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ADP-ribosylation in ARH3-deficient cells and its impact on cellular functions
Kuttichová, Barbora ; Hanzlíková, Hana (advisor) ; Valihrach, Lukáš (referee)
ADP-ribosylation is a crucial post-translational modification that regulates various cellular processes, including DNA repair. It is catalysed by poly-ADP-ribose polymerases (PARPs) and involves the transfer of ADP-ribose moieties from the redox cofactor NAD+ to proteins, including histones. To maintain cellular homeostasis, ADP-ribose chains need to be rapidly degraded by ADP-ribosyl glycohydrolases. While poly-ADP-ribose glycohydrolase (PARG) is highly efficient, it cannot cleave the terminal ADP-ribose moiety. For the removal of the terminal mono-ADP-ribose, two glycohydrolases, TARG1 and ARH3, are involved. This removal process is necessary because it enables DNA repair factors to access the site of DNA damage. The primary goal of this thesis is to characterise cells derived from patients with homozygous ARH3 mutations and to develop appropriate tools to improve our understanding of the molecular mechanism by which ARH3 mutations affect ADP-ribosylation and how it contributes to the onset of the associated neurological disease. To achieve this, I measured the levels of ARH3 protein and detected increased mono-ADP-ribosylation in ARH3-mutated patient-derived fibroblasts. Furthermore, I assessed the sensitivity of these cells to different PARP inhibitors, which hold potential for the therapeutic...
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The source of endogenous DNA damage in neurodegenerative disease
Havelková, Jarmila ; Hanzlíková, Hana (advisor) ; Vodička, Pavel (referee)
DNA single-strand breaks (SSBs) are amongst the most frequent DNA lesions arising in cells and can threaten genetic integrity and cell survival, as indicated by the elevated genetic deletion, embryonic lethality and neurological disease observed when single-strand break repair (SSBR) is attenuated. One of the proteins important for rapid repair of SSBs is XRCC1, which is a molecular scaffold protein that interacts with multiple DNA repair enzymes (e.g. PARP1, PNKP, POLβ, APTX, LIG3) and thus, promotes their stability and/or function. Defects in SSBR have been associated with hereditary neurodegeneration in humans, cerebellar ataxias and seizures. Here, I focus on genetic disease spinocerebellar ataxia autosomal recessive-26 (SCAR26), which has been shown to be linked to mutations in XRCC1. I investigate the amount of XRCC1 protein in XRCC1-defective cells and reveal that cells from patients with mutations in XRCC1 exhibit greatly reduced XRCC1 levels. I show that reduced levels of XRCC1 protein in cells correlate with the increasing number of endogenous SSBs, measured by quantification of ADP-ribose in the chromatin. In addition, I confirm that the most endogenous SSBs arise in S phase of the cells cycle during replication. Moreover, I prove that the main sources of the endogenous SSBs in...
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The impact of mutant huntingtin on oxidative stress in primary fibroblasts isolated from a new Huntington's disease knock in porcine model
Sekáč, Dávid ; Ellederová, Zdeňka (advisor) ; Hanzlíková, Hana (referee)
Huntington's chorea is a dominantly inherited disease caused by trinucleotide (Cytosine-Adenine -Guanine) expansion in a gene coding huntingtin protein. Carriers of these mutation show symptoms associated with motor impairment, a cognitive and psychiatric disturbance, which is called Huntington's disease (HD). The major sign of HD is striatal atrophy in the middle age of life. Since it is known that huntingtin protein participates in a lot of cellular processes, such as transcriptional regulation and metabolism, these processes change by its mutation. One of the features observed in HD pathogenesis is the presence of oxidative stress. The aim of the work was to monitor the molecular changes preceding the HD manifestation in the knock-in minipig model. As a material for monitoring molecular changes leading to this condition, primary fibroblasts were used. Whereas, the oxidative stress arises from an imbalance between oxidants and antioxidants, level of reactive species and lipid peroxidation together with expression of antioxidant response associated genes was measured. At the same time, expression of metabolic and DNA repair related genes was monitored. Although the differences in oxidative stress level or the expression of antioxidative response genes were not detected, the changes in the...
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Molecular mechanisms of genome integrity maintenance under conditions of replication stress
Boleslavská, Barbora ; Dobrovolná, Jana (advisor) ; Hanzlíková, Hana (referee) ; Šebesta, Marek (referee)
Precise and timely duplication of chromosomal DNA is an essential process for all dividing cells. Failure to complete this process can lead to cell death or irreversible changes in genetic information ultimately leading to cell transformation and cancer. The sophisticated multiprotein complex ensuring DNA replication is often slowed down or stalled by numerous obstacles, including DNA lesions and secondary DNA structures, but also by another vitally important cellular process - by ongoing DNA transcription. Head-on transcription-replication collisions (TRCs) associated with the formation of R-loop structures are the major endogenous source of genomic instability. R-loops are three-stranded nucleic acid structures composed of an RNA:DNA hybrid and displaced DNA strand, with a strong potential to halt replication fork progression and to have a genotoxic effect. To ensure complete DNA replication, the eukaryotic cells have developed various mechanisms for removal and overcoming the obstacles to replication fork progression. However, despite the extensive research, the molecular mechanisms underlying the restart of R-loop-stalled replication forks remain unclear. Here, we provide evidence that in human cells the restart of DNA synthesis at the sites of TRCs is a multi-step process involving fork...
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Genomic instability associated with formation of RNA:DNA hybrids and molecular mechanisms of its suppression
Naščáková, Zuzana ; Dobrovolná, Jana (advisor) ; Hanzlíková, Hana (referee) ; Šolc, Petr (referee)
One of the most common infections of a human organism is an infection of stomach induced by pathogenic bacteria Helicobacter pylori (H. pylori). It is estimated that every second person is infected, with even higher prevalence in developing countries. As a quiet enemy, H. pylori can colonise a human stomach for decades without manifestation of infection-associated symptoms. However, chronic infection may cause severe damage to the stomach tissue, subsequently leading to the development of gastric diseases, including gastritis and ulcer disease. H. pylori infection is also a driving cause of gastric cancer, with 80% of gastric cancers being associated with chronic infection. H. pylori ensures its life-long persistence in a human host organism via the action of its virulence factors, which have a pleiotropic effect on multiple systems, mostly acting on the attenuation of a human immune system and the induction of atrophy of stomach tissue. The irreversible changes of stomach epithelium are induced by activation of an innate immune response in H. pylori-exposed epithelial cells through the stimulation of ALPK1/TIFA/NF-κB signalling pathway upon a recognition of β-ADP heptose, an intermediate product of bacterial lipopolysaccharide biosynthesis, and consequently leading to the formation of DNA...
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Defects in DNA repair and RNA metabolism associated with human neurological disorders
Cihlářová, Zuzana ; Hanzlíková, Hana (advisor) ; Čermák, Lukáš (referee) ; Roithová, Adriana (referee)
The human genome is constantly under the attack by various damaging agents, leading to the breakage of one or both strands of DNA that might interfere with RNA processing. Importantly, our cells have evolved diverse mechanisms to rapidly repair various DNA lesions, highlighting the importance of genetic integrity. Defects in DNA repair and/or RNA metabolism can lead to a variety of human hereditary diseases, with pathologies including growth and developmental defects, immunodeficiency, predisposition to cancer, and neurodegeneration. Mutations in the BRAT1 (BRCA1-associated ATM activator-1) protein have been associated with neurological disorders characterized by heterogenous phenotypes with varying levels of clinical severity ranging from microcephaly, hypertonia, epilepsy, seizures, and early death in the first two years of life to mild cerebellar atrophy and ataxia. Previously, BRAT1 protein has been implicated in the cellular response to DNA double-strand breaks and ATM signalling. However, the exact mechanism/s by which mutations in BRAT1 gene trigger neurological disorders are largely unknown. Recently, we have identified a homozygous missense c.185T>A (p.Val62Glu) variant in BRAT1 that markedly reduced the level of BRAT1 protein in patient-derived cell lines. Surprisingly, our data show that...
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Role of the MRN complex in the nucleolar DNA damage response
Palková, Natálie ; Macůrek, Libor (advisor) ; Hanzlíková, Hana (referee)
Genome integrity maintenance is crucial for proper functioning and survival of all organisms, especially if the cell is constantly exposed to various genotoxic agents. For that reason, there are specific mechanisms that detect DNA damage, facilitate signalling and promote repair of the damaged region. These processes are referred to as DNA damage response (DDR). Necessary part of the DDR is also the MRE11-RAD50-NBS1 complex (MRN), comprised of the nuclease MRE11, ATPase RAD50 and regulatory docking protein NBS1. The MRN complex has an indispensable role in the detection and immediate resection of double-strand breaks (DSBs), signal transduction and activation of ataxia telangiectasia mutated (ATM) kinase with its downstream effectors necessary for the DDR. The compounds of the MRN complex are involved in processes crucial for efficient DNA repair, cell survival and maintenance of genomic stability. The main aim of this work is to elucidate less known functions of the MRN complex in the nucleoli, nuclear membrane-less organelles formed around the copies of genes coding rRNA. This work discusses how the MRN complex is involved in the repair of rDNA double-strand breaks, transient inhibition of rRNA transcription or nucleolar segregation. Thereafter, this work puts into context the latest knowledge in...
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Effects of variability of weather and temperature extremes on cardiovascular diseases.
Hanzlíková, Hana
Elevated mortality represents one of the main impacts of temperature extremes on human society. Increases in cardiovascular mortality during heat waves have been reported in many European countries; much less is known about which particular cardiovascular disorders are most affected during heat waves, and whether similar patterns are found for morbidity (hospital admissions). Relatively less understood is also cold-related mortality and morbidity in winter, when the relationships between weather and human health are more complex, less direct, and confounded by other factors such as epidemics of influenza/acute respiratory infections. This thesis comprises a collection of four papers, three of which address the impacts of extreme temperatures on cardiovascular disease (CVD) in the population of the Czech Republic with a focus on ischaemic heart disease (IHD) and cerebrovascular disease (CD). The three papers are complemented by a study analysing trends in cardiovascular mortality and hospitalisations in the Czech Republic. The first paper focuses on comparing the effects of hot and cold spells on mortality from CVD in the population of the Czech Republic during 1986-2006 and examines differences between population groups. The second paper analyses effects of hot and cold spells on IHD mortality in...
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Genomic instability associated with formation of RNA:DNA hybrids and molecular mechanisms of its suppression
Naščáková, Zuzana ; Dobrovolná, Jana (advisor) ; Hanzlíková, Hana (referee) ; Šolc, Petr (referee)
One of the most common infections of a human organism is an infection of stomach induced by pathogenic bacteria Helicobacter pylori (H. pylori). It is estimated that every second person is infected, with even higher prevalence in developing countries. As a quiet enemy, H. pylori can colonise a human stomach for decades without manifestation of infection-associated symptoms. However, chronic infection may cause severe damage to the stomach tissue, subsequently leading to the development of gastric diseases, including gastritis and ulcer disease. H. pylori infection is also a driving cause of gastric cancer, with 80% of gastric cancers being associated with chronic infection. H. pylori ensures its life-long persistence in a human host organism via the action of its virulence factors, which have a pleiotropic effect on multiple systems, mostly acting on the attenuation of a human immune system and the induction of atrophy of stomach tissue. The irreversible changes of stomach epithelium are induced by activation of an innate immune response in H. pylori-exposed epithelial cells through the stimulation of ALPK1/TIFA/NF-κB signalling pathway upon a recognition of β-ADP heptose, an intermediate product of bacterial lipopolysaccharide biosynthesis, and consequently leading to the formation of DNA...
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The source of endogenous DNA damage in neurodegenerative disease
Havelková, Jarmila ; Hanzlíková, Hana (advisor) ; Vodička, Pavel (referee)
DNA single-strand breaks (SSBs) are amongst the most frequent DNA lesions arising in cells and can threaten genetic integrity and cell survival, as indicated by the elevated genetic deletion, embryonic lethality and neurological disease observed when single-strand break repair (SSBR) is attenuated. One of the proteins important for rapid repair of SSBs is XRCC1, which is a molecular scaffold protein that interacts with multiple DNA repair enzymes (e.g. PARP1, PNKP, POLβ, APTX, LIG3) and thus, promotes their stability and/or function. Defects in SSBR have been associated with hereditary neurodegeneration in humans, cerebellar ataxias and seizures. Here, I focus on genetic disease spinocerebellar ataxia autosomal recessive-26 (SCAR26), which has been shown to be linked to mutations in XRCC1. I investigate the amount of XRCC1 protein in XRCC1-defective cells and reveal that cells from patients with mutations in XRCC1 exhibit greatly reduced XRCC1 levels. I show that reduced levels of XRCC1 protein in cells correlate with the increasing number of endogenous SSBs, measured by quantification of ADP-ribose in the chromatin. In addition, I confirm that the most endogenous SSBs arise in S phase of the cells cycle during replication. Moreover, I prove that the main sources of the endogenous SSBs in...
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