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Epigenetic regulation of gene expression in cancer progression and HIV-1 latency
Kovářová, Denisa ; Hejnar, Jiří (advisor) ; Černá, Marie (referee) ; Rösel, Daniel (referee)
Epigenetic mechanisms of transcriptional regulation and modulation of gene expression using RNA interference have become a powerfull tool for studying various cellular mechanisms, including tumor progression and viral latency. Advances in expression profiling have provided technology to detect candidate genes implicated in this complex process and bring other possibilities in the diagnosis and treatment of tumor diseases. In this work, I compare the gene expression profiles of v-src-transformed metastatic and nonmetastatic cells using microarray chip technology. Transcription factor homeodomain only protein X (HOPX) was identified as one of the differentially expressed genes. Activity of HOPX gene in several cancer types is usually controlled by promoter methylation. The role HOPX in metastatic formation was assessed by inoculation of cells with modulated expression of HOPX in a syngeneic chicken model system. After HOPX knockdown using shRNA, originally metastatic line showed decreased in vivo metastatic capacity. Further genomic analyses identified a cadre of genes affected by HOPX knockdown. These data demonstrate that HOPX is a metastasis-associated gene and that its knockdown decreases the metastatic activity of v-src-transformed cells through altered gene expression patterns. In the second...
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Studies of properties of viral capsid proteins and development of recombinant vaccines and diagnostic components based on artificial viral structures
Fraiberk, Martin ; Forstová, Jitka (advisor) ; Hubálek Kalbáčová, Marie (referee) ; Hejnar, Jiří (referee)
The aim of this study was to develop a system for easy production of different veterinary chimeric vaccines based on stable mouse polyomavirus (MPyV) structures. The system is designed for antigens that are problematic in production or stability. First, universal vectors for baculovirus-directed production of chimeric MPyV VLPs or pentamers based on the major capsid protein VP1 were designed to be exploited as vaccines against other pathogens. The different strategies used in this study are based on: A) exposure of selected immunogenic epitopes on the surface of MPyV VLPs by inserting them into a surface loop of the VP1 protein, B) insertion of foreign protein molecules inside the VLPs, or C) fusion of a foreign protein or its part with the C-terminus of VP1 protein, thus forming giant pentamers of a chimeric protein. Candidate vaccine antigens against porcine circovirus 2 (PCV2), the causative agent of porcine circovirus 2 systemic diseases (PCV2-SD) which causes significant economic losses in swine breeding, were prepared using the constructed vectors. All candidate vaccines induced the production of antibodies against the capsid protein of PCV2 after immunization of mice. The candidate vaccine Var C based on fusion of MPyV and PCV2 capsid proteins, is able to induce production of antibodies with...
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The expression of miRNA in HPV-associated and HPV-independent head and neck tumors
Vojtěchová, Zuzana ; Tachezy, Ruth (advisor) ; Hejnar, Jiří (referee) ; Slabý, Ondřej (referee)
Head and neck cancers represent a group of tumors with two different etiologies. The first type is associated with the viral HPV infection, the second one is virus-independent and it is associated with smoking and alcohol consumption as two main risk factors. Numerous studies show that HPV-positive tumors are more frequent in younger patients, as well as that the prognosis and overall survival of these patients is remarkably better. Therefore, the modification of the treatment is considered. For this, however, specific, sensitive and clinically relevant biomarkers for accurate identification of tumor etiology is needed. Suitable candidates for such biomarkers are miRNAs, small non-coding regulatory molecules stable in archived samples, that have been shown as differentially expressed in human cancers and the expression pattern seems specific for tumors of different origin. The submitted thesis focuses on miRNA profiling in HPV-positive and HPV-negative tonsillar tumors and cervical carcinomas with the aim to find out the differences between regulation of important carcinogenetic pathways of tumors of viral and non-viral etiology. Our data have shown very large heterogeneity of the miRNA expression profiles of these tumors. Despite the well characterized and uniform samples collection, we have found...
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Alterations of the oncogenic properties of tumor cell lines by modulating oncogene expression. Example of v-src transformed chicken cell lines
Kovářová, Denisa ; Hejnar, Jiří (advisor) ; Španielová, Hana (referee)
4 Alterations of the oncogenic properties of tumor cell lines by modulating oncogene expression. Example of v-src transformed chicken cell lines Abstract v-Src protein tyrosine kinase is the product of the transforming gene transduced by avian Rous sarcoma virus. In contrast to proto-oncogene c-src, v-src lacks the negative-regulatory C-terminal domain and consequently shows a higher level of activity and transforming ability. In addition, v-Src contains point mutations throughout its coding region that probably contribute to the high level of intrinsic kinase activity. Long terminal repeats (LTR) comprise strong promoter-enhancer sequences and ensure efficient expression of the v-src gene. v-Src protein has a strong transforming potential in vitro and induces tumor development and growth in vivo. Moreover, it is implicated in metastatic formation. In several cancer types the elevated c-Src kinase activity caused pleiotropic cellular responses inducing transformation and metastasis. The aim of this diploma work was to reveal the role of v-Src in mediating tumor and metastatic progression in chicken cell lines PR9692 and PR9692-E9. Despite the low propensity of the chicken cells to immortalization, comparatively high immoratlization efficiency was observed in cells from ex vivo tumours growing progressively...
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Genomic preferences in integration and expression of retroviruses and retrovirus-derived vectors
Miklík, Dalibor ; Hejnar, Jiří (advisor) ; Žíla, Vojtěch (referee)
Integration and provirus establishment are the key steps of retroviral life cycle. Genome-wide studies show that the integration is not a random process and that groups of related retroviruses display distinguishable patterns of integration preferences. The most rated genomic features forming the integration preferences of retroviruses are transcription units, transcription start sites and CpG islands. Whereas extending knowledge of genome structure, new, mainly epigenetic marks, which have a relationship to retroviral preferences are being defined. The integration into a specific genome region has a straight influence on the provirus expression and therefore on the production of virus progeny. While integration into some regions results in provirus silencing which is managed and maintained by variety of factors, some other genomic regions are vice-versa capable of stable provirus expression maintenance. These findings have implications for construction of safe and efficient retroviral vectors as well as for use of modified retroviruses as markers for an epigenetic and expression profile determination of genome regions.
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Modulation of human telomerase activity by nucleoside and nucleotide analogues
Hájek, Miroslav ; Votruba, Ivan (advisor) ; Fajkus, Jiří (referee) ; Hejnar, Jiří (referee)
CONCLUSIONS Considering human telomerase as a promising target of anti-cancer therapy, the thesis deals with the study of inhibitory potency of selected ANP diphosphates towards telomerase, and the capability of nucleoside-type DNA methylation inhibitors to inhibit hTERT expression, knowing that hTERT expression closely correlates with telomerase activity in vitro and in vivo. The results can be summarized as follows: All the purine ANP diphosphates except for (S)-PMPApp and 6-Me2PMEDAPpp show dose- dependent inhibition of human telomerase in cell-free assay, the adenine derivatives are less effective inhibitors than the guanine derivatives. The only two pyrimidine ANP diphosphates tested (PMECpp and PMETpp) do not show any significant inhibitory potency towards telomerase. Activity of tested ANPs on telomerase is limited to their diphosphates (ANPpp) only. (R)-enantiomers are more inhibitory compared to (S)-enantiomers. This indicates that absolute configuration plays an important role in the telomerase inhibition and that the enzyme distinguishes between the (R)- and (S)-enantiomers. PMEGpp is the most potent human telomerase inhibitor among all ANPs studied with the IC50 value of 12.7 ± 0.5 mol.l-1 at 125 M dNTPs. Its inhibitory potency towards telomerase is comparable to that of ddGTP (IC50...
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Structural and regulatory aspects of Src kinase activation
Koudelková, Lenka ; Brábek, Jan (advisor) ; Brdička, Tomáš (referee) ; Hejnar, Jiří (referee)
Src kinase plays a crucial role in a multitude of fundamental cellular processes. Src is an essential component of signalling pathways controlling cellular proliferation, motility or differentiation, and is often found deregulated in tumours. Src activity is therefore maintained under stringent and complex regulation mediated by SH3 and SH2 domains and the phosphorylation state of tyrosines 416 and 527. Active Src adopts an open conformation whereas inactive state of the kinase is characterised by a compact structure stabilised by inhibitory intramolecular interactions. We identified phosphorylation of tyrosine 90 within binding surface of SH3 domain as a new regulatory switch controlling Src kinase activation. Using substitutions mimicking phosphorylation state of the residue we demonstrated that tyrosine 90 phosphorylation controls Src catalytic activity, conformation and interactions mediated by the SH3 domain, representing a positive regulatory mechanism leading to elevated activation of mitogenic pathways and increased invasive potential of cells. Based on correlation between compactness of Src structure and its catalytic activity, we constructed a FRET-based sensor of Src conformation enabling to measure the dynamics of Src activation in cells with spatio-temporal resolution. We found that...
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