Theses (M.S.)--Marshall University, 2006. / Title from document title page. Includes abstract. Includes vitae. Document formatted into pages: contains viii, 143 p. Bibliography: p. 52-58.

Thesis (Ph. D.)--University of Virginia, 2006. / Includes bibliographical references. Also available online through Digital Dissertations.

Th.--Sci. phys.--Paris 11--Orsay, 1983. N°: 2684. / Rés. en fr. et en angl.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Dissertation (Ph.D.).--University of Texas Graduate School of Biomedical Sciences at San Antonio, 2008. / Vita. Includes bibliographical references.

No description available.

As proteínas fosfatases desempenham um papel fundamental na modificação pós-traducional reversível de proteínas por fosforilação, ao atuarem na remoção do grupo fosforil estável de resíduos de serina, treonina e tirosina. Embora predominem em eucariotos, as serina/treonina fosfatases (STPs) também existem em bactérias, nas quais atuam controlando diversos aspectos fisiológicos e de virulência. Neste trabalho investigamos o papel das STPs na virulência e fisiologia de Chromobacterium violaceum, uma ?-proteobactéria que atua como um patógeno ocasional de humanos e é amplamente encontrada em água e solos de regiões tropicais e subtropicais. Análises in silico revelaram a presença de quatro STPs no genoma de C. violaceum, sendo que duas possuem apenas o domínio de fosfatase (CV_0881 e CV_3848) e duas possuem um domínio adicional de regulador de resposta (CV_2644 e CV_3505). Mutantes nulos foram construídos para as quatro STPs e todas estas linhagens apresentaram crescimento semelhante ao da linhagem selvagem em meio rico e meio mínimo. As linhagens mutantes ?0881, ?2644 e ?3505 não apresentaram alteração de virulência em camundongos. Os mutantes ?2644 e ?3505 apresentaram menor formação de biofilme, o que sugere papel dessas fosfatases neste processo. Uma caracterização mais aprofundada da linhagem ?3848 por diferentes técnicas de microscopia revelou que este mutante apresenta células de tamanho diminuído, irregularidades no envelope celular e problemas na distribuição do DNA. Estes dados sugerem que CV_3848 tem papel em divisão celular, condensação do material genético e manutenção da parede celular. Nos ensaios de virulência o mutante ?3848 mostrou menor capacidade de causar morte e manter-se no fígado de camundongos, indicando que a STP CV_3848 é importante na patogenicidade de C. violaceum. / Protein phosphatases play a key role in reversible post-translational modification of proteins through phosphorylation since they act removing the stable phosphoryl group of serine, threonine and tyrosine residues. Although dominant in eukaryotes, the serine/threonine phosphatases (STPs) also exist in bacteria, in which they act by controlling various physiological and virulence traits. In this work we investigated the role of STPs on the virulence and physiology of Chromobacterium violaceum, a ?-proteobacterium that occasionally acts as a pathogen of humans and it is widely found in water and soil of tropical and subtropical regions. In silico analyzes revealed the presence of four STPs in the genome of C. violaceum, two of which have only the phosphatase domain (CV_0881 and CV_3848) and two that possess an additional domain of response regulator (CV_2644 and CV_3505). Null mutants were constructed for the four STPs and all of them showed similar growth to the wild type strain on rich and minimal medium. The mutant strains ?0881, ?2644 and ?3505 did not show any change in virulence in mice. The ?2644 and ?3505 mutants had lower biofilm formation, suggesting the role of these phosphatases in this process. Further characterization of ?3848 by different microscopy techniques revealed that this mutant presents cells of diminished size, irregularities in the cellular envelope and problem on the DNA distribution. These data suggest that CV_3848 has role in cell division, condensation of the genetic material and cell wall maintenance. In virulence assays the ?3848 mutant showed a lower ability to cause death and to remain in the liver of mice, indicating that the STP CV_3848 is important for the pathogenicity of C. violaceum.

Growth suppression mediated by connexin 37 (Cx37; also known as GJA4) requires interaction between its C-terminus and functional pore-forming domain. Using rat insulinoma cells, we show that Cx37 induces cell death and cell cycle arrest, and slowed cell cycling. Whether differential phosphorylation might regulate intramolecular interactions, and consequently the growth-suppressive phenotype, is unknown. Protein kinase C inhibition increased the open state probability of low-conductance gap junction channels (GJChs) and reduced GJCh closed state probability. Substituting alanine at serine residues 275, 302 and 328 eliminated Cx37-induced cell death, supported proliferation and reduced the GJCh closed state probability. With additional alanine for serine substitutions at residues 285, 319, 321 and 325, Cx37-induced cell death was eliminated and the growth arrest period prolonged, and GJCh closed state probability was restored. With aspartate substitution at these seven sites, apoptosis was induced and the open state probability of large conductance GJChs (and hemichannels) was increased. These data suggest that differential phosphorylation of the C-terminus regulates channel conformation and, thereby, cell cycle progression and cell survival.

No description available.

Les bactéries phytopathogènes produisent des effecteurs de type III qui sont des facteurs de virulence injectés dans la cellule hôte afin de moduler les défenses et ainsi favoriser l'infection. L'effecteur PopP2 de Ralstonia solanacearum possède une activité acétyl-transférase qui est perçue par la paire de protéines de résistance RRS1-R et RPS4 dans le noyau des cellules végétales. Cette étape de perception conduit à l'activation des réponses de défenses. GTE9 et GTE11, deux protéines à bromodomaine d'Arabidopsis thaliana, s'apparentent à des lecteurs épigénétiques ciblés par PopP2. Nos données démontrent que ces protéines GTEs (i) interagissent avec PopP2 dans le noyau des cellules végétales et (ii) sont acétylées en présence de l'effecteur. De plus, GTE9 et GTE11 se lient in vivo et in vitro à des histones H4, suggérant que PopP2 interfère avec des processus de remodelage de la chromatine. / Microbial pathogens infect host cells by delivering virulence factors (effectors) that interfere with defenses, thereby favouring infection. The Ralstonia solanacearum PopP2 effector displays an acetyltransferase activity perceived by the Arabidopsis immune receptor pair, RRS1-R with RPS4, in the plant nucleus. This recognition step leads to the activation of immunity. Two Arabidopsis bromodomain-containing proteins , called General Transcription factor with Extra-terminal domain 9 and 11 (GTE9 and GTE11), were identified as PopP2-interacting partners. GTE9 and GTE11 are considered as epigenetic readers. Our data demonstrate that these GTEs proteins (i) interact with PopP2 in the plant nucleus and (ii) are acetylated in presence of the effector. Moreover, bromodomains of GTE9 and GTE11 bind in vivo and in vitro to Histone H4. Together, these data suggest that PopP2, through the targeting of GTE9 and GTE11, likely interfere with chromatin remodeling processes to affect ETS and/or ETI-related processes.