyclase that functions during late development of Dictyostelium

Development ◽  
1999 ◽  
Vol 126 (23) ◽  
pp. 5463-5471 ◽  
Author(s):  
F. Soderbom ◽  
C. Anjard ◽  
N. Iranfar ◽  
D. Fuller ◽  
W.F. Loomis
Keyword(s):  
Adenylyl Cyclase ◽  
Critical Role ◽  
Fruiting Bodies ◽  
Wild Type ◽  
Adenylyl Cyclase Activity ◽  
Extracellular Signals ◽  
Mutant Strains ◽  
Morphological Mutants ◽  
Low Levels ◽  
Mutant Cells

A variety of extracellular signals lead to the accumulation of cAMP which can act as a second message within cells by activating protein kinase A (PKA). Expression of many of the essential developmental genes in Dictyostelium discoideum are known to depend on PKA activity. Cells in which the receptor-coupled adenylyl cyclase gene, acaA, is genetically inactivated grow well but are unable to develop. Surprisingly, acaA(−) mutant cells can be rescued by developing them in mixtures with wild-type cells, suggesting that another adenylyl cyclase is present in developing cells that can provide the internal cAMP necessary to activate PKA. However, the only other known adenylyl cyclase gene in Dictyostelium, acgA, is only expressed during germination of spores and plays no role in the formation of fruiting bodies. By screening morphological mutants generated by Restriction Enzyme Mediated Integration (REMI) we discovered a novel adenylyl cyclase gene, acrA, that is expressed at low levels in growing cells and at more than 25-fold higher levels during development. Growth and development up to the slug stage are unaffected in acrA(−) mutant strains but the cells make almost no viable spores and produce unnaturally long stalks. Adenylyl cyclase activity increases during aggregation, plateaus during the slug stage and then increases considerably during terminal differentiation. The increase in activity following aggregation fails to occur in acrA(−) cells. As long as ACA is fully active, ACR is not required until culmination but then plays a critical role in sporulation and construction of the stalk.

scholarly journals A Link between Arabinose Utilization and Oxalotrophy in Bradyrhizobium japonicum

2014 ◽  
Vol 80 (7) ◽  
pp. 2094-2101 ◽  
Author(s):  
Marion Koch ◽  
Nathanaël Delmotte ◽  
Christian H. Ahrens ◽  
Ulrich Omasits ◽  
Kathrin Schneider ◽  
...  
Keyword(s):  
Bradyrhizobium Japonicum ◽  
Host Plants ◽  
Root Nodule ◽  
Coenzyme A ◽  
Root Nodules ◽  
Proteome Analysis ◽  
Wild Type ◽  
Content Type ◽  
Mutant Cells ◽  
Respective Host

ABSTRACTRhizobia have a versatile catabolism that allows them to compete successfully with other microorganisms for nutrients in the soil and in the rhizosphere of their respective host plants. In this study,Bradyrhizobium japonicumUSDA 110 was found to be able to utilize oxalate as the sole carbon source. A proteome analysis of cells grown in minimal medium containing arabinose suggested that oxalate oxidation extends the arabinose degradation branch via glycolaldehyde. A mutant of the key pathway genesoxc(for oxalyl-coenzyme A decarboxylase) andfrc(for formyl-coenzyme A transferase) was constructed and shown to be (i) impaired in growth on arabinose and (ii) unable to grow on oxalate. Oxalate was detected in roots and, at elevated levels, in root nodules of four differentB. japonicumhost plants. Mixed-inoculation experiments with wild-type andoxc-frcmutant cells revealed that oxalotrophy might be a beneficial trait ofB. japonicumat some stage during legume root nodule colonization.

scholarly journals Candida albicans Morphogenesis Is Not Required for Macrophage Interleukin 1β Production

mBio ◽  
2012 ◽  
Vol 4 (1) ◽  
Author(s):  
Melanie Wellington ◽  
Kristy Koselny ◽  
Damian J. Krysan
Keyword(s):  
Transcription Factor ◽  
Candida Albicans ◽  
Interleukin 1Β ◽  
Inflammasome Activation ◽  
Wild Type ◽  
Content Type ◽  
Hypha Formation ◽  
Physical Presence ◽  
J774 Cells ◽  
Low Levels

ABSTRACTThe interaction ofCandida albicanswith macrophages induces the production of interleukin 1β (IL-1β) through inflammasome activation in a process that is required for host survival.C. albicanshypha formation has been linked to IL-1β production, but the question of whether hyphae are sufficient to trigger IL-1β production has not been examined directly. To address this question, aC. albicanslibrary of 165 transcription factor deletion mutants was screened for strains with altered IL-1β production by lipopolysaccharide (LPS)-primed J774 cells, a murine macrophage-like cell line. Eight mutants with decreased and two mutants with increased IL-1β secretion were identified. In addition, 12 mutants with previously identified morphology deficits were found to induce IL-1β secretion to levels similar to those of the wild type. Examination of the morphology of both low and normal IL-1β-inducing mutants in macrophages revealed that two mutants (upc2Δ/upc2Δ andahr1Δ/Δ mutants) were indistinguishable from the wild type with respect to morphology yet induced low levels of IL-1β; conversely, thendt80Δ/Δ mutant was deficient for hypha formation but induced levels of IL-1β similar to those of the wild type. Transcription factor mutants deficient for IL-1β secretion also caused markedly lower levels of macrophage lysis. Similarly, the ability of a mutant to cause macrophage lysis was independent of its ability to form hyphae. Taken together, our observations indicate that the physical formation of hyphae is not sufficient to trigger IL-1β secretion or macrophage lysis and suggest that other mechanisms, such as pyroptosis, a caspase-1-dependent response to intracellular pathogens, may play a role in the interaction of macrophages withC. albicans.IMPORTANCEThe ability ofCandida albicansto transition from yeast to filamentous cells plays an important and complex role in pathogenesis. Recent results from a number of investigators indicate that the host responds to yeast and hyphalC. albicansdifferently. For example, aC. albicansmutant unable to form hyphae also fails to induce interleukin 1β (IL-1β) secretion from macrophages. We have identifiedC. albicanstranscription factor mutants that have decreased IL-1β secretion but retain the ability to form hyphae in response to macrophages. In addition, these mutants cause significantly less macrophage lysis. These observations indicate that the physical presence of the hyphal structure in the macrophage is not sufficient to trigger IL-1β secretion nor does it cause physical lysis of the cell. Our data indicate that characteristics of hyphae separate from its physical morphology are responsible for triggering the release of IL-1β release and causing macrophage lysis. Since these observations are inconsistent with some current models, alternative mechanisms for the interaction ofC. albicanswith macrophages must be considered.

scholarly journals Salmonella enterica Serovar Typhimurium NiFe Uptake-Type Hydrogenases Are Differentially Expressed In Vivo

2008 ◽  
Vol 76 (10) ◽  
pp. 4445-4454 ◽  
Author(s):  
Andrea L. Zbell ◽  
Susan E. Maier ◽  
Robert J. Maier
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Acid Stress ◽  
Wild Type ◽  
Reverse Transcription Pcr ◽  
Serovar Typhimurium ◽  
Low Levels ◽  
And Function ◽  
Mutant Cells

ABSTRACT Salmonella enterica serovar Typhimurium, a common enteric pathogen, possesses three NiFe uptake-type hydrogenases. The results from mouse infection studies suggest that the H2 oxidation capacity provided by these hydrogenases is important for virulence. Since the three enzymes are similar in structure and function, it may be expected that they are utilized under different locations and times during an infection. A recombination-based method to examine promoter activity in vivo (RIVET) was used to determine hydrogenase gene expression in macrophages, polymorphonuclear leukocyte (PMN)-like cells, and a mouse model of salmonellosis. The hyd and hya promoters showed increased expression in both murine macrophages and human PMN-like cells compared to that in the medium-only controls. Quantitative reverse transcription-PCR results suggested that hyb is also expressed in phagocytes. A nonpolar hya mutant was compromised for survival in macrophages compared to the wild type. This may be due to lower tolerance to acid stress, since the hya mutant was much more acid sensitive than the wild type. In addition, hya mutant cells were internalized by macrophages the same as wild-type cells. Mouse studies (RIVET) indicate that hyd is highly expressed in the liver and spleen early during infection but is expressed poorly in the ileum in infected animals. Late in the infection, the hyd genes were expressed at high levels in the ileum as well as in the liver and spleen. The hya genes were expressed at low levels in all locations tested. These results suggest that the hydrogenases are used to oxidize hydrogen in different stages of an infection.

scholarly journals The H3K27me3 Demethylase dUTX Is a Suppressor of Notch- and Rb-Dependent Tumors in Drosophila

2010 ◽  
Vol 30 (10) ◽  
pp. 2485-2497 ◽  
Author(s):  
Hans-Martin Herz ◽  
Laurence D. Madden ◽  
Zhihong Chen ◽  
Clare Bolduc ◽  
Eugene Buff ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Histone H3 ◽  
Epigenetic Mark ◽  
Dependent Manner ◽  
Wild Type ◽  
Independent Manner ◽  
Jmjc Domain ◽  
Mutant Cells ◽  
Excessive Activation

ABSTRACT Trimethylated lysine 27 of histone H3 (H3K27me3) is an epigenetic mark for gene silencing and can be demethylated by the JmjC domain of UTX. Excessive H3K27me3 levels can cause tumorigenesis, but little is known about the mechanisms leading to those cancers. Mutants of the Drosophila H3K27me3 demethylase dUTX display some characteristics of Trithorax group mutants and have increased H3K27me3 levels in vivo. Surprisingly, dUTX mutations also affect H3K4me1 levels in a JmjC-independent manner. We show that a disruption of the JmjC domain of dUTX results in a growth advantage for mutant cells over adjacent wild-type tissue due to increased proliferation. The growth advantage of dUTX mutant tissue is caused, at least in part, by increased Notch activity, demonstrating that dUTX is a Notch antagonist. Furthermore, the inactivation of Retinoblastoma (Rbf in Drosophila) contributes to the growth advantage of dUTX mutant tissue. The excessive activation of Notch in dUTX mutant cells leads to tumor-like growth in an Rbf-dependent manner. In summary, these data suggest that dUTX is a suppressor of Notch- and Rbf-dependent tumors in Drosophila melanogaster and may provide a model for UTX-dependent tumorigenesis in humans.

scholarly journals Analysis of the Borrelia burgdorferi Cyclic-di-GMP-Binding Protein PlzA Reveals a Role in Motility and Virulence

2011 ◽  
Vol 79 (5) ◽  
pp. 1815-1825 ◽  
Author(s):  
Joshua E. Pitzer ◽  
Syed Z. Sultan ◽  
Yoshihiro Hayakawa ◽  
Gerry Hobbs ◽  
Michael R. Miller ◽  
...  
Keyword(s):  
Life Cycle ◽  
Borrelia Burgdorferi ◽  
Binding Protein ◽  
Survival Rates ◽  
Wild Type ◽  
Content Type ◽  
Infectious Dose ◽  
Swimming Pattern ◽  
Bacteria Inactivation ◽  
Mutant Cells

ABSTRACTThe cyclic-dimeric-GMP (c-di-GMP)-binding protein PilZ has been implicated in bacterial motility and pathogenesis. Although BB0733 (PlzA), the only PilZ domain-containing protein inBorrelia burgdorferi, was reported to bind c-di-GMP, neither its role in motility or virulence nor it's affinity for c-di-GMP has been reported. We determined that PlzA specifically binds c-di-GMP with high affinity (dissociation constant [Kd], 1.25 μM), consistent withKdvalues reported for c-di-GMP-binding proteins from other bacteria. Inactivation of the monocistronically transcribedplzAresulted in an opaque/solid colony morphology, whereas the wild-type colonies were translucent. While the swimming pattern of mutant cells appeared normal, on swarm plates, mutant cells exhibited a significantly reduced swarm diameter, demonstrating a role ofplzAin motility. Furthermore, theplzAmutant cells were significantly less infectious in experimental mice (as determined by 50% infectious dose [ID50]) relative to wild-type spirochetes. The mutant also had survival rates in fed ticks lower than those of the wild type. Consequently,plzAmutant cells failed to complete the mouse-tick-mouse infection cycle, indicatingplzAis essential for the enzootic life cycle ofB. burgdorferi. All of these defects were corrected when the mutant was complemented incis. We propose that failure ofplzAmutant cells to infect mice was due to altered motility; however, the possibility that an unidentified factor(s) contributed to interruption of theB. burgdorferienzootic life cycle cannot yet be excluded.

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