No description available.

No description available.

No description available.

<p> FKBP65 is a 65 kDa FK-506 binding protein containing 4 putative peptidyl prolyl isomerase (PPiase) domains, whose expression level parallels that oftropoelastin, the soluble precursor ofelastin. Studies from other laboratories have established that FKBP65 associates with tropoelastin (TE) in the endoplasmic reticulum (ER) and dissociates from TE before reaching the Golgi apparatus (Patterson et al., 2000). TE contains 12% proline residues, which are often found in VPGVG repeats, and it has been suggested that these repeats formp-turns and subsequently P-spirals (Urry et al., 1992). The formation ofthe P-spiral is thought to be essential to endow the elastic properties of the elastin fibers. In order to form a P-turn, the proline residue at position 2 ofthe VPGVG sequence must be in trans conformation (Urry et al., 1995). Therefore, it was hypothesized by Davis and coworkers (Davis et al., 1998) that FKBP65, as a PPiase, may play an important role in the folding oftropoelastin by enhancing the formation ofP-turns in the ER, and thus elastic fiber formation. In the present study we have studied the coacervation (a reversible, temperature-dependent, self association process) ofTE and recombinant elastin model polypeptide, EP4, in the absence or presence ofrecombinant FKBP65 (rFKBP65). rFKBP65 was shown to enhance the coacervation process of TE, by lowering the coacervation temperature (T c) and increasing the overall extent of coacervation. In the kinetic study ofcoacervation ofTE at a constant temperature, rFKBP65 increased both the initial rate ofthe coacervation process and the overall extent ofcoacervation. These effects are specific to rFKBP65, as FKBP12 has no effect on the coacervation process. Rapamycin, an inhibitor ofthe PPiase activity ofFK-506 binding proteins, did not alter rFKBP65's effect on TE coacervation. </p> <p>In contrast to TE, rFKBP65 affected the coacervation process ofEP4 by increasing the T c, and by enhancing the dissociation of coacervates when temperature is decreased. Once again, these effects are specific to rFKBP65, as FKBP12 and BSA were shown to have no effect on the coacervation ofEP4. The effect of small pH changes on rFKBP65 was also investigated, and it was found that lowering the pH from 7.5 to 6.0 had no effect on rFKBP65's secondary structure or coacervation-altering activity. </p> <p> In summary, this study, along with an earlier study from this laboratory, has shown that FKBP65 affects the coacervation process ofTE. In addition, the coacervation pro·cess of an elastin model polypeptide, EP4, is also modulated by FKBP65. However, the mechanism ofthese effects remains unclear. Nevertheless, along with the data established by other laboratories, FKBP65 does appear to be a strong candidate as a molecular chaperone for tropoelastin, and may play an important role in the elastogenesis process. </p> / Thesis / Master of Science (MSc)

Type IV pili (T4P) systems are widely utilized among bacteria to power and direct surface motility. The production and secretion of a viscous polysaccharide to provide friction and resistance to the extended pilus structure is seen in several species of cyanobacteria including Nostoc punctiforme. The complex coregulation of polysaccharide secretion and T4P motor activity is not fully understood, although studies indicate a consistent relationship between functional motility and intact pathways of polysaccharide secretion and pilus extension in cyanobacteria. Using a combination of protein-protein interaction analysis, cytological studies, and comparative genomics this study proposes a theoretical mechanism for T4P motor influenced regulation of hormogonium polysaccharide secretion by a heat-shock protein (HSP) DnaK-type chaperone system in N. punctiforme. The results of this study indicate a tripartite HSP system consisting of DnaK1, DnaJ3, and coregulator GrpE is influenced by the activation of certain motor proteins in the T4P complex and are required for the production and secretion of hormogonium polysaccharide. Conservation of this system in Synechocystis sp. also implies a potential system that is conserved among all motile cyanobacteria for regulation of T4P.

<p>The Gram-negative bacteria Chlamydia trachomatis is a common sexually transmitted pathogen that can cause severe sequelae including cause pelvic inflammatory disease and sterility. This obligate intracellular pathogen effectively manipulates host cellular functions by secreting virulence factors across its membrane bound vacuole. Identifying these virulence components and how they help in establishing an environment conducive for bacterial growth is central to understanding chlamydial pathogenesis. This is experimentally challenging due to a lack of tools to perform molecular genetic studies. In the absence of genetic tools, we developed a yeast model system to identify and characterize chlamydial proteins involved in virulence mechanisms. In this study we describe the identification of twenty-eight proteins potentially involved in modulating host cellular functions and the secretion of virulence factors into the host. Since the delivery of virulence proteins by a type three secretion (T3S) system is a critical step for Chlamydia, we identified the proteins that interacted with the T3S apparatus by yeast two-hybrid analysis. We discovered several novel interactions between and determined that the C. trachomatis T3S apparatus displayed a similar architecture to that of other T3S systems. Furthermore with these approaches we identified networks of proteins that interacted with the secretion apparatus including a novel secretion chaperone protein. We characterized Ct260/Mcsc one of the putative secretion and demonstrated that it represents a novel class 1B secretion chaperone protein. Unlike other known chaperones, Mcsc directly interact with a conserved component of the T3S apparatus cytoplasmic domain, CdsQ. These finding represents a novel mechanism by which the secretion chaperone protein Ct260 may increase the secretion efficiency of its effector cargo and may reveal new facets of secretory cargo recognition by T3S systems.</p> / Dissertation

Le virus de l'hépatite B (HBV) infecte de manière chronique 240 millions de personnes dans le monde, et est la principale cause de carcinome hépatocellulaire. Actuellement, les traitements standards permettent une suppression virale à long terme, mais ne sont pas capables d'éliminer complètement le virus, en raison de la persistance de l'ADN circulaire et clos de façon covalente (ADNccc). Ce minichromosome viral réside dans le noyau des hépatocytes infectés, grâce à sa structure chromatinienne. En effet, lors de l'infection d'un hépatocyte, l'ADN viral partiellement double brin (ADN relâché circulaire (rc)) est libéré dans le noyau, où il est réparé et enveloppé par des protéines histones, afin de former une structure d'épisome chromatinisé. Les mécanismes conduisant à la formation ainsi qu'à la chromatinisation de l'ADNccc sont encore largement inconnus, et leur élucidation constituerait une première étape vers l'identification de nouvelles cibles thérapeutiques, susceptibles d'altérer la persistance de l'ADNccc. Dans ce but, nous avons étudié le rôle des facteurs hôtes de réparation de l'ADN, et des voies d'assemblage des nucléosomes, dans la formation de l'ADNccc, à des stades précoces (entre 30 minutes et 72 heures) de l'infection, dans des lignées cellulaires d'HepG2-NTCP, ainsi que dans des hépatocytes primaires humains. Nous nous sommes particulièrement concentrés sur la protéine chaperone d'histones, HIRA, qui est connue pour déposer le variant d'histone 3.3 (H3.3) sur l'ADN cellulaire d'une manière indépendante de la réplication et en association avec le remaniement des nucléosomes pendant la transcription et la réparation de l'ADN. Nous avons été capables de détecter l'ADNccc dans la fraction nucléaire des hépatocytes dès 30 minutes et 24 heures post-infection, par qPCR et Southern Blotting (SB), respectivement. L'extinction de HIRA par ARN interférent (siARN) avant l'inoculation du virus, a conduit à une forte diminution de l'accumulation de l'ADNccc (à la fois par qPCR et Southern Blot), qui était indépendante de la protéine HBx (en utilisant un virus HBx-défectueux). Les niveaux d'ADNrc sont restés stables, indiquant soit une éventuelle transition de l'ADNrc en ADNccc incomplète, ou retardée. L'analyse par immunoprécipitation de la chromatine a montré que HIRA était liée à l'ADNccc dès 30 minutes après infection, et que son recrutement était concomitant avec le dépôt de l'histone H3.3, ainsi que la liaison de la protéine de capside du HBV (HBc). Après 24 heures d'infection, une augmentation de la liaison de H3.3 et de l'ARN polymérase II sur l'ADNccc a été observée, en corrélation avec l'initiation de la transcription de l'ARN viral de 3.5 kb. Par des expériences de co-immunoprécipitation et de test de proximité entre protéines (PLA), nous avons montré que HIRA était capable d'interagir avec HBc dans des hépatocytes infectés et dans une lignée cellulaire HepaRG exprimant HBc de manière inductible. En conclusion, nos résultats suggèrent que la chromatinisation de l'ADN viral entrant est un événement très précoce, nécessitant l'histone chaperone HIRA. Bien que HBx ne soit pas requis pour ce processus, HBc pourrait jouer un rôle majeur, suggérant que l'interaction entre HIRA et HBc pourrait représenter une nouvelle cible thérapeutique à étudier / Hepatitis B virus (HBV) chronically infects 240 million people worldwide and is the major cause of hepatocellular carcinoma (HCC). Currently standard-of-care treatments can achieve longterm viral suppression, but are not able to completely eliminate the virus, due to the persistence of the covalently closed circular DNA (cccDNA). cccDNA, the viral minichromosome, resides in the nucleus of infected hepatocytes by virtue of its chromatin structure. Indeed, upon entry into hepatocytes, the partially double stranded viral DNA (relaxed circular (rc)DNA) is released into the nucleus, where it is repaired and wrapped by histones to form an episomal chromatinized structure. The mechanisms leading to cccDNA formation and chromatinization are still largely unknown and their elucidation would be a first step toward the identification of new therapeutic targets to impair cccDNA persistence. To this aim, we investigated the role of host factors belonging to DNA repair and nucleosome assembly pathways in cccDNA formation at early time points (i.e. between 30 minutes and 72 hours) post-infection in both HepG2-NTCP cell line and Primary Human Hepatocytes (PHH). We particularly focused on the histone chaperone Hira, which is known to deposit histone variant 3.3 (H3.3) onto cellular DNA in a replication-independent manner and in association to nucleosome reshuffling during transcription and DNA repair. We were able to detect cccDNA in the nuclear fraction of hepatocytes as early as 30 minutes and 24h post-infection, by qPCR and Southern Blotting (SB), respectively. Knock-down of Hira by RNA interference before virus inoculation led to a strong decrease in cccDNA accumulation (both in qPCR and SB) which was independent from HBx protein expression (using an HBx defective virus). rcDNA levels remained stable, indicating either a possible incomplete or delayed rcDNA to cccDNA transition. Chromatin Immunoprecipitation analysis showed that Hira was bound to cccDNA already at 2 hours post-infection and that its recruitment was concomitant with the deposition of histone H3.3 and the binding of HBV capsid protein (HBc). After 24 hours of infection, an increase of H3.3 and Pol2 binding on cccDNA was observed, correlating with the initiation of the transcription of the 3.5 kb RNA. By Co-Immunoprecipitation and Proximity Ligation Assay experiments, we showed that Hira was able to interact with HBc in infected hepatocytes and in a HepaRG cell line expressing HBc in an inducible manner. Altogether, our results suggest that chromatinization of incoming viral DNA is a very early event, requiring the histone chaperone Hira. While HBx is not required for this process, HBc could play a major role, suggesting that the interaction between Hira and HBc could represent a new therapeutic target to be investigated

Au sein du noyau, l'ADN est organise en chromatine dont l'unité de base est le nucléosome. La structure de la chromatine est très dynamique, ce qui est nécessaire pour la plupart des opérations qui se produisent dans l'ADN telles que la réplication, la transcription, la réparation et la recombinaison. Le nucléosome est constitué de deux dimères H2A/H2B et deux dimères H3/H4 associés avec 147 paires de bases d'ADN. La protéine Nap1 est un chaperon d'histone H2A/H2B impliquée dans l'assemblage et démontage des nucléosomes. Nap1 protège les interactions non spécifiques entre l'ADN chargé négativement et les dimères H2A/H2B chargés positivement, afin de permettre la formation de la structure ordonnée des nucléosomes. Lors de l'assemblage des nucléosomes, les dimères d'histones H3/H4 sont déposés en premier lieu, suivi par le dépôt de dimères H2A/H2B. Lors du démontage du nucléosome, les dimères H2A/H2B sont retirés avant le retrait des dimères H3/H4. La determination de la structure du complexe Nap1-H2A/H2B pourra permettre une meilleure compréhension du processus d'assemblage du nucléosome. Dans cette étude, nous voulons comprendre comment le chaperon Nap1 cible spécifiquement les dimères d'histones H2A/H2B pour l'assemblage des nucléosomes. Notre objectif est de caractériser la structure et la fonction du complexe de Nap1-H2A/H2B. Ainsi nous nous sommes tout d'abord intéresse à la stoechiometrie de ce complexe. Nous avons trouvé qu'un dimère de Nap1 s'associe à un dimère H2A/H2B (Nap1_2-H2A/H2B). D'autre part, l'analyse par spectrométrie de masse non-dénaturante a montré que ce complexe de base peut s'oligomériser et contenir jusqu'à 6 copies de Nap1_2-H2A/H2B. L'analyse de ce complexe par spectrométrie de masse non-dénaturant a montré que ce complexe peu oligomériser dans un grand complexe contenant jusqu'à 6 copies de Nap1_2-H2A/H2B. Nous avons également obtenu la première structure cristalline à basse résolution de ce complexe. L'analyse du même complexe par microscopie électronique à coloration négative a révélé la présence en solution du même oligomère que dans l'unité asymétrique du cristal, qui contient aussi 6 copies de Nap1_2-H2A/H2B. Ainsi, nous avons pu mettre en évidence de nouvelles interfaces d'interaction entre les différents composants de ce complexe qui nous permettent de mieux comprendre le processus d'assemblage des nucléosomes. Le remodelage de la chromatine permet l'expression des gènes eucaryotes. Ce remodelage nécessite des enzymes telles que des histone acétyltransférases (HAT) et les chaperons d'histones. Les HATs acétylent les chaînes latérales des lysines. Il a été proposé que les HATs et les histones chaperons agissent en synergie pour moduler la structure de la chromatine pendant la transcription. La HAT p300 a été proposé d'interagir avec l'histone chaperon Nap1. Nous avons entrepris de caractériser cette interaction. Malheureusement, nos expériences n'ont pas pu détecter d'interaction directe entre ces protéines. / Assembly of chromatin is an essential process that concerns most DNA transactions in eukaryotic cells. The basic repeating unit of chromatin are nucleosomes, macromolecular complexes that consist of a histone octamer that organizes 147 bp of DNA in two superhelical turns. Although, the structures of nucleosomes are known in detail, their assembly is poorly understood. In vivo, nucleosome assembly is orchestrated by ATP-dependent remodelling enzymes, histone-modifying enzymes and a number of at least partially redundant histone chaperones. Histone chaperons are a structurally diverse class of proteins that direct the productive assembly and disassembly of nucleosomes by facilitating histone deposition and exchange. The currently accepted model is that nucleosome assembly is a sequential process that begins with the interaction of H3/H4 with DNA to form a (H3/H4)2 tetramer-DNA complex. The addition of two H2A/H2B dimers completes a canonical nucleosome. High-resolution structures of histone chaperons in complex with H3/H4 histones have resulted in detailed insights into the process of nucleosome assembly. However, our understanding of the mechanism of nucleosome assembly has been hampered by the as yet limited number of co-crystal structures of histone–chaperone complexes. In particular it remains unclear how histone chaperons mediate H2A/H2B deposition to complete nucleosome assembly. In this work, we have investigated the role of the H2A/H2B chaperon Nap1 (Nucleosome assembly protein 1) in nucleosome assembly. We have determined the crystal structure of the complex between Nap1 and H2A/H2B and analysed the assembly by various biophysical methods. The structure shows that a Nap1 dimer binds to one copy of H2A/H2B (Nap1_2-H2A/H2B). A large ~550 kDa macromolecular assembly containing 6 copies of the Nap12-H2A/H2B complex is seen in the asymmetric crystallographic unit. We confirmed by both non-denaturing mass spectroscopy and negative stain electron microscopy studies that this assembly is the predominant form of the Nap1_2-H2A/H2B complex in solution. We further investigated the potential interplay between p300-mediated histone acetylation and nucleosome assembly. Together, the structure and associated functional analysis provide a detailed mechanism for the Nap1 chaperon activity, its role in H2A/H2B deposition and in nucleosome assembly.

Crystallization is often a major bottleneck to macromolecular structure determination. This is particularly true for membrane proteins, which have hydrophobic surfaces that cannot readily form crystal contacts. Of the roughly 109,000 protein structures in the PDB, only about 539 represent unique membrane proteins, despite immense interest in membrane proteins from both a biological and therapeutic standpoint. Membrane protein crystallization has been facilitated by the development of new detergents, lipidic cubic phase methods, soluble protein chimeras, and non-covalent protein complexes. The design process of protein fusion constructs and non-covalent antibody fragments specific for each target membrane protein, however, is costly and time-consuming. An improved, more general method of membrane protein co-crystallization is needed. This dissertation details the development of two approaches for cost-effective non-covalent crystallization chaperones: (1) Engineered hypercrystallizable Fab antibody fragment with high affinity for EYMPME (EE epitope), which form complexes with EE-tagged soluble and membrane proteins. (2) Engineered monomeric streptavidin (mSA2) for complexation with biotinylated membrane proteins. Both methods are generalizable through insertion of a short epitope into a surface-exposed loop of a membrane protein by site directed mutagenesis. Crystallization trials of representative chaperone-membrane protein complexes and possible difficulties with the approach are discussed.

Orientador: Carlos Henrique Inácio Ramos / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-26T13:20:36Z (GMT). No. of bitstreams: 1 Murakami_LeticiaMariaZanphorlin_D.pdf: 5383539 bytes, checksum: 1a45d203e6e3c5a992791b8ce893aa36 (MD5) Previous issue date: 2014 / Resumo: Chaperonas moleculares e proteínas de choque térmico (Heat shock protein, Hsp) atuam contra a agregação e o enovelamento incorreto de proteínas, que são os agentes causais de doenças neurodegenerativas, como por exemplo, Alzheimer e Parkinson. A Hsp90 é uma das mais importantes chaperonas moleculares, considerada essencial para a viabilidade celular em eucariotos, pois está associada com a maturação de proteínas atuantes na sinalização e ciclo celular. Além disso, foi demonstrado que a Hsp90 está envolvida na estabilização do fenótipo tumoral de diversos tipos de câncer, destacando a sua importância biomédica. A interação com co-chaperonas, proteínas auxiliares das chaperonas, permite que a Hsp90 atue como uma proteína "hub", ou seja, um ponto central de regulação de diversas proteínas. Muitas dessas co-chaperonas possuem um ou mais domínios do tipo TPR (do inglês, tetratricopeptide repeat) que interagem com o C-terminal da Hsp90. No presente projeto de doutorado, investigamos as características estruturais e termodinâmicas da interação entre o domínio C-terminal da Hsp90 (C-Hsp90) e a co-chaperona TPR Tom70 humana, utilizando técnicas de reação-cruzada acoplada à espectrometria de massas (LC-MS/MS), calorimetria de titulação isotérmica (ITC), espalhamento de raios-X à baixos ângulos (SAXS) e modelagem molecular. Os resultados de LC-MS/MS e ITC evidenciaram novas regiões na interação do complexo C-Hsp90/Tom70 que envolve a hélice A7 presente na Tom70 e experimentos de SAXS revelaram a estrutura em baixa resolução das proteínas C-Hsp90, Tom70 e do complexo C-Hsp90/Tom70. Além disso, investigamos o efeito do celastrol, um composto com potencial atividade anti-câncer, na conformação e na função da Hsp90. Na presença do composto, a Hsp90 sofre um processo de oligomerização e a natureza dos oligômeros foi determinada por ferramentas bioquímicas e biofísicas, tais como espalhamento dinâmico de luz (DLS), cromatografia de exclusão molecular analítica acoplada a espalhamento de luz em multiângulos (SEC-MALS) e eletroforese em gel nativo. Interessantemente, a oligomerização induzida pelo celastrol não afetou a atividade de proteção da Hsp90 contra a agregação protéica e a capacidade de ligação as co-chaperonas com enovelamento tipo TPR. Este é o primeiro trabalho a apontar um possível mecanismo para a ação do celastrol sobre a Hsp90. Coletivamente, nossos resultados e descobertas contribuem para uma melhor compreensão dos mecanismos moleculares relacionados à interação entre chaperonas e co-chaperonas, bem como, chaperonas e potenciais ligantes. / Abstract: Molecular chaperones and heat shock proteins (Hsp) act against protein aggregation and misfolding, which are the causal agents of neurodegenerative diseases such as Alzheimer and Parkinson. Hsp90 is one of the most important molecular chaperones, considered essential for cell viability in eukaryotes, since it is associated with the maturation of proteins involved in cell cycle and signaling. In addition, it was demonstrated that Hsp90 is implicated in the stabilization of the tumor phenotype of various types of cancer, highlighting its biomedical importance. The interaction with co-chaperones, auxiliary proteins of chaperones, allows that Hsp90 acts as a hub, being a central point for regulation of several other proteins. Many of these co-chaperones have one or more TPR domains that interact with the C-terminus of Hsp90. In this PhD project, we investigated structural and thermodynamic characteristics of the interaction between the C-terminus domain of Hsp90 (C-Hsp90) and the TPR co-chaperone human Tom70, using techniques of cross-linking coupled with mass spectrometry (LC-MS/MS), isothermal titration calorimetry (ITC), small angle X-ray scattering (SAXS) and molecular modeling. The results of LC-MS/MS and ITC revealed new regions involved in the interaction of the C-Hsp90 with Tom70, which encompasses the A7 helix from Tom70, and SAXS experiments unveiled the low resolution structure of the proteins C-Hsp90, Tom70 and the C-Hsp90/Tom70 complex. In addition, we investigated the effect of celastrol, a compound with a potential anti-cancer activity, on the conformation and function of Hsp90. In the presence of celastrol, Hsp90 undergoes oligomerization and the nature of the oligomers was determined by biochemical and biophysical tools such as dynamic light scattering (DLS), size-exclusion chromatography coupled to multi-angle light scattering (SEC-MALS) and native gel electrophoresis. Interestingly, the celastrol-induced oligomerization did not affect the protective activities of Hsp90 against protein aggregation or the capacity to bind TPR co-chaperones. This is the first study to point out a possible mechanism for the action of celastrol on Hsp90. Collectively, our findings contribute to a better understanding of the molecular mechanisms associated to the interaction between chaperones and co-chaperones, as well as chaperones and potential ligands / Doutorado / Quimica Organica / Doutora em Ciências