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Major structural protein of Polyomaviruses: Interactions with host cell structures
Mrkáček, Michal ; Horníková, Lenka (advisor) ; Němečková, Šárka (referee)
The main structural protein VP1 is the product of late polyomaviral genes and it is the largest and the most abundant protein of the whole polyomaviral capsid. Because of the low coding capacity of the polyomaviral genomes, it is considered that in addition to its structural role the VP1 protein might have some additional functions in the late phase of the infectious cycle. This diploma thesis is exactly on these additional functions. In the case of the VP1 protein of mouse polyomavirus, it was observed that the protein is capable of binding to the structure of cellular microtubules. The first objective of this work was to test whether pentamers of the VP1 protein are able of this binding without the participation of other cellular (or viral) proteins. Based on an in vitro experiment, we showed that protein VP1 binds to the structure of microtubules very inefficiently. The second objective of this work was to prepare a detection system that would allow an identification of potential interaction partners of BK polyomavirus VP1 protein. Therefore, expression plasmids producing the N and C-terminally tagged VP1 protein were prepared. These tagged proteins had the property of being biotinylated whilst being produced in the transfected cells. By using affinity chromatography, the entire protein complexes...
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Mechanisms of superinfection exclusion by animal viruses
Vlachová, Štěpánka ; Horníková, Lenka (advisor) ; Šmahel, Michal (referee)
Viral interference can be found in both homologous and heterologous viruses and may have significant impact on the infection. One of such impacts is superinfection exclusion, which is a defence mechanism used by a wide variety of viruses. The superinfection exclusion may occur in different steps of viral life cycle. Despite being a common viral function, most of the mechanisms of exclusion stay yet undefined, same as proteins, which are taking part in superinfection exclusion. This work is a summary of knowledge in the field of interference between animal viruses, with focus on homologous interference and mechanisms of superinfection exclusion. Research of this phenomenon can bring important information for the development of new antiviral treatment, virus diagnosis and understanding of interactions between viruses. Key words: Viral infection, animal viruses, homologous interference, superinfection exclusion, mechanisms of exclusion
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Role of molecular chaperones Hsp70 and Hsp90 in the replication cycle of DNA viruses
Žáčková, Sandra ; Horníková, Lenka (advisor) ; Poláková, Ingrid (referee)
Molecular chaperones are proteins which enable other proteins to assemble into native conformation and are essential for viability of the cells. Chaperones of the Hsp70 family bind to newly synthetized and denaturated proteins, prevent their aggregation and facilitate their assembly. They participate in assembly and disassembly of oligomers and also in the transport across the membranes. Chaperones of the Hsp90 family do not participate in the assembly of nascent or denaturated proteins. They bind proteins which are nearly in native conformation and enable them to assemble into conformation suitable for ligand binding or interacting with other proteins. These attributes predestinate chaperones to participate in the replication cycle of DNA viruses. A huge amount of proteins is translated during viral infection. These proteins require the chaperones to facilitate their assembly and are also required for assembly into oligomers and macromolecular structures. In addition to capsid assembly the chaperones also participate in transport of genetic information to the sites of replication, disassembly of incoming viral particles or replication of viral DNA. Therefore, the development of specific chaperone inhibitors is a promising approach. They could be used against broad spectrum of viral infections...
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Evolution of host specificity in avian influenza
Divín, Daniel ; Vinkler, Michal (advisor) ; Horníková, Lenka (referee)
Avian influenza is a dangerous viral disease, which threats animals and people's health and nowadays evokes great concerns linked with pandemic threat. Veterinary procedures tries to limit spreading of infection by eradication of all birds nearby the outbreak place of the disease to limit as much economic damage as possible. However, there is obvious considerable variability in susceptibility, course and transmission of the disease in different species. In model species (Anas platyrhynchos f. domestica a Gallus gallus f. domestica), we can see a big difference in course of the disease linked with different equipment of immunity genes. There is fragmented information about other species. The main aim is therefore to summarize knowledge about avian influenza, it's origin, evolution, diversity, spreading in environment and susceptibility of different species to this disease.
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Interaction of hepatitis B virus proteins with mechanisms of innate immunity
Vávrová, Petra ; Hirsch, Ivan (advisor) ; Horníková, Lenka (referee)
Specific aim of this bibliographic research is to elucidate interaction of hepatitis B virus proteins with mechanisms of the innate immunity. The work will specially analyze the role of viral proteins before and after their transport from the infected cell. Because of the central role of cccDNA for virus persistence in human organism, the work will study the effects of restriction factors on its possible destruction and eradication. The research will be focused on the effect of viral proteins during acute, chronic and occult infection.
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The role of posttranslational modifications of minor proteins and acetylation of microtubules in mouse polyomavirus infection
Mariničová, Zuzana ; Horníková, Lenka (advisor) ; Saláková, Martina (referee)
Mouse polyomavirus (MPyV) capsid is composed of the main capsid protein VP1 and minor capsid proteins VP2 and VP3. Minor proteins are not essential capsid assembly, but they are key for efficient viral infection. The first part of this thesis studies the modifications of VP2 and VP3, the deamidation of Asn at 253 of VP2 (137 of VP3) and N-terminal acetylation of Ala of VP3, which could be the cause of double bands for VP2 and VP3 on SDS-PAGE. Mutated genomes of MPyV N253D (Asn to Asp) and N253E (Asn to Glu) simulating deamidation and A117V (Ala to Val) with reduced acetylation were prepared previously. We prepared three isolations of the mutant viruses and we confirmed that the deamidation is the cause of the double bands. Mutant viruses were compared to the wild type in terms of efficiency of infection, but the role of deamidation could not be proven. Virus A117V is noninfectious either due to lowered acetylation or the substitution of amino acid at this position. This thesis also studies the role of -tubulin acetylation in the infection of MPyV. The role of -tubulin acetylation in viral infection is being investigated to find new antiviral strategies. Acetylation rises after MPyV infection, but this is not due to a change in mRNA expression of tubulin acetylating (TAT1) or deacetylating enzyme...
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Significance of MHC class I molecules in antitumor immunity
Lhotáková, Karolína ; Poláková, Ingrid (advisor) ; Horníková, Lenka (referee)
The main function of the major histocompatibility complex class I (MHC I) glycoproteins is to present antigenic peptides to CD8+ T lymphocytes. Majority of the peptides displayed by this complex come from cell protein degradation and CD8+ T lymphocytes do not respond to them. Tumor development leads to alterations in protein production and new epitopes are generated which impacts peptide repertoire presented by MHC I glycoproteins on the cell surface. Peptides originated from tumor antigens activate CD8+ T lymphocytes and induce anti-tumor immune responses. Decreased surface expression of MHC I molecules is a common phenomenon in tumor cells that prevents effective immune response. As appropriate MHC I expression level on tumor cells is needed for their effective killing by T cell-mediated immune response, downregulation of the MHC I expression may lead to the selection of tumor cells with decreased MHC I level. This downregulation can be either reversible or irreversible, affecting not only the expression of genes encoding the light and heavy chains of MHC I molecules, but also genes of the antigen-processing machinery (APM). Immunotherapeutics focused on the induction of surface expression of MHC I molecules often have other unfavorable impacts on the immune system. Therefore, a new approach is...
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