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A DNA double-strand break repair and it's disorders with a relationship to the cancerogenesis
Komžák, Josef ; Ševčík, Jan (advisor) ; Vopálenský, Václav (referee)
The DNA-double strand break (DSB) repair has an essential importance for the genomic integrity maintenance. The main DSB repair pathways are homologous recombination (HR), non-homologous end joining (NHEJ) and single-strand annealing (SSA). The most important protein factors contributing to the maintenance of genomic integrity by direct participation in DSB repair are MRN, ATM, Rad51, BRCA1/2 and PALB2 in the case of HR; Ku70/80 DNA-PKcs, XRCC4 and DNA ligase IV in the case of NHEJ and Msh2-Msh3 and Rad1- Rad10 in the case of SSA. If mutated, these proteins can cause the inability to repair DNA lesions leading to a malignant transformation. The predominant phenotype manifestation of BRCA1/2 inactivation is the hereditary breast and/or ovarian cancer (HBOC). Mutations in ATM have been described as a cause of ataxia telangiectasia and inactivation of NBN gene (Nbs1 protein) causes the Nijmegen breakage syndrome. Other syndromes connected with defects in a DSB repair pathways are Fanconi anemia and Werner syndrome. Detail knowledge of DSB repair process is a mandatory for diagnostics and effective therapy of a number of malignances. An example of practical and clinically relevant utilization of current knowledge about the DSB repair process is the concept of a synthetic lethality as a specific therapy. This...
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The use of parallel sequencing methods in microbiology.
Pavlíková, Magdaléna ; Najmanová, Lucie (advisor) ; Vopálenský, Václav (referee)
The thesis describes the history of development of sequencing methods with special focus on the modern effective parallel sequencing methods and their application in microbiology. The development and improvements of sequencing systems lead to the acceleration of the process and considerable decrease of price, which consequently allow wider spectrum of applications. Each of the sequencing systems has its characteristic features including drawbacks stemming from the principle of the respective method. Not every method suitable for all the applications. In the thesis the sequencing methods are compared and examined with respect to their appropriateness for certain application fields in microbiology. The currently available sequencing methods are usually categorized into three "generations", distinguished by sets of typical features. First generation methods include the systems of Sanger and Maxam-Gilbert; "next generation" is represented by methods 454, Illumina, SOLiD and Helicos; and finally SMRT, Ion Torrent and the commercially not yet available nanopore sequencing are usually called "next-next generation". Now the sequencing becomes a standard technology of molecular biology, not only in the basic microbiological research, but it is also widely applied in medicine (quick identification of patogenes,...
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Variability of the IRES elements of the hepatatis C virus
Zeman, Jakub ; Vopálenský, Václav (advisor) ; Španielová, Hana (referee)
Hepatitis C virus (HCV) has an internal ribosomal binding site (IRES) located near the 5ʹ end of its genome. The HCV IRES is capable of direct binding to the 40S small ribosomal unit and eukaryotic initiation factor eIF3, and can initiate translation after the assembly of the whole 80S ribosome. Various molecular types can act as IRES inhibitors. Small molecule compounds seem to be the most promising agent for use in the clinic. The main objective of the thesis was to develop a system for searching for small molecule compound inhibitors of HCV IRES in a library of chemical compounds. Several variants of vector carrying bicistronic cassettes were prepared. After validating their functionality by transient transfection of mammalian cell cultures, mammalian stable cell lines were established. These stable cell lines will allow for automatization of the search for small molecule compound inhibitors of HCV IRES. Our second objective was to study the variability of HCV IRES sequences in patient samples. The samples were analysed by temperature gradient gel electrophoresis (TGGE). Select specimen were sequenced, cloned into a vector with bicistronic cassette and analysed by flow cytometry. In this was we evaluated the effect of specific mutations in the HCV IRES sequence on the level of IRES dependent...
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Characterization of transcription apparatus encoded by the linear plasmids of the yeast Kluyveromyces lactis
Sýkora, Michal ; Vopálenský, Václav (advisor) ; Krásný, Libor (referee)
Transcription is an essential step in the expression of genetic information. This process depends on protein complex of multisubunit RNA polymerases that are exceptionally conserved among all cellular organisms. These enzymes together with eukaryotic RNA-dependent RNA polymerases involved in gene silencing form a monophyletic protein family whose members contain two double-ψ β-barrel structural motifs in their active center. This family also includes a group of mainly in silico predicted non-canonical DNA-dependent RNA polymerases which differ from multisubunit RNA polymerases in reduced composition. Putative non-canonical RNA polymerase consisting of two subunits is also encoded by cytoplasmic linear plasmids of the yeast Kluyveromyces lactis and highly likely transcribes genes of these plasmids. Characterization of a unique transcription machinery of Kluyveromyces lactis plasmids with major emphasis on non-canonical RNA polymerase has become the aim of this work. Bioinformatic analysis in silico was used to examine the evidence leading to an assumption of existence of specific RNA polymerase. Subsequent genetic and biochemical methods were used for: 1) production of putative RNA polymerase subunits in several expression systems; 2) testing interaction between several components of transcription...
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Molecular analysis of resistance gene vga(A)LC identification of key aminoacid residues.
Kroová, Michaela ; Najmanová, Lucie (advisor) ; Vopálenský, Václav (referee)
Protein Vga(A) gives staphylococci resistance to streptogramins A. The recently discovered protein Vga(A)LC differs from Vga(A) only by 7 amino acid residues, but this difference is sufficient for shift of its substrate specificity towards lincosamides. The group of four amino acids in the central part of protein (LGAG in Vga(A) and SVTS in Vga(A)LC) was detected to be crucial for the substrate specificity. In this diploma thesis 5 alternativesets of vga(A)LC gene point mutations were prepared in order to determine the impact of individual amino acids of the aforementioned group on the resistance phenotype. Mutations were prepared in vector pGEM® -T and cloned into shuttle vector pRB374. The prepared constructs were transformed by electroporation into the sensitive strain of Staphylococcus aureus RN4220 and values of minimum inhibitory concentration (MIC) were measured for lincomycin, clindamycin and pristinamycin IIA by the agar dilution method. The transformation was not successful in one of the mutations. Results of setting MIC for the remaining four mutations do not make it possible to specify uniquely the ratio of individual amino acids for determining substrate specificity. Two of the amino acids were found to be important. We anticipate preparation of more mutations.
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Artificial lipid membranes and the properties of the membrane proteins.
Valášek, Ján ; Fišer, Radovan (advisor) ; Vopálenský, Václav (referee)
Cell membrane and membrane proteins play fundamental roles in cell life. Cells use transporters and ion channels to interact with the environment and maintain cellular homeostasis. Therefore, their understanding and characterization are important area of basic and applied research. Large size of the cell and membrane protein insolubility make hamper their study and requires more sophisticated approaches, e.g. for the research of individual channels and transporters. This work seeks to create a simple overview of the most used methods for creating artificial lipid membranes. They are LB film, DIB, BLM and SLB. They can be examined by applying lipid bilayer and individual proteins. The work also outlines the procedure for the preparation, use and benefits of different approaches and briefly describes the membrane proteins, biological membranes and conventional methods for their study.
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Novel hepatitis C virus proteins
Zeman, Jakub ; Vopálenský, Václav (advisor) ; Horníková, Lenka (referee)
The hepatitis C virus (HCV) is a major etiological agent of chronic liver diseases. More than 170 million people worldwide are chronically infected, and more than 100 thousand of them develop hepatocellular carcinoma a year. HCV is an enveloped, positive-sense single-stranded RNA virus (+ssRNA virus) of the family Flaviviridae. Its genome is translated to produce a single polyprotein precursor that is further processed by cellular and viral proteases to form 10 viral proteins. Moreover, there is another protein encoded in an alternative reading frame. Two alternative translation mechanisms have been proposed for expression of this alternative reading frame protein (ARFP): a frameshift mechanism and translation initiating from internal start codons. Despite ten years of research its role in vivo is not yet explained. It appears that secondary structures in the core encoding region of HCV genome but not ARFP expression are required for robust viral translation and replication. The results of recent studies suggest that mutations distorting these structures may result not only in slowing down the viral cycle but also in a brand new and utterly unusual serological profile in patients as well as an increased level of expression of ARFP.
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Catalytic function of DNA-dependent RNA polymerases
Sýkora, Michal ; Vopálenský, Václav (advisor) ; Lichá, Irena (referee)
DNA-dependent RNA polymerase is a highly organised protein complex that is responsible for gene expression and its regulation. Multisubunit RNA polymerase with its several catalytic activities is responsible for transcription of genes to RNA copies in all cellular organisms. During transcription RNA polymerase undergoes substantial conformational changes depending on the conditions in a particular cell. RNA polymerase in a state designated as an elongation complex passes through repetitive cycles of adding a nucleotide to the growing RNA chain. The active center contains two magnesium ions which coordinate the reactive groups of substrates. Furthermore, the active center contains structural elements that participate in binding of substrate, propper orientation of substrate towards the template strand and translocation of the RNA polymerase. The most important of these mobile structural elements are the bridge helix and the trigger loop whose conformational changes accompanies nucleotide addition cycle. Advances in the structural and biochemical characterization of RNA polymerase open new possibilities in the understanding of the transcription mechanism, its fidelity and control.
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delta subunit of bacterial RNA pol and its role in regulation of gene expression in B. subtilis
Dvořáček, Lukáš ; Krásný, Libor (advisor) ; Vopálenský, Václav (referee)
Delta subunit of bacterial RNA pol and its role in regulation of gene expression in B. subtilis. In this work I focus on regulation of eubacterial gene expression. First, I describe recent knowledge about a key stage of gene expression - transcription, focusing on regulation of trancription iniciation via small effector molecules (guanosine tetraphosphate, initiating nucleoside triphosphate) that are important for the regulation of ribosomal RNA. Second, in the experimental part of my work, I focus on the role of the _ protein, a subunit of RNA polymarase in gram positive bacteria, in transcription iniciation and its effects on regulation of RNA polymerase by the concentration of initiating nucleoside triphosphates.
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