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Unravelling molecular mechanisms of the abasic crosslink DNA repair
Hušková, Andrea ; Šilhán, Jan (advisor) ; Bařinka, Cyril (referee) ; Pavlíček, Jiří (referee)
4 Abstract DNA as the primary carrier of genetic information guarantees organisms to live, grow, develop and reproduce. However, this most vital molecule in the cell is subject to various damages every moment. If it is not repaired, the cell and the organism will eventually succumb to inevitable destruction. One of the most serious damages is abasic site interstrand crosslink (Ap-ICL). Ap-ICL is formed spontaneously when an abasic site covalently pairs with an adenine on the opposite strand. The lack of information on repair mechanisms, the influence of the local sequence and its stability leads to questions about the fate, toxicity and occurrence of these lesions in cells. During evolution, several mechanisms have evolved to repair these and other damages to ensure the organism's survival. A recently discovered pathway known to repair Ap-ICL is named after the DNA glycosylase responsible for removing Ap-ICL. NEIL3 DNA glycosylase is recruited to Ap-ICL by ubiquitylation of DNA helicase, which is part of the DNA replication complex. NEIL3 glycosylase contains several zinc-finger domains, that bind to the damaged DNA and ensure its catalytic function. The molecular mechanism of the NEIL3 glycosylase repair process is currently not known. In order to answer the aforementioned unknowns, the rate of formation,...
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Software Keyboard for Android
Šilhan, Jan ; Šolony, Marek (referee) ; Zachariáš, Michal (advisor)
The aim of this bachelor thesis is to create a unique software keyboard for Android framework. First part of the thesis is the overview of current keyboards on the market, where I also mention a difference between them and my concept. In the next chapter I describe how the pattern of custom keyboard works and what components I used to build the application. After that I explain my steps during the process of implementation and how I solved particular problems. Finally I deduce usability, possible expand of keyboard among the Android users and potential future features.
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Unified Software Database for RPM Based Systems
Šilhan, Jan ; Očenášek, Pavel (referee) ; Zelený, Jan (advisor)
V GNU/Linuxovém prostředí je nepřeberné množství možností, jak instalovat aplikace. V dnešní době existuje spousty nástrojů, které mají na starost různé části systému. Linuxové distribuce mají hlavního správce balíčků a populární programovací jazyky mají také vlastního správce balíčků. Všechny tyto nástroje si udržují informace o nainstalovaném softwaru, a proto si každý z nich spravuje vlastní databázi s redundantními metadaty o balíčcích. Záměrem této práce je analyzovat úložné prostory, identifikovat případy užití správců balíčků v distribuci Fedora a následně navrhnout a implementovat jednotnou cen- trální softwarovou databázi na systému.
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Effect of selected compounds on NMPylation of nsp9 SARS-CoV-2 catalyzed by NiRAN domain of nsp12 SARS-CoV-2
Fedák, Michal ; Šilhán, Jan (advisor) ; Vaněk, Ondřej (referee)
SARS-CoV-2 pandemic that begun in the end of 2019 caused over 770 milion confirmed cases of infection and almost 7 milion deaths worliwide. Despite pandemic being suppressed thanks to vaccines and restriction measures, the research of new medication targeting this virus continues. One of the possible targets of SARS-CoV-2 is nonstructural protein 9 (nsp9), which is essential for virus repliation. Just recently it was revealed that this protein can covalently bind nukleoside monophosphate (NMPylation) or RNA chain of various length (RNAylation). These reactions are catalyzed by nidovirus RNA-dependent RNA polymerase (RdRp) asociated nucleotidyltransferase (NiRAN) domain of nonstuctural protein 12 (nsp12). RNAylation of nsp9 showed to be crucial step in synthesis of RNA cap. The function of NMPylation was not jet revealed, but it is believed that this modification of nsp9 could play a role in priming of RNA synthesis. Some studies have already investigated inhibition of NMPylation. In this diploma thesis recombinant nsp9 was prepared and used in NMPylation reactions. Negative effect of DMSO on nsp9 NMPylation was observed. Three compounds (saquinavir, darunavir and conivaptan) selected based on the results of in silico studies did not show ability to inhibit NMPylation of nsp9. Next, it was confirmed...
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Mechanistic insights into alcohol-induced interstrand crosslink repair by the nuclease SLX4-XPF-ERCC1
Havlíková, Jana ; Šilhán, Jan (advisor) ; Lux, Vanda (referee)
Alcohol ranks among the most widely used recreational drugs in the world, even though it is considered a risk factor for more than 200 diseases. The primary negative impact of alcohol lies in its metabolite, acetaldehyde, which, as a highly reactive compound, can form mutagenic adducts and interstrand crosslinks (ICLs) in DNA. The formation of ICLs, which have a covalent nature and block the separation of the two DNA strands during replication, is one of the important causes of mutagenesis and carcinogenesis. To maintain genomic stability, repair mechanisms have evolved. One of them is a pathway that uses proteins encoded by Fanconi anaemia genes, whose defects lead to the disease of the same name. Defects in repair pathways can be particularly dangerous in individuals with impaired functionality in other metabolic pathways, such as alcoholics and individuals with mutations in genes that result in the accumulation of toxic acetaldehyde. The theoretical part of this thesis deals with alcohol metabolism, in vivo acetaldehyde formation, and its interactions with DNA. The ICL and their repair pathways are characterized in more detail. A separate chapter is dedicated to Fanconi anaemia. The practical part of this work focuses on the preparation of site-specific acetaldehyde- induced ICL (AA-ICLs) and the study...
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Cloning, expression and characterization of the viral proteins
Pekárek, Matěj ; Šilhán, Jan (advisor) ; Obšil, Tomáš (referee)
Over the last twenty years three new coronavirus strains have appeared in human population, that cause dangerous infections of respiratory tract. At this moment no approved drug exists, that could mitigate the infection caused by these viruses. One of the possible targets of these drugs are proteins responsible for viral genome replication. Nsp13 is primarily a helicase, that unwinds double stranded nucleic acids in the direction of 5'-3', but it also increases activity of replication and transcription complex, it participates in the synthesis of 5' cap on viral RNA and it probably mediates the backtracking of replication and transcripton complex during the process of RNA repair. On top of that nsp13 is strongly conserved among all coronaviruses and it is possible target not only for COVID-19 treatment, but also infections caused by potential future coronaviruses. Theoretical part of the thesis briefly describes the life cycle of SARS-CoV-2, functions of individual proteins of this virus, that participate in replication and transcription of RNA and it summarizes current knowledge about function of nsp13 and its potential inhibitors. In experimental part we have prepared the expression vector for nsp13, that was used for the production of nsp13. Nsp13 was then isolated and purified. (In Czech) Key...
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Molecular mechanisms and functions of 14-3-3 proteins
Šilhán, Jan ; Obšil, Tomáš (advisor) ; Krůšek, Jan (referee) ; Schneider, Bohdan (referee)
Závěr Hlavním cílem této doktorské práce bylo objasnění molekulárních mechanismů funkce 14-3-3 proteinů a vlivu na proteiny FOXO4 a tyrosinhydroxylasu. V první časti této práce (publikace I) byla potvrzena předložená hypotéza polohy Cterminálního konce molekuly 14-3-3. Bylo ukázáno, že v nepřítomnosti ligandu se Cterminální konec nachází ve vazebném místě a brání tak vstupu ligandů. Po vazbě fosforylovaných ligandů, dochází k velmi silné vazbě a vytěsnění C-terminálního konce 14-3- 3 proteinu z vazebného místa. Tyto výsledky jsou v souladu s původními pracemi, které navrhly důležitost tohoto segmentu jako inhibitoru nepatřičných ligandů. Druhá část této doktorské práce poskytuje rozsáhlý popis vlivu 14-3-3 proteinů na transkripční faktory FOXO4. S použitím stacionární a časově-rozlišené fluorescence byla studována interakce 14-3-3 proteinu s fosforylovaným transkripčním faktorem FOXO4. Navázání 14-3-3 proteinu způsobuje rozpad komplexu FOXO4:DNA. Tato část práce charakterizuje interakci 14-3-3 proteinu s DNA-vazebnou doménou FOXO4. Výsledky neprokázaly výrazné konformační změny v rámci DNA-vazebné domény. Spíše dochází ke sterickému bránění vazby DNA (publikace II). Ve třetí části se práce zabývá studiem interakcí 14-3-3 s fosforylovaným ligandem odvozeným od C-konce enzymu serotonin N-acetyltransferasa...
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Structure and molecular mechanisms of DNA repair by Nei glycosylase
Landová, Barbora ; Šilhán, Jan (advisor) ; Lux, Vanda (referee)
Abasic sites (Ap site, from apurinic/apyrimidinic) are one of the most common lesions generated in DNA by spontaneous base loss or DNA repair processes. There are two equilibrating forms of an Ap site - ring-open aldehyde and cyclic hemiacetal. Ring- opened aldehydes are reactive electrophilic groups capable of formation covalent adduct with nucleophilic sites in DNA. DNA interstrand cross-link (ICL) resulting from the Ap sites is formed spontaneously as a covalent bond between ring-open aldehyde and amin group of adenin residue in the opposite strand of double stranded DNA. ICLs block DNA replication and transcription. The formation of Ap site derived ICL is relatively long process taking several hours. We assume that the ring-opening of an abasic site is the rate-limiting step in the formation of the thermodynamic ICL. However, formation, stability and DNA repair of Ap-ICL are still poorly understood processes. Here, I have set up mechanistic in vitro experiments to reveal and calculate the probability of Ap-ICl formation in vivo. In more detail, I study the rates of formation of Ap-ICLs in the sequence context of neighbouring nucleotides of freshly formed covalent bond of ICL. I focus on sequence preference, the influence of AT/ GC rich regions and the length of oligonucleotides. I have...
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