Dissertations / Theses on the topic 'Negative regulators'
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Lively, Julie C. (Julie Christina) 1971. "Beta 3 integrins : negative regulators of angiogenesis." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8386.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Biology, 2002.Includes bibliographical references (leaves 199-219).
A method was developed to isolate and purify primary murine endothelial cells from lung tissue (MLEC). The cells generated by this method were characterized by immuno-fluorescence detection and FACS analysis and expressed specific antigens including PECAM-1, ICAM-1, ICAM-2, VCAM-1 and VE-cadherin. Using this method, cells from wild-type and beta 3-integrin-deficient animals were purified and used to determine the specificity of a novel potential anti-angiogenic drug. This study shows that tumstatin, a fragment of the alpha 3 chain of collagen IV, inhibits proliferation, inhibits total protein synthesis and specifically inhibits CAP-dependent protein synthesis in MLEC. These effects do not occur when beta 3-null MLEC are treated with tumstatin or any of its derivatives. Nor do they occur in mouse embryonic fibroblasts which do express beta 3 integrin. The inhibition by tumstatin also occurs in in vivo angiogenesis assayed using a Matrigel plug insert. Similarly to in vitro assays, tumstatin failed to inhibit angiogenesis in beta 3 integrin-deficient animals. These results suggest that avf33 integrin is necessary but not sufficient for the activity of tumstatin. Further studies are required to identify avf33 integrin-associated factors in endothelial cells which determine tumstatin's endothelial cell specificity. Matrigel plug assays were also used to demonstrate that the loss of beta-3 integrin enhanced VEGF-induced angiogenesis. Results also show that VEGF-induced angiogenesis was enhanced in aortic ring explants from beta 3-null animals. These data suggest a new role for beta 3 integrin as a negative regulator of angiogenesis, both as a receptor for an endogenous inhibitory molecule and as an inhibitor of VEGF-induced angiogenesis.
by Julie C. Lively.
Ph.D.
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Kearns, Jeffrey D. "Distinct functions of negative regulators of NF-kappaB." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3360060.
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Thesis (Ph. D.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed August 11, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 197-205).
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Datar, Ila. "Positive and negative regulators of tumorigenesis and/or metastasis." University of Toledo Health Science Campus / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=mco1438962728.
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Subedee, Ashim. "Molecular Determinants and Transcriptional Regulators in Triple Negative Breast Cancer." Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:23845415.
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Breast cancer is a highly heterogeneous disease with differences in histopathological and biological characteristics, variable prognoses, and response to therapy. Clinically, breast
tumors are classified based on the expression of hormone receptors (ER and PR) and HER2 as hormone receptor positive (ER+, PR+), HER2+, and triple negative (ER-, PR-, HER2-). Based
on gene expression profiling, breast cancers have been classified into luminal (luminal A and B), HER2+, basal-like and claudin-low subtypes. Knowledge of the molecular properties of luminal and HER2+ subtypes has led to the development of endocrine and HER2-targeted therapies. However, the molecular determinants and transcriptional regulators of basal-like tumors that constitute the majority of triple negative breast cancer (TNBC) are poorly understood. In this dissertation, we have defined some of the molecular characteristics of the basal-like breast cancer phenotype and also identified multiple transcriptional regulators specific to TNBCs.
By using three different reprogramming approaches – somatic cell fusion, nuclear
reprogramming, and transcription factor transduction, we showed that the basal-like breast cancer phenotype is generally dominant and is largely defined by epigenetic repression of luminal transcription factors. We found that luminal breast cancers share a common core epigenetic program, whereas basal-like breast cancers are highly heterogeneous. We demonstrated that protein extracts of basal-like breast cancer cells can reprogram a subset of
luminal breast cancer cells to a basal-like state. Additionally, we identified three transcription factors, EN1, TBX18, and TCF4, the overexpression of which induced the repression of some
luminal features in luminal breast cancer cells.
We also performed a targeted cellular viability screen for selected transcription factors differentially expressed between triple negative and other breast cancer subtypes and identified multiple factors essential for TNBCs including EN1 and TRIP13. We found that downregulation of EN1 and TRIP13 preferentially and significantly reduce cellular viability, colony formation, and in vivo tumorigenicity of TNBC cell lines. We demonstrated that downregulation of EN1 induces an arrest in the G1 phase of the cell cycle and apoptosis. By analyzing the gene expression and histone H3 lysine 27 acetylation (H3K27ac) profiles of TNBC cell lines following downregulation of EN1, we found that EN1 regulates genes involved in angiogenesis, neurogenesis, cell matrix interactions, and WNT signaling pathways. We also performed ChIP-seq for exogenously expressed HA-tagged EN1 to identify its genomic targets. Lastly, we showed that the expression of EN1 correlates with shorter overall survival among patients with basal-like breast tumors. Similarly, by analyzing the gene expression profiles of TNBC cell lines following downregulation of TRIP13, we found that TRIP13 regulates genes involved in IL6 signaling, cell proliferation, and angiogenesis; in line with this we confirmed reduced levels of JAK2 and phospho-STAT3 following TRIP13 downregulation.
In summary, we have unraveled some of the molecular mechanisms of basal-like and luminal breast cancer cell phenotypes and identified factors that might repress luminal differentiation programs in basal-like breast tumors. We have also identified multiple triple negative breast cancer specific transcription regulators. We believe these studies have increased our molecular understanding of basal-like and triple negative breast cancers and have provided potential therapeutic targets for these breast tumors.Medical Sciences
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Carlsson, Emil Karl Viktor. "Biochemical, molecular and cellular studies on negative regulators of TLR-signalling." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/38528.
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Toll-like receptors (TLRs) recognise pathogenic microorganisms through conserved pathogen associated molecular patterns, which activates the innate immune response. TLR signalling is mediated by cytoplasmic adaptor proteins via Toll/interleukin-1 receptor (TIR) domains. Sterile α- and armadillo-motif-containing protein (SARM) is the fifth TLR adaptor protein identified in humans and has been described as a negative regulator of the innate immune response. Several pathogenic bacteria are also known to express proteins with TIR- domains, which are believed to be involved in disruption of TLR signalling. This raises the question of whether SARM functions in a similar manner, as phylogenetic studies have shown that SARM is closely related to bacterial proteins. In this project, functional characterisation of SARM and a bacterial TIR domain protein from Bacillus anthracis (BaTdp) have been performed using both recombinantly expressed and purified proteins, as well as cellular assays. The TIR domains of both SARM and BaTdp were found to form heterotypic TIR-TIR interactions with multiple human TLR adaptors, including Myeloid differentiation factor 88 (MyD88). SARM and MyD88 both localised to mitochondria when overexpressed in mammalian cells, and SARM overexpression was associated with a reduction of TLR2-, TLR4- and MyD88- induced cytokine activation. A single amino acid residue in the SARM BB-loop motif, G601, was also identified as being critical for SARM's anti-inflammatory effect. A short peptide derived from this motif was able to target MyD88 in vitro and slightly reduce TLR4-mediated cytokine activation. Overexpression of BaTdp in mammalian cells had no significant effect on TLR-mediated cytokine activation. Instead, the protein targeted microtubular networks in the cell and BaTdp expression was associated with a significant increase in cellular autophagy activity. The findings further enhance our understanding of the underlying mechanisms by which SARM suppress the innate immune response, and also describe previously unknown functions of BaTdp.
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Spencer, William John. "Negative regulators of chromosome replication in the dimorphic bacterium Caulobacter crescentus." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103183.
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Caulobacter crescentus provides an accessible system for investigating the regulation of chromosome replication and cellular development. The Caulobacter cell cycle produces a free-swimming swarmer cell and a sessile stalk cell. In swarmer cells, chromosome replication is selectively repressed while stalk cells are committed to chromosome replication.In Caulobacter, chromosome replication is repressed, in part, by the binding of the response regulator CtrA to five binding sites (a-e) within the Caulobacter origin of replication (Cori ). Periodic phosphorylation of CtrA stimulates binding to the consensus sequence TTAA-N7-TTAA (N= any nucleotide) found in Cori and many cell-cycle regulated genes. This thesis presents an alternate mode of CtrA binding, namely, that phosphorylation does not stimulate binding to a specific class of CtrA-regulated promoters. This work shows that CtrA and CtrA-phosphate bind to two ctrA promoters with equal and weak affinity. As well, in vivo binding assays reveal that a non-proteolyzable CtrA allele (CtrADelta3) can occupy the ctrA promoters continuously without altering the temporal regulation of these promoters. The data suggest phosphorylation, while not increasing affinity for weak CtrA binding sites, provides allosteric signals that permit the recruitment of components required for transcription.
The proposed allosteric mechanism of CtrA-regulated transcription may also be important for CtrA-mediated repression of chromosome replication. Chromatin Immunoprecipitation assays (ChIP) allow for the sensitive detection of specific protein/DNA complexes in vivo. ChIP reveals that CtrA binds to Cori in swarmers but not in stalk cells when chromosome replication commences. The protein chaperone, ClpX, was recruited to Cori prior to the start of S-phase and correlates with the loss of CtrA binding to Cori. Expression of a non-proteolyzable CtrADelta3 allele showed increased affinity for Cori DNA. The increase in CtrADelta3 binding stimulated a corresponding increase in C1pX binding to Cori. This evidence suggests that C1pX recruitment to Cori is likely CtrA-dependant. The absence of CtrA binding in stalk cells suggests other mechanisms may be required to prevent re-replication in stalk cells.
An analysis of the Caulobacter genome identifies two DnaA-like genes. The first, cdl-1, is a homolog of the E. coli hda gene, a protein essential for regulated inactivation of DnaA (RIDA). The second, cdl-2, is a novel gene restricted to the alpha-proteobacteria group and whose function is unknown. Overexpression of either gene in Caulobacter produced filamentous cells that could not divide. DNA synthesis in these cells is also impaired and suggests the intracellular concentrations of these two proteins are important for coordinating proper cell cycle progression.
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Hooker, Erika. "Negative regulators of the Src family kinases in renal epithelial cells." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116932.
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The Src kinases are non-receptor tyrosine kinases involved in many epithelial processes in both normal and injured cells. Src was originally identified as a viral oncogene and has since been characterized as an important regulator of cellular proliferation, differentiation, and motility. Our lab has previously demonstrated that the Src kinases are important modifiers of gene expression in tubule cells of the kidney during ischemia-reperfusion injury. The signalling events that control and mediate the Src kinase transcriptional response in renal epithelial cells are not well understood. In this thesis, I have identified two novel negative regulators of the Src transcriptional response in renal epithelial cells. In Manuscript I and II, I demonstrate that the adapter protein Dok-4 can act as an inhibitor of Src-mediated transcription. Unlike most other adapter proteins, several members of the Dok family are primarily characterized by their inhibitory actions downstream of active tyrosine kinases. Despite being the most ubiquitously expressed Dok family member, Dok-4 function has remained elusive as few interacting proteins have been identified. In Manuscript I, we found that the previously defined boundaries of the Dok-4 PTB domain needed to be extended for proper function. We demonstrate that the PTB domain of Dok-4 contains an extended C-terminal alpha helix critical for canonical PTB-mediated interaction and identified the lipid phosphatase Ship1 as a novel partner of this redefined Dok-4 PTB domain. This interaction is greatly increased in the presence of active Src kinases and occurs through a canonical NPXpY motif present in the C-terminal region of Ship1. In contrast to the Dok-4-Ship1 interaction, in Manuscript II we present a non-canonical PTB-mediated interaction between Dok-4 and the nuclear transcription factor, Elk4. This interaction leads to relocalization of Elk4 from the nucleus to the cytoplasm and degradation of full-length Elk4. In renal cells, Dok-4 inhibits Src-mediated activation of Elk4 and represses expression of the immediate early genes, such as egr-1 and fos1, as well as some of their transcriptional targets. In agreement with this data, knock-down of Dok-4 was associated with increased proliferation of renal epithelial cells. During renal ischemia-reperfusion injury, where upregulation of immediate early genes is known to occur, we have for the first time detected a strong activation of the Src kinases and a delayed upregulation of Elk4, suggesting that Elk4 may be not only highly expressed, but also highly active. Dok-4, which is expressed in the kidney, may be essential for limiting damage to the kidney caused by Elk4-induced expression of the immediate early genes. In addition to activating transcription of the immediate early genes, we have previously shown that the Src kinases are responsible for transcriptionally upregulating the receptor tyrosine kinase, EphA2, during renal ischemia-reperfusion injury. In the preliminary manuscript presented here, we observed that while the Src kinases are highly active, the Stat proteins, downstream effectors of the Jak kinases, are dephosphorylated and inactive. As a corollary of this observation, overexpression of all three ubiquitous Jak family members, Jak1, Jak2 and Tyk2 could attenuate Src-mediated activation of the EphA2 promoter. Inhibition of endogenous Jak kinase by siRNA-mediated knock-down or incubation with the pharmacological inhibitor, Jak inhibitor I also activated EphA2 transcription. Surprisingly, Jak-mediated inhibition of EphA2 expression occurs independently of the Stat family and the cytokine receptors. Collectively, this thesis identifies two novel regulators of the Src kinase family in renal epithelial cells, the Dok-4 adapter protein and the family of Jak kinases.Les kinases Src sont des tyrosine-kinases cytosoliques qui sont impliquées dans multiples processus dans les cellules épithéliales et autres. Originalement identifiée comme un oncogène viral, la kinase Src est maintenant caractérisée comme une régulatrice de la prolifération, la différenciation et la motilité cellulaire. Nous avons précédemment montré que les kinases Src sont capables de modifier l'expression génique dans les tubules des reins durant le domage rénal par ischémie et réperfusion. Cependant, les mécanismes de signalisation qui contrôle la réponse transcriptionelle des kinases Src ne sont pas bien compris. La présente thèse décrit deux nouveaux inhibiteurs endogènes de la famille de kinases Src dans les cellules rénale épithéliales.Les deux premiers manuscrits établissent que la protéine adaptatrice Dok-4 fonctionne comme un inhibiteur des kinases Src. Contrairement à la plus part de protéines adaptatrices, la famille Dok est caractérisée par des actions inhibitrices durant la signalisation par les tyrosines kinases. Malgré que Dok-4 soit le membre de la famille Dok exprimé de manière la plus ubiquitaire, sa fonction est encore mal connue. Le premier manuscrit que je présente (Manuscrit I) décrit le domaine PTB de Dok-4. On y a démontré que le domaine PTB contient une extension C-terminal consistant probablement en une hélice alpha et que celle-ci est essentielle pour les interactions canoniques du domaine PTB de Dok-4. De plus, nous avons identifié la phosphatase lipidique Ship1 comme un nouveau partenaire de ce domaine PTB redéfini. Cette interaction est augmentée quand les kinases Src sont actives et elle implique un motif NPXpY dans la région C-terminale de Ship1. Contrairement à l'interaction entre Dok-4 et Ship1, l'interaction décrite dans le deuxième manuscrit (Manuscrit II) entre Dok-4 et le facteur de transcription, Elk4, implique le domaine PTB, mais se fait dans une manière atypique. L'interaction entre Dok-4 et Elk4 induit la relocalisation d'Elk4 du noyau au cytoplasme et cause la dégradation de la protéine Elk4. Dans les cellules rénales, Dok-4 inhibe l'activation d'Elk4 par les kinases Src et réprime l'expression des gènes de réponse précoce ("immediate early genes"), comme egr-1 et fos, et quelques cibles transcriptionelles de ces gènes. En accord avec ces données, suppression de Dok-4 est associée avec une augmentation de prolifération. En utilisant un modèle in vivo d'ischémie-reperfusion rénale, où la surexpression de gène de réponse précoce a déjà été démontrée, nous avons détecté une forte activation des kinases Src suivie d'une augmentation retardée de l'expression d'Elk4 dans les lysates de reins. Ces données suggèrent que dans ce modèle Dok-4 pourrait être critique pour limiter les dommages aux reins causé par l'induction des gènes de réponse précoce par Elk4. En plus d'activer l'expression des gènes de réponse précoce, nous avons précédemment montré que les kinases Src sont impliquées dans l'induction transcriptionnelle du récepteur tyrosine-kinase, EphA2, durant l'ischémie-reperfusion rénale. Dans le manuscrit préliminaire que je présente, nous avons noté que dans un modèle de déplétion et réplétion d'ATP, les kinases Src sont activées et les protéines Stat, des effecteurs des kinases Jak, sont déphsophorylés et inactives. Comme corollaire de cette observation, la surexpression de trois membres de de la famille Jak inhibent l'activation du promoteur d'EphA2 par les Src kinases. En plus, l'inhibition des kinases Jak endogènes par traitement aux siRNA ou par un inhibiteur pharmacologique, Jak Inhibitor I, active le promoteur d'EphA2. Étonnement, l'inhibition de l'expression d'EphA2 par les kinases Jak se fait indépendamment des protéines Stat et les récepteurs à cytokines. Mises ensemble, les données de cette thèse démontrent deux nouveaux inhibiteurs de la famille Src dans les cellules rénales épithéliales, la protéine adaptatrice, Dok-4 et les kinases, Jak1 et Jak2.
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Evans, Abigail Alexandra. "An analysis of selected negative regulators of growth in breast cancer." Thesis, Queen Mary, University of London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287979.
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Gadbois, Ellen L. (Ellen Louise) 1968. "Functional antagonism of the RNA polymerase II holoenzyme by negative regulators." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43553.
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Miller, Allan. "Negative regulators of gene expression in yeast : a1/α2 and SIR." Thesis, University of Cambridge, 1987. https://www.repository.cam.ac.uk/handle/1810/270426.
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Dierdorf, Nina [Verfasser]. "Identification of negative regulators of integrin-mediated cell adhesion / Nina Dierdorf." Konstanz : Bibliothek der Universität Konstanz, 2015. http://d-nb.info/1142113876/34.
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Black, Markaisa. "FOX proteins as novel negative regulators of lung fibrosis and mitochondrial respiration." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1530270199796482.
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Wilson, Robert. "Characterisation of XId2 and XId4, putative negative regulators of HLH genes in Xenopus laevis." Thesis, Open University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357135.
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Maehr, Tanja. "Cloning and expression analysis of putative negative regulators of immune responses in rainbow trout Oncorhynchus mykiss." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=201702.
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A more detailed understanding of the immune mechanisms involved in anti-inflammatory events in fish is required for effective disease control in aquaculture. Significant expansion of immune genes, often resulting from whole genome duplication events in teleost fish, adds complexity to their potentially anti-inflammatory pathways. This thesis contributes to a more complete insight into the suppressor of cytokine signalling (SOCS) and transforming growth factor-β1 (TGF-β1) gene system in fish by the discovery of paralogues and reporting of ways in which these potential negative regulators of immune responses can be induced in the the commercially valuable rainbow trout (Oncorhynchus mykiss). Gene expression analysis, revealed that a novel trout TGF-β1 paralogue (TGF-β1b) was more inducible by immune stimulants than the known TGF-β1a and likely represents an important intrinsic factor in macrophages. Both trout TGF-β type I and type II receptor (TGFBR1 and TGFBR2) genes identified encode highly conserved serine/threonine kinases and they are modulated during immune responses. Counter-regulation of the two receptor transcripts in immune stimulated macrophages may indicate regulatory mechanisms operating at the receptor level. Thorough phylogenetic and synteny analysis of the lower vertebrate SOCS system led to further paralogue discovery and uncovered that the proposed teleost-specific SOCS-8 and SOCS-9 members are more likely paralogues of cytokine inducible SH2-containing protein (CISH) and SOCS-5. The trout SOCS-2 subfamily was expanded to three members by cloning SOCS-2b and SOCS-2bRel in addition to SOCS-2a. I revealed for the first time that four paralogues in a SOCS subfamily exist in a teleost by cloning trout CISHa2, CISHb1 and CISHb2 in addition to the known CISHa1. In vivo and in vitro expression of the CISH paralogues suggest possible subfunctionalisation in immunity and development. Attempts to produce trout recombinant proteins of potentially anti-inflammatory cytokines in transiently transfected mammalian cells primed exploitation of these molecules in functional studies.
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Amin, Parth Hitenbhai, and Parth Amin. "Adducins are Negative Regulators of Migration and Invasion of Normal Lung Epithelial Cells and Lung Cancer Cells." VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4401.
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Cell migration is an important component of many physiological and pathological processes such as tissue and organ morphogenesis during development, wound healing, inflammatory immune response, and tumor metastasis. The actin cytoskeleton is the basic engine driving cell migration. In the present study, we elucidate the role of an important actin interacting proteins, Adducins, in motility of normal lung epithelium and lung cancer cells. Adducins are the family of cytoskeleton protein capping the fast growing end and facilitating the bundling of actin filaments. Adducins are encoded by the three closely related genes namely alpha (ADD1), beta (ADD2) and gamma (ADD3) Adducin. ADD1 and ADD3 are ubiquitously expressed, whereas ADD2 is most abundant in brain and erythrocytes. Adducins are also involved in recruiting spectrin to the actin filaments forming spectrin-actin membrane skeletal network. Its role in cell motility remains controversial. In this study, we observed that CRISPR/Cas9 mediated stable knockout of ADD1 and ADD3 in 16HBE normal lung epithelium cells significantly increases transfilter migration of cells. On the other hand, stable overexpression of ADD1 in H1299 Non-Small Cell lung cancer cells significantly decreases wound healing, transfilter migration and Matrigel invasion of the cells. Importantly, the effects of Adducin depletion and overexpression on cell motility were not due to altered cell proliferation. ADD1 overexpressed H1299 cells were characterized by the increased adhesion and spreading on the collagen matrix. Fluorescence microscopy revealed alterations in their cortical actin cytoskeleton that was manifested in the assembly of peripheral F-actin bundles and formation of filopodia-like protrusions. These findings suggest that Adducins are negative regulators of motility of normal lung epithelial and lung cancer cells that act by altering the architecture of submembranous actin cytoskeleton and modulating cell adhesion to the extracellular matrix.
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Jameson, Katie H. "Structural and biophysical investigations of two negative regulators of DNA replication initiation in Bacillus subtilis, YabA and SirA." Thesis, University of York, 2015. http://etheses.whiterose.ac.uk/13168/.
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DNA replication initiation is strictly controlled to maintain chromosome copy number. Over- or under-replication of an organism's genome is detrimental to survival, thus initiation events are tightly regulated to ensure only one round of DNA replication occurs per cell cycle. In prokaryotes, DNA replication commences when a protein initiator, DnaA, forms a helical filament at the origin of replication, oriC, inducing localised DNA unwinding and the recruitment of the replication machinery. The work described here sought to elucidate how DNA replication initiation is regulated in the Gram-positive model organism Bacillus subtilis. In particular, this work aimed to offer insight into the mechanisms of two negative regulators of DNA replication initiation, SirA and YabA; proteins that play significant roles in regulating replication initiation in sporulating and vegetatively growing cells, respectively. Both SirA and YabA interact directly with the initiator DnaA, and YabA has additionally been shown to interact with the DNA polymerase β-clamp, DnaN (an essential component of the replication machinery). Detailed here are structural and biophysical studies of SirA and YabA. This includes the X-ray crystal structure of SirA bound to the N-terminal domain of DnaA in an inhibitory complex, and characterisation of the SirA-DnaADI interface using an in vitro assay. When coupled with in vivo localisation studies carried out by our collaborators, the work on SirA suggests a mechanism for its inhibition of DNA replication. Also detailed are biophysical studies used to characterise the architecture of YabA, guided by the use of in silico models, and the X-ray crystal structure of YabA's N-terminal domain. These results are discussed alongside structural and mutational studies of YabA carried out by our collaborators; collectively the results delineate the full-length structure of YabA and offer insight into its interactions with DnaA and DnaN.
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Li, Zhi. "Insights on type I IFN signaling and regulation : studies of disease-associated TYK2 variants and of the negative regulators USP18/ISG15." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066437/document.
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L'action ubiquitaire de l'interféron de type I (IFN- alpha/beta , ici IFN) dans la physiologie et la pathologie est aujourd'hui certaine. Une réponse dérégulée à l'IFN peut entraîner des interféronopathies ou des maladies auto-immunes. Dans mon travail de thèse j'ai étudié trois éléments de la voie de signalisation de l'IFN afin de comprendre comment une dérégulation peut se produire. TYK2 est une tyrosine kinase de la famille Janus impliquée dans la signalisation de cytokines immunorégulatrices (IFN de type I, IL-10, IL-12, IL-23). Selon le récepteur, TYK2 est co-activé avec JAK1 ou JAK2. L'interaction moléculaire entre les deux kinases juxtaposées est peu connue. J'ai caractérisé deux variants de TYK2 associés à des maladies auto-immunes, TYK2 I684S et TYK2 P1104A. J'ai démontré que ces deux variants ont un défaut catalytique, mais soutiennent la réponse à l'IFN. Mes résultats suggèrent un modèle d'activation réciproque des deux kinases. Par des études de signalisation dans les cellules EBV-B j'ai montré que l'homozygotie TYK2 P1104A a un impact différent selon la cytokine étudiée. L'analyse de deux autres polymorphismes de TYK2 associés à des maladies auto-immunes (rs12720270, rs2304256) a montré un impact sur la rétention de l'Exon 8, ce qui augmente l'expression de TYK2. J'ai aussi contribué à la dissection du mécanisme moléculaire contrôlant la réponse à l'IFN dans les cellules de patients déficients pour USP18 ou ISG15 et souffrant d'interféronopathies. Ces travaux ont démontré le rôle essentiel d'USP18 pour restreindre la réponse à l'IFN et ont mis en évidence ISG15 comme un nouvel inhibiteur de l'IFN chez l'humain mais pas chez la sourisToday, the pervasive action of type I IFN (IFN-alpha/beta, here IFN) in human physiology and pathology has become evident. Dysregulated IFN response can lead to interferonopathies and auto-immune diseases (AID). My thesis work has focused on the study of three elements of the IFN response pathway, aiming to understand how dysregulation occurs. TYK2 belongs to the Janus tyrosine kinase family and is involved in signaling of several immunoregulatory cytokines, such as type I IFN, IL-10, IL-12 and IL-23. Depending on the receptor complex, TYK2 is co-activated with either JAK1 or JAK2. A detailed molecular characterization of the interplay between the two juxtaposed enzymes is missing. In my study, I characterized two rare AID-associated human variants TYK2 I684S and TYK2 P1104A. I found that both variants are catalytically impaired but rescue signaling in response to IFN in fibroblasts. My results support a model of reciprocal activation of Janus kinases. Through signaling studies I showed that TYK2 P1104A homozygosity has a cytokine-specific impact in EBV-B cells. My studies of two other AID-associated TYK2 SNPs (rs12720270 and rs2304256) suggest that they promote Exon 8 retention and increase TYK2 expression. In the second part of my thesis work, I contributed to dissecting the molecular mechanism that tunes down IFN response in cells from rare USP18- and ISG15-deficient patients that suffered of interferonopathies. This work substantiated the essential role of USP18 in downregulating the IFN response and highlighted ISG15 as a novel IFN inhibitor in humans, but not in mice
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Nilsson, Jonas. "The LRIG-family : identification of novel regulators of ErbB signaling with clinical implications in astrocytoma /." Doctoral thesis, Umeå : Department of Radiation Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-783.
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Nunes, de Miranda Susana Marina Verfasser], Michael [Akademischer Betreuer] Huber, and Ralph [Akademischer Betreuer] [Panstruga. "Influence of the two negative regulators SHIP1 and Lyn on the antigen-induced mast cell phenotype / Susana Marina Nunes de Miranda ; Michael Huber, Ralph Panstruga." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1171993285/34.
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Nunes, de Miranda Susana Marina [Verfasser], Michael Akademischer Betreuer] Huber, and Ralph [Akademischer Betreuer] [Panstruga. "Influence of the two negative regulators SHIP1 and Lyn on the antigen-induced mast cell phenotype / Susana Marina Nunes de Miranda ; Michael Huber, Ralph Panstruga." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1171993285/34.
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Neubauer, Svetlana. "Untersuchungen von inter- und intramolekularen Interaktionen des globalen Regulators AbrB und dessen Antirepressors AbbA." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://dx.doi.org/10.18452/16887.
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Aus den frühen Bindungsstudien des globalen Regulators AbrB mit der ausgedehnten phyC-Promotorregion von Bacillus amyloliquefaciens FZB45 konnte ein mehrstufiger kooperativer Bindungsprozess abgeleitet werden. Dabei verlangt die AbrB-vermittelte Repression von phyC nach Integrität zweier großer Bindungsstellen, ABS1 und ABS2, die 162 bp voneinander entfernt liegen. In der vorliegenden Arbeit wurden die ersten Echtzeitkinetiken zur DNA-AbrB-Interaktion mittels der Oberflächenplasmonresonanz (SPR) gemessen und analysiert. AbrB zeigte hohe Affinitäten zu den 40 bp langen Oligonukleotiden, die den beiden Bindungsstellen entstammen. Dabei verursachten alle Oligonukleotide der ABS2 und nur eine kurze Region innerhalb der ABS1 bei der Bindung von AbrB Konformationsänderungen im Protein und in der DNA (CD - Zirkulardichroismusspektroskopie) und wiesen eine Kooperativität von 2In previous binding studies it could be demonstrated that a global regulator AbrB and the extensive phyC promoter region of Bacillus amyloliquefaciens FZB45 interact in a complex manner. AbrB binding is a multistep cooperative process. The integrity of both binding sites, ABS1 and ABS2, which are separated by 162 bp, is crucial for the AbrB-mediated repression of phyC. This work presents the first real-time binding kinetics of the AbrB-DNA interaction using surface plasmon resonance (SPR). AbrB exhibited high affinities to all analyzed 40-bp oligonucleotides that were derived from the ABSs of phyC. All parts of the ABS2, but only a small region within ABS1, were bound cooperatively to AbrB with a stoichiometry of 2 DNA to 1 AbrB tetramer and with 2
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Lei, Ernest. "Cascaded Linear Regulator with Negative Voltage Tracking Switching Regulator." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2176.
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DC-DC converters can be separated into two main groups: switching converters and linear regulators. Linear regulators such as Low Dropout Regulators (LDOs) are straightforward to implement and have a very stable output with low voltage ripple. However, the efficiency of an LDO can fluctuate greatly, as the power dissipation is a function of the device’s input and output. On the other hand, a switching regulator uses a switch to regulate energy levels. These types of regulators are more versatile when a larger change of voltage is needed, as efficiency is relatively stable across larger steps of voltages. However, switching regulators tend to have a larger output voltage ripple, which can be an issue for sensitive systems. An approach to utilize both in cascaded configuration while providing a negative output voltage will be presented in this paper. The proposed two-stage conversion system consists of a switching pre-regulator that can track the negative output voltage of the second stage (LDO) such that the difference between input and output voltages is always kept small under varying output voltage while maintaining the high overall conversion efficiency. Computer simulation and hardware results demonstrate that the proposed system can track the negative output voltage well. Additionally, the results show that the proposed system can provide and maintain good overall efficiency, load regulation, and output voltage ripple across a wide range of outputs.
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Andersson, Anton, and Dexter Wolffsohn. "Regulatory Focus and Penalty Taking in Handball." Thesis, Högskolan i Halmstad, Hälsa och idrott, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-41613.
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Penalty-taking performance in handball within a self-regulatory focus framework was examined. In a two-independent group design, regulatory framings (either promotion or prevention) were given to participants (N = 25) prior to penalty-taking. More precisely, Swedish male (n = 15) and female (n = 10) players of the third male and second female Swedish Leagues were randomly allocated to shoot three penalties each under either a promotion-framed (n = 13; Mage = 20.77, SD = 3.77 years) or a prevention-framed (n = 12; Mage = 19.25, SD = 2.09 years) condition. Positive and negative affect were measured to assess pre-performance emotional states. Findings showed that promotion–focused individuals performed better in a promotion– framed penalty (i.e. fit) than in a prevention–framed (i.e. mismatch). Moreover, when in regulatory fit, pre-performance positive emotions were reported to be greater than when in mismatch. Findings are discussed in terms of role of fit and emotional states in pressureperformance critical situations.Straffläggnings prestation i handboll inom ett själv-regulatoriskt fokus-ramverk undersöktes. I en två-oberoende grupps design, regulatorisk inramning (antingen promotion eller prevention) gavs till deltagarna (N = 25) innan straffläggning. Mer exakt, svenska manliga (n = 15) och kvinnliga (n = 10) spelare från den manliga tredje och kvinnliga andra svenska divisionen var slumpmässigt tilldelade att skjuta tre straffar under antingen en promotion-inramad (n = 13; Målder = 20.77, SD = 3.77 år) eller prevention-inramad (n = 12; Målder = 19.25, SD = 2.09 år) straffsituation. Mätningar av positiva och negativa affekter bedömde pre-prestation emotionella tillstånd. Resultaten visade att promotions-fokuserade individer presterade bättre i en promotion-inramning straffsituation (fit) än i en prevention-inramning straffsituation (mismatch). Dessutom när i regulatoriskt-fit, rapporterades positiva emotioner högre än i mismatch. Resultaten är diskuterade i förhållande till rollen av fit och emotionella tillstånd i prestation-under-press kritiska situationer
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Giesen, Kay. "Die tramtrack-Gengruppe - negative Regulatoren zellulärer Differenzierung?" [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=95981227X.
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Farrah, Jennifer. "CEACAMI as a negative regulator of T cell functions." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=81247.
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CEA-related cell adhesion molecule 1 (CEACAM1) is a member of the carcinoembryonic antigen (CEA) family that is expressed on activated T lymphocytes. Previous studies have reported both costimulatory and coinhibitory roles for this glycoprotein in T cell activation and effector functions. We have used a Ceacam1-/- mouse model to further explore this paradox. We demonstrate that CEACAM1 is not involved in T cell development or in migration of these lymphocytes to peripheral lymphoid organs. In vitro, CEACAM1 was observed to play an inhibitory role on T lymphocytes as it limits T cell proliferation in response to T cell receptor-specific antibodies and mitogens. In vivo proliferative responses were not affected by the absence of CEACAM1 upon administration of antigen emulsified with adjuvant, yet cytokine secretion revealed that CEACAM1 may be involved in the control of Th1-type responses. A new transgenic model for CEACAM1 overexpression on T lymphocytes was generated and further experimentation will be necessary to confirm the above observations. Hence, CEACAM1 is playing an inhibitory role on T cell surfaces, most likely by intracellular signal transmission through its ITIM motifs.
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Doughty, Phillip Andrew. "Protein engineering of the ferric uptake regulator from Pseudomonas aeruginosa." Thesis, University of East Anglia, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390637.
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Li, Grace T. Y. "C/EBPbeta is a Negative Regulator of Skeletal Muscle Differentiation." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20110.
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C/EBPβ is a bZIP transcription factor known to be involved in various physiological processes, including adipogenesis, osteogenesis and liver development. Previous studies in this laboratory revealed an inhibition of myogenesis and reduced myogenic protein expression in 5-azacytidine treated mesenchymal stem cells retrovirally transduced to overexpress C/EBPβ. The goal of this thesis was to evaluate the role of C/EBPβ in myogenic differentiation by overexpression in C2C12 myoblasts and primary myoblasts. We demonstrate reduced MyoD protein expression and subsequent downregulation of myogenic proteins during differentiation following C/EBPβ overexpression. We localized C/EBPβ to the quiescent Pax7+ satellite cells associated with the muscle fiber. Upon satellite cell activation, we observed the downregulation of C/EBPβ protein expression prior to MyoD protein expression. Furthermore, the re-expression of C/EBPβ correlated with the loss of MyoD expression later in differentiation. Histological analysis of C/EBPβ-/- mice revealed smaller fibers and a reduced Pax7+ satellite cell population as compared to control animals. In this thesis, we propose that C/EBPβ is a negative regulator of skeletal muscle differentiation by inhibiting the expression of MyoD, thus impairing proper progression through the myogenic program. In addition, we propose a role for C/EBPβ in the maintenance of undifferentiatied satellite cells.
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Gour, Naina. "Dectin-1 is a critical negative regulator of allergic asthma." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1413472037.
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Pradhan, Madhura. "Ship : a negative regulator of RAS Pathway in B Lymphocytes /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488194825666984.
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Sturrock, Marc. "Spatio-temporal modelling of gene regulatory networks containing negative feedback loops." Thesis, University of Dundee, 2013. https://discovery.dundee.ac.uk/en/studentTheses/b824506e-d515-442a-b9dc-ff82568f3c09.
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Stephenson, Natalie. "Mechanotransduction of the Notch signalling pathway via the negative regulatory region." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/mechanotransduction-of-the-notch-signalling-pathway-via-the-negative-regulatory-region(c13c0f01-3095-4895-a536-1dfc324d9899).html.
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The Notch receptor is part of a highly conserved omnipresent developmental pathway that has crucial roles in developing and self-renewing tissues. During activation of the signalling pathway Notch binds to its ligand, presented on a neighbouring cell. It is thought that this results in a conformational change within the Negative Regulatory Region (NRR) unmasking a key proteolytic site (S2) and allows for metalloprotease cleavage. This facilitates further cleavage by gamma-secretase, initiating downstream events. Thus far, the molecular mechanism by which the S2 site is revealed has not been defined, though indirect evidence favours a model whereby transendocytosis of the Notch extracellular domain into the ligand bearing cell results in mechanical unfolding of the NRR. Research presented here suggests the NRR of human Notch2 (hN2) unfolds within a mechanosensing force range. Furthermore, through the application of a force (200 pN) the hN2-NRR was shown to unfold sufficiently to expose the S2 site allowing cleavage by metalloproteases. Molecular dynamics (MD) simulations offer insight into the unfolding process of the hN2-NRR, revealing near-sequential unfolding of its constituent LNR and HD domains. Removing the linker region between LNR’s A and B appears to be the first force ‘barrier’ in the unfolding pathway, producing the largest increase in solvent accessibility at the S2 cleavage site. Through docking simulations, this unfolding event was shown to expose the S2 cleavage site sufficiently to allow access to the metalloprotease TACE. Removing coordinated metal ions from the hN2-NRR structure resulted in a dramatic decrease in the forces required for unfolding during AFM experiments, highlighting their role in increasing the resistance of the hN2-NRR to forced unfolding. Removal of disulphide bonds within the structure resulted in a loss of detectable LNR unfolding, highlighting their role in LNR stabilisation.Six HD destabilising mutants, characterised through their role in the hN1 disease, T-cell Acute Lymphoblastic Leukemia, showed three key changes to the unfolding pathway of the hN2-NRR. Firstly, mutants A1647P, L1573P and V1623D showed a dramatic decrease in force required for unfolding in AFM experiments. MD simulations highlighted a lack of force required for the unfolding the LNRA:B linker previously characterised as the key event in removing NRR autoinhibition. Secondly, all the mutants studied here showed changes to the stability of the alpha3-helix (within the HD domain) resulting in transient shifts or bending during unfolding of the LNRA:B linker and the LNRB. Finally, changes were observed within the LNRC of A1647P and L1566P. Within these mutants the LNRC was observed to be unfolding, an event not present during wild-type unfolding. Within mutant L1566P this is thought to be due to the disruption of the conserved salt-bridge occurring between Arg1567 (HD domain) and Asp1506 (LNRC). Within mutant A1647P this is likely due to widespread domain destabilisation. Overall, research presented here has provided the first direct evidence that the NRR is mechanosensing and that mechanical force can allow for cleavage at the S2 site. Further characterisation has been performed to analyse the unfolding pathway through ion chelation, disulphide oxidation and mutagenesis studies.
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Liu, Jinqi. "Characterization of negative regulatory proteins involved in tissue specific MMTV expression /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Song, Xiaozheng. "Estrogen Receptor Beta Is A Negative Regulator Of Mammary Cell Proliferation." ScholarWorks @ UVM, 2014. http://scholarworks.uvm.edu/graddis/259.
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The mammary gland cell growth and differentiation are under the control of both systemic hormones and locally produced growth factors. Among all these important hormones and growth factors, estrogen plays a central role in mammary gland development. The biological function of estrogen is mediated by estrogen receptor α (ERα) and estrogen receptor β (ERβ). Both ERα and ERβ are expressed in the mammary gland, but with distinct expression patterns. In the mammary gland, ERα has been proved to be the estrogen receptor that mediates the mitogenic function of estrogen. However the function of ERβ in mammary cell proliferation is less understood and there remains some controversy. Accumulating evidence indicates that ERβ, unlike ERα, is a negative regulator of mammary epithelial cell proliferation.
In this dissertation, ERα and ERβ were evaluated for their expression patterns in the mammary gland. In the proestrus phase, ERα was detected in about 20% of mammary epithelial cells; in the diestrus phase, no ERα staining was detected in the mammary gland. ERβ was expressed in more than 50% of mammary epithelial cells and ERβ staining was detected in some stromal cells in the proestrus phase. In the diestrus phase, ERβ staining cells were very limited and the staining intensity was very weak. These data suggest that the expression levels of both ERα and ERβ undergo dynamic changes during the estrous cycle. In the ovariectomised (OVX) rats, both ERα and ERβ were detected in more than 50% of mammary epithelial cells. Compared with the ovary-intact rats, the mammary gland of the OVX rats showed more cells with ERα expression, but the staining intensity was weaker. Taken together, the expression of ERα and ERβ is regulated by estrogen in normal mammary gland, while without estrogen stimulation in the OVX rats, more mammary cells showed ERα expression, but at a lower level in these cells.
The effects of ERα and ERβ on mammary cell proliferation were studied by two different approaches, activation of endogenous ERα and ERβ via selective agonists, and overexpression of ERα and ERβ via lentiviral infection. In the first approach, we used ERα and ERβ selective agonists, propylpyrazole-triol (PPT) and diarylpropionitrile (DPN) respectively, to activate endogenous ERα and ERβ in the OVX rats. We found that ERβ selective agonist DPN counteracts the proliferative effect of ERα selective agonist PPT in the mammary gland. In the second approach, ERα and ERβ were ectopically overexpressed in the mammary gland of mature virgin rats by lentivirus infection. We found that ERβ overexpression significantly decreased mammary cell proliferation rate in both the proestrus and diestrus phases, indicating that ERβ, unlike ERα, is a negative regulator for mammary cell proliferation. Collectively, these data supports that in contrast to ERα, ERβ activation or overexpression is able to inhibit mammary cell proliferation.
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Wee, Hee-Jun. "Serine phosphorylation of RUNX2 with novel potential functions as negative regulatory mechanisms." Kyoto University, 2003. http://hdl.handle.net/2433/149370.
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Centuori, Sara Mozelle. "NEGATIVE REGULATION OF REGULATORY T CELLS BY MYELOID-DERIVED SUPPRESSOR CELLS IN CANCER." Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/145099.
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Myeloid-derived suppressor cells (MDSC) and regulatory T cells (Treg) play an essential role in the immunosuppressive networks that contribute to tumor immune evasion. The mechanisms by which tumors promote the expansion and/or function of these suppressive cells and the cross-regulation between MDSC and Treg remain incompletely defined. The current work evaluates the influence of MDSC, expanded in two mouse cancer models, on immunosuppressive Treg. We demonstrate that tumor-induced MDSC endowed with the potential of suppressing conventional T lymphocytes surprisingly impair TGF-β1-mediated generation of induced Treg (iTreg) from naïve CD4⁺ T lymphocytes. Suppression of iTreg generation by MDSC occurs early in the differentiation process, and is cell contact dependent. This inhibition of FoxP3-expressing T lymphocyte differentiation by MDSC does not depend on arginase 1, cystine/cysteine depletion, iNOS/NO, or PD-1/PD-L1 signaling. These findings therefore indicate that MDSC from tumor-bearing hosts have the heretofore unreported ability to restrict some immunosuppressive Treg subpopulations.
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Chan, James Yi-Hsin. "The isolation and characterisation of the CD164 gene, a negative regulator of haematopoiesis." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301889.
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Kingsbury, Joanne Maree. "Characterisation of a negative regulator of hydrophobic amino acid transport in Saccharomyces cerevisiae." Thesis, University of Canterbury. Plant and Microbial Sciences, 2000. http://hdl.handle.net/10092/5737.
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Yeast have many systems for nitrogen regulation. Combined, these systems make a complex network balancing uptake of nitrogenous compounds and their assimilation in diverse environments. Yeast preferentially use more easily assimilated nitrogen sources when they are available, and under these conditions, many permeases that transport less easily utilisable amino acids are inactive. This study characterises a spontaneous mutation that results in deregulation of an apparently unique hydrophobic amino acid permease (entitled Lup for Leucine uptake), in the presence of ammonium. The mutant, Lup+ phenotype (ability to grow in leucine limiting conditions), was recessive and postulated to be due to a mutation in a gene, designated LUP1, which encodes a represser of the Lup permease. Since Lup+ cells better accumulated hydrophobic amino acids, we used toxic amino acid analogs in growth media to select for LUP1 (or LUP/lup1) genotypes. Interestingly, we have observed that Lup+ variants were more sensitive than their progenitor to not only the expected hydrophobic amino acid analogs L-methionine sulfoximine, L-ethionine and m-fluoro-D,L-phenylalanine, but also the nonhydrophobic analogs L-canavanine and L-azaserine. A screen of two wildtype yeast genomic libraries has identified 14 plasmids that complement the m-fluoro-D,Lphenylalanine sensitive (Fpas) phenotype of the lup1 allele. Sequence data of complementing plasmids, extending outwards from transposons whose insertions defined the physical size of the complementing unit, has revealed that two genes, BUL1 and AR04, can complement the Fpas phenotype. BUL1, but not AR04, could also render Lup+ cells Lup- (unable to grow in limited leucine environments), thus was predicted to be allelic to LUP1. Several additional lines of evidence demonstrated that LUP1 and BUL1 were allelic: (i) partial deletion of chromosomally encoded BUL1resulted in Lup+ phenotypes; (ii) like bull mutants, lup1 mutants were temperature sensitive; (iii) LUP1 and BUL1 were in the same, or extremely close, chromosomal position; and (iv) Lup+ mutants had an altered BUL1 sequence to wildtype. The nature of changes to the BUL1 sequence occurring in two Lup+ variants consisted of point mutations occurring at different positions.
Bull is thought to be involved in the ubiquitination pathway due to physical interaction with the Rsp5 ubiquitin ligase. Rsp5 has been implicated directly with the ubiquitin-dependent internalization and down-regulation of at least four yeast plasma membrane proteins. Rsp5 may also be involved in regulation of the Lup permease as a mutation in Lup1/Bul1 that eliminates its ability to bind to Rsp5 also abolishes its capacity to complement the Lup+ and Fpas phenotypes. Based on these phenotypes, the following model was proposed: Lup1/Bul1 functions with Rsp5 as an E3 complex for the recognition and subsequent ubiquitination of the Lup permease, targeting this protein for destruction in the presence of ammonium.
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Chan, Sze-lai Celine, and 陳思例. "Sclerostin: a negative regulator of bone formation and a target for osteoporosis therapy." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B4189702X.
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Baggott, Rhiannon Rebecca. "Role of the plasma membrane calcium ATPase as a negative regulator of angiogenesis." Thesis, University of Wolverhampton, 2014. http://hdl.handle.net/2436/332139.
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Angiogenesis is the formation of new blood vessels from pre-existing ones. Unregulated angiogenesis is associated with several diseases such as diabetic retinopathy and tumour growth. Many signal transduction pathways have been implicated in the regulation of angiogenesis such as p38 mitogen-activated protein kinase (MAPK), phosphatidylinositol-3 kinase (PI3K), extracellular signal-related kinase 1/2 (Erk1/2) and of particular interest the calcineurin/nuclear factor of activated T-cell (NFAT) pathway. Inhibition of calcineurin activity by the drug cyclopsorin A (CsA) has been shown to inhibit processes required for successful angiogenesis such as in vitro cell migration, tube formation and additionally attenuates corneal angiogenesis in vivo. CsA is associated with severe side effects and therefore the identification of an endogenous regulator of this pathway would be beneficial. One possibility is the plasma membrane calcium ATPases (PMCAs). These high affinity calcium extrusion pumps have been shown to interact with calcineurin in mammalian cells and cardiomyocytes and down-regulate the calcineurin/NFAT pathway. This is hypothesised to be due to the interaction between the two proteins which maintains calcineurin in a low calcium micro-environment generated by the calcium removal function of the pump. Interestingly, PMCA4 has been shown to interact with calcineurin in endothelial cells. The aim of our study was to further our understanding of PMCA4s regulation of the calcineurin/NFAT pathway specifically in endothelial cells and establish if PMCA4 has a role in the regulation of angiogenesis. ‘Gain of function’ by adenoviral over-expression of PMCA4 and ‘loss of function’ by either si-RNA mediated knockdown of PMCA4 or isolation of PMCA4-/- MLEC were used as models. Over-expression of PMCA4 in HUVEC resulted in inhibition of the calcineurin/NFAT pathway with the opposite result occurring in the case of the knockout of PMCA4, identifying PMCA4 as a negative-regulator of the calcineurin/NFAT pathway in endothelial cells. Over-expression of PMCA4 significantly attenuated VEGF-induced protein and mRNA expression of the pro-angiogenic proteins RCAN1.4 and Cox-2, endothelial cell migration and in vitro and in vivo tube formation with the opposite result occurring in knockdown or knockout studies, confirming PMCA4 as a down-regulator of angiogenesis. Interestingly, over-expression or knockdown of PMCA4 had no effect on VEGF-induced HUVEC proliferation or Erk1/2 phopshorylation proposing PMCA4 may be a potential inhibitor of angiogenesis without compromising cell survival. Disruption of the interaction between PMCA4 and calcineurin by generation and ectopic expression of an adenovirus encoding the region of PMCA4 that interacts with calcineurin (428-651) (Ad-ID4) resulted in an increase in NFAT activity, RCAN1.4 protein expression and in vitro tube formation. These results identify the mechanism of PMCA4s inhibitory effect of the calcineurin/NFAT pathway and consequently angiogenesis is a result of the interaction between the two proteins. The novel findings of this study establish PMCA4 as a negative-regulator of the calcineurin/NFAT pathway in endothelial cells and angiogenesis. These results are far reaching and highlight a potential role for PMCA4 as a therapeutic target in a variety of diseases that are associated with pathological angiogenesis.
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Jung, Joo-Yong. "INTERLEUKIN-10 AS A NEGATIVE REGULATOR OF INTERFERON-MEDIATED IMMUNITY IN CHLAMYDIAL INFECTIONS." Miami University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=miami1196971379.
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Mitton, Bryan A. "Protein Phosphatase Inhibitor-1 as a Positive Or Negative Regulator of Cardiac Contractility." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1195325467.
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Chan, Sze-lai Celine. "Sclerostin a negative regulator of bone formation and a target for osteoporosis therapy /." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B4189702X.
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Tews, Martha [Verfasser]. "Cholesterol als negativer post-transkriptioneller Regulator der Selenoprotein-Expression / Martha Tews." Mainz : Universitätsbibliothek Mainz, 2019. http://d-nb.info/1194189547/34.
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Wilson, Maria Elizabeth. "Characterisation of hormone responsive and negative regulatory elements in the human insulin gene enhancer." Thesis, University of Aberdeen, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295586.
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A hormone response element and a negative regulatory element upstream of the human insulin gene have been investigated. The hormone response element is located one kilobase upstream of the transcription start site. When isolated and placed upstream of a viral promoter, it has been found to increase transcription in response to retinoic acid and thyroid hormone. It is also able to mediate a transcriptional response to retinoic acid, and to the retinoic acid receptor in the context of the entire insulin gene promoter/enhancer region. This element is able to bind to members of the retinoid receptor family in vitro. Insulin gene transcription in isolated human islets of Langerhans was also shown to be upregulated by retinoic acid. The negative regulatory element within the human insulin gene enhancer lies between 279 and 258 base pairs upstream of the transcription start site, although it relies upon nearby insulin enhancer sequence in order to act upon a heterologous promoter. The transcriptional silencing properties of the negative element can be abolished by point mutations of critical residues. The element forms several complexes with nuclear proteins from an insulin producing cell line, one of which is related to the ubiquitous POU domain factor, Oct-1. The relevance of these findings to the control of insulin gene transcription is discussed.
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Belloc, Rocasalbas Eulàlia. "Identification of a new deadenylation negative feedback loop that regulates meiotic progression." Doctoral thesis, Universitat Pompeu Fabra, 2008. http://hdl.handle.net/10803/7179.
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Els oòcits de vertebrats es troben aturats a la profase I de la primera meiosi (PI). Durant el procés anomenat oogènesi, els oòctits sintetitzen i emmagatzemen grans quantitats d'ARN missatgers(ARNm)que els seran necessaris per la compleció de la meiosi.I,per posteriorment, aturar-se de nou a la metafase de la segona divisió meiòtica (MII) per l'activitat del factor citostàtic(CSF).D'aquestes divisions en destaca el fet que transcorren en absència de transcripció, i per tant depenen totalment en l'activació traduccional dels ARNm anteriorment esmentats que han estat acumulats durant l'oogènesi. L'activació traduccional d'aquests missatgers és principalment induïda per l'elongació de les cues d'adenines(cues de poli(A)), aquest procés és mediat per les seqüències de poliadenilació citoplasmàtiques (CPE)presents a la regió 3' no tradudïda (3'UTR)dels ARNm. El moment i la longitud de la poliadenilació dels ARNm que contenen CPEs estan finament regulats, de manera que en combinació amb la degradació de proteïnes, s'estableixen els patrons específics d'expresió de les proteïnes que condueixen la meiosi (Shmitt et al., 2002; de Moor and Richter, 1997; Ballantyne et al., 1997; Mendez et al., 2002; Charlesworth et al., 2002). Fins a la data, no s'havia descrit que la deadenilació (escurçament de la cua de poli(A)) fos necessària per la progressió meiòtica. En aquesta tesi s'ha descrit, a partir d'un cribatge d'abast genòmic, una ruta de retroalimentació negativa requerida per a la sortida de la primera metafase meiòtica. La nova ruta identificada, a més té la particularitat d'actuar a nivell traduccional regulant l'expressió de proteïnes que participen directament en la progressió meiòtica. L'element central d'aquesta nova ruta és la proteïna C3H-4, que a la vegada és regulada per poliadenilació citoplasmàtica. C3H-4 crea la retroalimentació negativa interaccionant amb elements ARE de les regions 3'UTR, promovent la deadenilació del ARNm al qual s'uneix. D'entre les seves dianes hem identificat Emi1 i Emi2, ambdós reguladors de l'activitat de l'APC/C, crítica per la divisió cel·lular.
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Campbell, Charles. "Sortilin is a Negative Regulator of Sonic Hedgehog Processing and Anterograde Trafficking in Neurons." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34560.
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Sonic Hedgehog (SHH) is a secreted morphogen that is an essential regulator of patterning and growth. The SHH protein requires cleavage of its full-length precursor (SHHFL) for secretion of biologically active SHH (SHHNp). Mutations in SHH that affect SHH processing are associated with human disease, which highlights the importance of processing for patterning in vivo. We identified Sortilin (SORT1), a member of the VPS10P receptor family, as a novel SHH interacting protein. SORT1 preferentially associates with SHHFL and SORT1 levels correlate inversely with cleavage of SHHFL. Consistent with an antagonistic relationship between SORT1 and SHH processing, loss of SORT1 results in an increase in SHH levels in axons and a partial rescue of Hedgehog-associated patterning defects in a mouse model of deficient SHH processing. Finally, we demonstrate a functional requirement for SORT1-mediated trafficking on SHH-dependent signaling from axons in the developing visual system in vivo. Our findings identify a novel role for SORT1 in the regulation of SHH processing and trafficking.
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Baril, Caroline. "The PP2C phosphatase Alphabet is a general negative regulator of MAPK signaling in Drosophila." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18415.
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The Mitogen-Activated Protein Kinase (MAPK) pathways are evolutionarily conserved signaling units implicated in the transmission of extracellular cues to intracellular compartments. The ERK, JNK and p38 pathways are the best described MAPK cascades. Their function relies on a core module of three kinases, composed of a MAPK Kinase Kinase (MAPKKK), a MAPK Kinase (MAPKK) and a MAPK, which becomes sequentially phosphorylated upon mitogenic, proinflammatory or stress signals. These modules are used in various developmental contexts and are implicated in the maintenance of homeostasis in adult organisms. Although most of the core components of MAPK signaling pathways have been discovered, the molecular mechanisms that control signaling strength, duration, location and termination remain poorly characterized. Using a genetic screening approach in Drosophila, our research group has identified several new loci potentially implicated in the regulation of ERK/MAPK signaling. Therefore, my doctoral research has focused on the characterization of one of these loci, that we renamed alphabet (alph). The alph locus encodes a functional Ser/Thr phosphatase, which is highly homologous to mammalian PP2Ca/ß. In a first set of experiments, I demonstrated that Alph phosphatase activity was required for the negative regulation of ERK/MAPK signaling at a step downstream of the small GTPase Ras and possibly upstream of ERK/MAPK during Drosophila development. In yeasts, plants and mammals, PP2C phosphatases are implicated in the downregulation of JNK and p38 Stress-Activated Protein Kinase (SAPK) pathways. Accordingly, I showed that Alph activity was also implicated in the inhibition of SAPK signaling at a step upstream of the MAPKKs Hemipterous and Licorne and potentially downstream of the small GTPase Rac1. In addition, biochemical evidence suggests that MAPKKKs such as Slipper/MLK, dDLK and Tak1 are candidate substrates for Alph. Finally, transcriptional profiling in alph mutant flieLes voies de signalisation de type MAPK ont été hautement conservées au cours de l'évolution et sont principalement impliquées dans la transmission de signaux extracellulaires vers les compartiments intracellulaires. Les voies ERK, JNK et p38 sont les cascades de type MAPK les mieux décrites et reposent sur l'activation d'un module de trois kinases par phosphorylation séquentielle. En effet, lorsqu'un signal mitogénique, proinflammatoire ou de stress est perçu par la cellule, une MAPK Kinase Kinase (MAPKKK) phosphorylera une MAPK kinase (MAPKK) qui phosphorylera ensuite une MAPK. Ces modules sont utilisés dans une multitude de contextes développementaux ainsi que pour le maintien de l'homéostasie chez les organismes adultes. Bien que la majorité des constituants de base des modules MAPK soient connus, nous possédons peu d'information concernant les mécanismes moléculaires impliqués dans le contrôle de la force, la durée, la localisation et la terminaison du signal. Par le biais de cribles génétiques chez la Drosophile, notre équipe a identifié plusieurs nouveaux loci potentiellement impliqués dans la régulation de la voie de signalisation ERK/MAPK. Par conséquent, l'objectif principal de mes recherches doctorales a porté sur la caractérisation d'un de ces nouveaux loci, que nous avons renommé alphabet (alph). Le gene alph encode une Ser/Thr phosphatase ayant une forte homologie de séquence avec PP2Ca/ß de mammifère. Dans un premier temps, j'ai démontré que l'activité phosphatase d'Alph était requise pour l'inhibition de la voie ERK/MAPK en aval de Ras et possiblement en amont de ERK/MAPK. Chez les levures, les plantes et les mammifères, les phosphatases de type PP2C sont principalement impliquées dans l'inactivation des voies JNK et p38. De façon similaire, j'ai démontré dans un deuxième temps qu'Alph agit aussi comme régulateur négatif de ces deux voies chez la Drosophile, possiblement en aval de Rac1 et en amont des M
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Chan, Wilson. "Studies on the molecular mechanisms of Fibulin-5 as a negative Regulator of Angiogenesis." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=96718.
Full textAbstract:
Angiogenesis is a tightly regulated process by which new blood vessels are formed from pre-existing blood vessels. It is a complex process modulated by a multitude of pro- and anti-angiogenic factors, some of which naturally include members of the extracellular matrix (ECM) due to the high degree of tissue remodeling necessary in angiogenesis. Fibulin-5 (DANCE, EVEC) is an integrin- and elastin-binding ECM protein that is highly expressed in blood vessels during development, is up-regulated upon vascular injury and is involved in the regulation of the transition of vascular SMCs from a quiescent to proliferative state. Recently, Fbln5-/- mice have been shown to have an increase in cutaneous blood vessels, increased migration and proliferation of endothelial cells (ECs) and a 30-fold increase in angiopoietin-1 (Ang-1) expression in vascular SMCs, which is a potent promoter of angiogenesis. In the present study, we sought to investigate the molecular mechanism(s) by which fibulin-5 might act as a negative regulator of angiogenesis, with a focus on the modulation of Ang-1 activity in ECs. We used solid-phase binding assays to determine the direct physical interactions that fibulin-5 might have with Ang-1 and its receptor Tie-2. We used solid-phase binding assays to determine the cell surface molecules that fibulin-5 might bind and confirmed an RGD dependency of fibulin-5 for integrin binding and showed a high affinity for heparin, suggesting a potential interaction with cell surface heparan-sulfate proteoglycans. We also sought to understand the downstream signaling mechanism of fibulin-5 and established a novel Akt-dependent pathway by which fibulin-5 can act as an anti-angiogenic molecule.L'angiogenèse est un processus finement régulé par lequel de nouveaux vaisseaux sanguins se forment dans les vaisseaux sanguins préexistants. Il s'agit d'un processus complexe modulé par une multitude de facteurs pro-et anti-angiogéniques, qui incluent naturellement les membres de la matrice extracellulaire (MEC) en raison du degré élevé de remodelage tissulaire nécessaire dans l'angiogenèse. La Fibulin-5 (DANCE, EVEC) est une protéine de la MEC liant les intégrines et l'élastine. Elle est fortement exprimée dans les vaisseaux sanguins au cours du développement, est régulée à la hausse lors de lésion vasculaire et est impliquée dans la régulation de la transition des cellules musculaires lisses (CML) vasculaires d'un état de repos à un état de prolifération. Récemment, les souris Fbln5 -/- ont montré une augmentation de vaisseaux sanguins cutanés, une augmentation de la migration et de la prolifération des cellules endothéliales (CEs) et une augmentation de 30 fois de l'expression de l'angiopoïétine-1 (Ang-1) dans les CML vasculaires, un promoteur puissant de l'angiogenèse. Dans la présente étude, nous avons étudié le(s) mécanisme(s) moléculaire(s), par le(s)quel(s) la fibuline-5 pourrait agir comme un régulateur négatif de l'angiogenèse, plus précisément, sur la modulation de l'activité Ang-1 dans les CEs. Nous avons utilisé des essais de liaison en phase solide afin de déterminer les interactions physiques directes que la fibuline-5 pourrait avoir avec l'Ang-1 et son récepteur Tie-2. Nous avons également utilisé des essais de liaison en phase solide pour enquêter sur les molécules de surface cellulaire pouvant lier la fibuline-5 et nous avons confirmé que le motif RGD de la fibuline-5 sert à la liaison aux intégrines. De plus, la fibuline-5 a une grande affinité pour l'héparine, suggérant une interaction potentielle avec la surface cellulaire par les protéoglycanes héparane-sulfate. Nous avons également cherché à comprendre le mécanisme de signalisation en aval de la fibuline-5 et nous avons établi une nouvelle voie dépendante d'Akt dans laquelle la fibuline-5 agit comme une molécule anti-angiogénique.
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McCrindle, Tyronne K. "Characterisation of the AT4G11100 gene, a negative regulator of disease resistance in Arabidopsis thaliana." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/15728.
Full textAbstract:
Plants have evolved a complex system of defence to prevent pathogen establishment. The Arabidopsis thaliana cir1 (constitutively induced resistance 1) mutant displays enhanced resistance to infection by the virulent bacterial pathogen Pseudomonas syringae and constitutively expresses a number of defence genes. Evidence suggests that CIR1 is a negative regulator of plant immunity important in the absence of pathogen attack. Genetic mapping experiments indicate that cir1 is located on the lower arm of chromosome 4 of A. thaliana and may be one of 8 known genes in the region. Analysis of T-DNA knockouts of these 8 genes suggests that AT4G11100 is the mostly likely candidate for CIR1. This project established that the disease resistance phenotype of cir1 is temperature dependent and linked to reduced plant growth. Genetic crosses between cir1 and at4g11100 T-DNA knockout mutants revealed that the mutants complement and therefore AT4G11100 is not CIR1. However, like cir1, the at4g11100 T-DNA knockout mutants display enhanced disease resistance. Over expression of AT4G11100 leads to increased susceptibility to infection by Pseudomonas syringae (Pst) and reduced induction of the salicylic acid defence gene PR2 following Pst infection, suggesting that AT4G11100 may too be a negative regulator of immunity. Additionally, a plant line with exceptionally high AT4G11100 expression levels displayed distinct leaf morphology, possibly implicating AT4G11100 in leaf development.
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Gomes, Nuno Miguel Araújo da Cunha. "NDT80 transcription factor as a negative regulator for Candida parapsilosis adhesion and biofilm formation." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14925.
Full textAbstract:
Mestrado em Biologia Molecular e CelularC. parapsilosis infections incidence has been increasing for the past 20 years. Its caracteristics of adhering and forming biofilms are a critical factor for infection caused by this organism, affecting from immunocompromised or transplanted patients to low-birth-weight neonates. The health-care workers are a major transmission vehicle of this fungus. The azoles class of antifungal drugs are the first and most common line of defense to treat infections by this type of yeast species. Its mode of action on the yeast cell works by inhibiting the lanoststerol 14α-demethylase, an enzyme belonging to the ergosterol biosyntethic pathway.. On a recent study it has become clear that C. parapsilosis antifungal azole resistance may display similar resistance mechanisms that the ones described for C. albicans. A resistant strain obtained after exposure to posaconazole has shown an upregulation of two transcriptional factors, Upc2 and Ndt80. The aim of this work was to assess the role of these two transcriptional factors on C. parapsilosis azole resistance. For that, it was intended to knockout both genes using the SAT1-flipper cassette. The strain obtained after disruption of one copy of NDT80 gene displayed an unexpected phenotype, concerning adhesion and biofilm formation, comparatively to the wild-type BC014 strain. It were also made susceptibility tests although with no evident changes. These results demonstrate that NDT80 gene may be a negative regulator of C. parapsilosis adherence to abiotic and biotic substrates, impairing also biofilm formation.
As infecções por C. parapsilosis têm vindo a aumentar nos últimos 20 anos. As suas características intrínsecas de adesão e capacidade de formação de biofilmes são um factor critíco de infecção, sendo os pacientes transplantados ou com o sistema imunitário comprometido ou mesmo os neonatos de baixo peso o grupo de risco mais afectado. Os prestadores de cuidados de saúde são o meio de transmissão mais comum para a infecção por esta levedura. A classe dos antifúngicos azóis são a primeira linha de defesa para tratamento de infecções por este tipo de leveduras. Estes actuam inibindo a enzima lanosterol 14α-demethylase, enzima constituinte da via biossintética do ergosterol. Um estudo recente demonstrontrou que a resistência aos azoles em C. parapsilosis poderá ter os mesmos mecanismos observados e estudados em C. albicans. Uma estirpe resistente obtida após exposição a Posaconazole revelou uma sobre-expressão de 13 genes envolvidos na biossíntese do ergosterol, entre eles dois factores de transcrição, Upc2 e Ndt80. Com vista a avaliar o papel destes factores de transcrição na resistência aos azoles em C. parapsilosis, pretendeu-se efectuar a delecção dos dois genes usando a ferramenta molecular SAT1-flipper cassette. Apenas um alelo do gene NDT80 foi deletado, originando um fenótipo distinto em comparação com a estirpe original BC014, em particular na sua capacidade de adesão e de formação de biofilmes. Foram realizados testes de susceptibilidade embora sem qualquer diferença evidente entre fenótipos. Estes resultados demonstram que o gene NDT80 pode ser um regulador negativo da capacidade de adesão de C. parapsilosis, afectando também o seu potencial de formação de biofilmes.