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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
141

The ABC of KRAB zinc finger proteins

Looman, Camilla January 2003 (has links)
<p>All living organisms consist of cells and the identity of a cell is defined by the genes it expresses. To assure proper function, a cell receives continuous information on which genes to turn on and off. This information is, to a large extent, provided by transcription factors. Krüppel-related zinc finger proteins probably constitute the largest family of transcription factors in mammals and many of these proteins carry a potent repressor domain called Krüppel-associated box (KRAB). The human genome alone encodes more than 200 KRAB zinc finger proteins but still very little is known about their biological functions. </p><p>The Krüppel-related zinc finger genes appear to have been involved in a massive expansion throughout evolution. To unravel some of the secrets underlying this evolutionary success, we studied the molecular evolution of KRAB zinc finger genes. We show that the frequently occurring duplications of these genes are accompanied by a low sequence constraint in their zinc finger region. In addition, we show that the number of zinc finger motifs carried within these proteins is far from fixed. New zinc finger motifs are frequently added while others are inactivated or even discarded from the coding region. The structurally independent Krüppel zinc finger motif has, through these mechanisms, served as a highly adaptive building block for the generation of new transcriptional regulators. </p><p>The mouse, rat and human genomes carry four different variants of the KRAB domain – KRAB(AB), KRAB(Ab), KRAB(AC) and KRAB(A). This thesis presents the identification of a novel KRAB domain, KRAB C, as well as a functional analysis of the different KRAB domains. We conclude that all different KRAB domains share a common co-repressor, TIFβ, and effectively repress transcription. These functions are mainly mediated by the KRAB A box but are clearly influenced by the presence of a KRAB B, b or C box. Furthermore, we show that all KRAB zinc finger gene subfamilies originate from the KRAB(AB) zinc finger genes.</p><p>In addition, this thesis includes a structural and functional analysis of four novel mouse and human KRAB zinc finger genes; <i>MZF6D</i>, <i>HKr18</i>, <i>HKr19</i> and <i>HZF12</i>. Whereas <i>HKr18</i> and <i>HZF12</i> seem to be ubiquitously expressed, <i>MZF6D</i> and <i>HKr19</i> show a more restricted expression pattern. Northern blot and <i>in situ</i> hybridisation analyses of <i>MZF6D</i> showed that the expression of this gene is restricted to meiotic germ cells. <i>MZF6D</i> might thus be involved in the formation of male gametes. The expression of <i>HKr19</i>, on the other hand, seems to be restricted to lymphoid cells, indicating a possible role for this KRAB zinc finger gene in the regulation of lineage commitment.</p>
142

Characterisation of CtBP : A Co-Repressor of Transcription that Interacts with the Adenovirus E1A Protein

Sundqvist, Anders January 2001 (has links)
In this study, adenovirus E1A has been used to target and analyse the transcriptional function of the cellular C-terminal Binding Protein (CtBP). Transcription is a complex biochemical process that represents a major regulatory step in gene expression. Formation of condensed chromatin by histone deacetylation and inhibition of efficient assembly of the transcription machinery are hallmarks of transcriptional repression. During a virus infection, an extensive modulation of the host cell gene expression in favour of viral gene expression can be observed. For example, the transcription regulatory E1A protein from adenovirus has been proven to be a valuable research-tool in characterising cellular proteins controlling eukaryotic gene expression. Expression of a CtBP-binding peptide, encoded by the second exon of E1A, de-repressed transcription from a broad range of promoters, suggesting that CtBP functioned as a repressor of transcription. Artificial promoter recruitment of CtBP, by using different Gal4-fusion proteins, confirmed that CtBP functioned as a repressor. Repression of transcription by Gal4E1A-recruited CtBP was efficiently prevented by a CtBP binding competent E1A peptide, indicating that E1A relieved CtBP mediated repression by displacing CtBP from the promoter. Furthermore, Gal4CtBP repressed both basal and activated transcription in a distance dependent manner, suggesting that CtBP might repress transcription by interfering with the assembly of the basal transcription machinery. Interestingly, CtBP was found to interact with histone deacetylase-1 (HDAC-1) both in vivo and in vitro and endogenous CtBP could also recruit histone deacetylase activity. This might indicate that histone deacetylation was involved in CtBP mediated repression. However, Gal4CtBP mediated repression was insensitive to inhibition of histone deacetylase activity, suggesting an alternative function of HDAC-binding in CtBP mediated repression. In conclusion, this work demonstrates that CtBP can act as a general repressor of activated and basal transcription. Furthermore, although CtBP was shown to recruit histone deacetylase activity the relevance of this binding remains unclear.
143

Three Subfamilies of KRAB Zinc Finger Proteins : A Structural, Functional and Evolutionary Analysis

Mark, Charlotta January 2003 (has links)
Krüppel-related zinc finger proteins constitute the largest single class of transcription factors within the human genome. Members of this protein family have the ability to either activate or repress transcription depending on the presence of specific activator or repressor domains within the protein. Approximately one third of the Krüppel-related zinc finger proteins contain an evolutionarily well-conserved repressor domain termed the KRAB domain. This domain acts as a potent repressor of transcription by interacting with the co-repressor protein, TIF1β. TIF1β then, in turn, recruits HP1 proteins, HDACs and probably other proteins involved in gene silencing. In order to identify novel KRAB-containing zinc finger proteins, one mouse monocytic cDNA library and two testis cDNA libraries were screened for novel members of this multigene family. Six novel KRAB-ZNF cDNAs, four mouse and two human, were isolated. The corresponding proteins were all shown to contain N-terminally located KRAB domains as well as varying numbers of C-terminally located zinc finger motifs. An extensive comparative sequence analysis of the KRAB domains of these proteins together with KRAB domains from a large number of previously identified KRAB-ZNF proteins resulted in a clear subdivision into three different subfamilies, A+B, A+b and A. Later, we also isolated a fourth KRAB box, which is present downstream of the KRAB A box in a few proteins of the KRAB A family. This module was named KRAB C. Potential functional differences between these different subfamilies were investigated. In line with previous observations, the KRAB A box was shown to repress transcription, an activity which was enhanced by the presence of the KRAB B box. However, addition of neither the KRAB b box nor the KRAB C box had any effect on repression. Moreover, all KRAB A motifs had the ability to bind TIF1β, and this binding was increased both by the presence of the KRAB B box and by the KRAB C box. The KRAB b box, however, did not seem to contribute to TIF1β-binding. One of the novel human cDNAs, HKr19, was found to be a member of the large ZNF91 family of KRAB zinc finger genes. Interestingly, the expression of HKr19 and a number of other closely related genes were restricted to lymphoid cells, indicating that these genes may be involved in regulating lineage commitment. The effect of HKr19 on cell viability was investigated by transfection into human embryonic kidney cells (HEK 293). The results indicated that HKr19, or its zinc finger domain in isolation, were toxic to these cells when expressed at high levels. The MZF6D protein, on the other hand, showed a testis-specific expression. In situ hybridization analysis located this expression to meiotic germ cells, suggesting a role for this protein in spermatogenesis. Further, the evolutionary perspectives of this large gene family were addressed, and its enormous expansion throughout evolution probably includes numerous duplication events. The results from two extensive sequence analyses give clues to how the repetitive nature of the ZNF motif has given rise to both internal duplications of single motifs as well as duplications of entire genes resulting in gene clusters.
144

The ABC of KRAB zinc finger proteins

Looman, Camilla January 2003 (has links)
All living organisms consist of cells and the identity of a cell is defined by the genes it expresses. To assure proper function, a cell receives continuous information on which genes to turn on and off. This information is, to a large extent, provided by transcription factors. Krüppel-related zinc finger proteins probably constitute the largest family of transcription factors in mammals and many of these proteins carry a potent repressor domain called Krüppel-associated box (KRAB). The human genome alone encodes more than 200 KRAB zinc finger proteins but still very little is known about their biological functions. The Krüppel-related zinc finger genes appear to have been involved in a massive expansion throughout evolution. To unravel some of the secrets underlying this evolutionary success, we studied the molecular evolution of KRAB zinc finger genes. We show that the frequently occurring duplications of these genes are accompanied by a low sequence constraint in their zinc finger region. In addition, we show that the number of zinc finger motifs carried within these proteins is far from fixed. New zinc finger motifs are frequently added while others are inactivated or even discarded from the coding region. The structurally independent Krüppel zinc finger motif has, through these mechanisms, served as a highly adaptive building block for the generation of new transcriptional regulators. The mouse, rat and human genomes carry four different variants of the KRAB domain – KRAB(AB), KRAB(Ab), KRAB(AC) and KRAB(A). This thesis presents the identification of a novel KRAB domain, KRAB C, as well as a functional analysis of the different KRAB domains. We conclude that all different KRAB domains share a common co-repressor, TIFβ, and effectively repress transcription. These functions are mainly mediated by the KRAB A box but are clearly influenced by the presence of a KRAB B, b or C box. Furthermore, we show that all KRAB zinc finger gene subfamilies originate from the KRAB(AB) zinc finger genes. In addition, this thesis includes a structural and functional analysis of four novel mouse and human KRAB zinc finger genes; MZF6D, HKr18, HKr19 and HZF12. Whereas HKr18 and HZF12 seem to be ubiquitously expressed, MZF6D and HKr19 show a more restricted expression pattern. Northern blot and in situ hybridisation analyses of MZF6D showed that the expression of this gene is restricted to meiotic germ cells. MZF6D might thus be involved in the formation of male gametes. The expression of HKr19, on the other hand, seems to be restricted to lymphoid cells, indicating a possible role for this KRAB zinc finger gene in the regulation of lineage commitment.
145

Häktad eller omedelbart omhändertagen? : en studie om akuta frihetsberövanden av unga lagöverträdare

Svensson, Lupita January 2006 (has links)
This thesis deals with the question of how Swedish society responds when juveniles commit crimes. The focus is social work co-operating with the legal system and the interaction between these two. The aim of this study is to make visible/analyse factors that affect the choice between treatment and correction of juveniles in an emergency situation, when there is a necessity to choose between immediate preventative custody on the one hand, and detention on the other. This study analyses the selection through outcome patterns. Theoretically the base is six concepts; system/practice, and treatment/correction. Together they form a model where the actors (the social services/the police/the attorney/county administrative courts/district courts) on this juvenile field can be situated. The strategies of the actors’ decision-making are implied by either norm-rational decision-making or goal-rational decision-making. Empirical data is studied through records of immediate custody and detention of juveniles aged 15-18 years old. The immediate denial of freedom represents, in the Swedish legislation, a process whereby social services and law enforcers meet and decide whether to treat or correct the juvenile. This selection is the focus of the empirical study of this thesis. In 1992, 1998 and 2003 a national overall survey was made of all juveniles aged 15-18 years that have been either in immediate custody or in detention or both. Documentation was obtained from the courts. The results show that the general denial of freedom of juveniles have increased greatly during the years 1992, 1998 and 2003, and especially from 1998 to 2003. Almost all of the acts concern boys, even though girls are making at break-through in 2003. There are differences between the groups that either have been in detention or in immediate custody in ways of “survey-year”, “ethnic background”, “age” and “categorising of crime”. This study shows a large discrepancy between legislation and the legal practice.
146

Fibromyalgia and self-regulatory patterns : development, maintenance or recovery in women

Wentz, Kerstin January 2005 (has links)
Aims: The overall aim of this thesis was to elucidate psychological processes and development, maintenance or recovery related to fibromyalgia based on in depth interviews. In a next step women with fibromyalgia, women without long-lasting pain and women with long-lasting pain were compared using psychometric instruments selected or developed based on qualitative results. Methods: Twenty-one women with fibromyalgia and 8 women recovered were interviewed. Their narrations were analysed using Grounded Theory. Tentative theory was built. The I Myself Scale (IMS) was constructed to mirror self-regulation prior to onset of symptoms and complemented with an instrument on current self-regulation: Structural Analysis of Social Behaviour (SASB) and SF-36 mirroring health related quality of life, regarding the two pain groups. The groups were compared using analysis of variance, principal components analysis paired with discriminant analysis and profile analysis. Results: Analyses of the interviews resulted in core concepts of an “unprotected self” (current fibromyalgia) or a “strong but not enough to be weak” self (recovery). Data patterns indicated that the women as children were unprotected in relation to stimuli and affects. Relationships with the parents were characterised by strain and low levels of support. The recovery group had as children simultaneously been able to develop obvious competence and capability to receive help. Psychological vulnerability was in adult life compensated for through pronounced helpfulness and dissociation/repression including intense activity. An increase in mental load such as localised pain or psychosocial crisis preceded onset of fibromyalgia accompanied by impaired cognitive functioning. The state of fibromyalgia meant maintained high levels of mental load such as difficulties of the selfstructures, impaired cognitive functioning and somatic symptoms. The recovery group experienced substantial social support and often used mastering strategies to ease symptoms. A decrease in strain as improved life conditions and cease of overexertion preceded recovery. Health was thereafter maintained through careful management as seeking low levels of strain and pacing of activity. Recovery ‘on parole’ also meant personal growth and use of efficacious defences. Psychometrical testing confirmed qualitative data patterns of self-regulation connected to fibromyalgia. Impaired selfreference/ understanding of health needs and others not being asked for help and advice was reported before onset of symptoms. Dissociation or repression including intense activity and self-loading were also employed. SASB and SF-36 indicated that women with fibromyalgia experienced higher levels of mental “load” than the other pain group. Conclusion: Qualitative data indicated that life prior to onset of fibromyalgia and current fibromyalgia held qualities of impaired self-regulation in relation to mental and physical load. The state of recovery relied on improved self-regulation allowed by conditions of life. Quantitative data patterns confirmed qualitative results on impaired self-protection before onset of fibromyalgia and a specifically high level of mental load during the state of fibromyalgia. Psychological disregulation is discussed and hypothesised to cause but also later in the process parallel alterations in somatic homeostatic functions. Recovery could mean that biological regulation regarding strain is replaced with more of “psycho-social” regulation as careful pacing of work. Implications for treatment are suggested.
147

The role of retrograde repression in limiting axonal regeneration in the central nervous system

Wu, Adam Sauh Gee 24 April 2008
The regenerative capacity of mature mammalian CNS neurons after axonal injury is severely limited by a variety of mechanisms. Retrograde repression is the continuous inhibition of the expression of growth phenotypes by tonic signals produced by target tissues and transmitted to the neuron cell body via retrograde axonal transport. Loss of target contact through axonal injury is thought to interrupt this retrograde signal and allow the up-regulation of growth-associated proteins. Most CNS neurons, however, possess many widespread axon collaterals, such that retrograde repression is maintained by intact sustaining collaterals even if some axons are injured.<p>In this project we investigated whether or not retrograde repression plays a role in limiting the expression of GAP-43 in transcallosal neurons. Because TCNs possess local axon collaterals to nearby cortex and project distal axons to homologous areas of contralateral cortex, we hypothesized that the simultaneous interruption of retrograde repressive signals from both ipsilateral and contralateral cortex would result in an up-regulation of GAP-43 expression in at least some TCNs.<p>We found that a bilateral infusion of a function blocking antibody to FGF-2 into the parietal cortex of rats using implanted osmotic mini-pumps resulted in a significant increase in the level of expression of GAP-43 mRNA in TCNs identified by retrograde fluorescent labeling. In contrast, neither ipsilateral or contralateral antibody infusions alone increased GAP-43 expression significantly compared to controls. The level of expression of GAP-43 in TCNs did not significantly increase after stereotactic callosotomy alone, but callosotomized animals treated with an ipsilateral infusion of anti-FGF-2 had levels of increased GAP-43 expression equivalent to those seen in animals that had received bilateral antibody infusions.<p>We conclude that FGF-2 provides a retrograde repressive signal for at least some mature mammalian TCNs, and that the expression of growth-associated proteins can be up-regulated in CNS neurons by simultaneously blocking retrograde repressive signals from all existing axon collaterals. The ability to alter the gene expression of mature CNS neurons in both normal and injured states through the targeted infusion of a pharmacological agent may have potential clinical implications in the future.
148

The "Infernal World": Imagination in Charlotte Brontë's Four Novels

Cassell, Cara MaryJo 02 May 2007 (has links)
If you knew my thoughts; the dreams that absorb me; and the fiery imagination that at times eats me up and makes me feel Society as it is, wretchedly insipid you would pity and I dare say despise me. (C. Brontë, 10 May 1836) Before Charlotte Brontë wrote her first novel for publication, she admitted her mixed feelings about imagination. Brontë’s letter shows that she feared both pity and condemnation. She struggled to attend to the imaginative world that brought her pleasure and to fulfill her duties in the real world so as to avoid its contempt. Brontë’s early correspondence attests to her engrossment with the Angrian world she created in childhood. She referred to this world as the “infernal world” and to imagination as “fiery,” showing the intensity and potential destructiveness of creativity. Society did not draw Brontë the way that the imagined world did, and in each of Brontë’s four mature novels, she recreated the tricky navigation between the desirable imagined world and the necessary real world. Each protagonist resolves the struggle differently, with some protagonists achieving more success in society than others. The introduction of this dissertation provides critical and biographical background on Brontë’s juxtaposition of imagination/desire and reason/duty. Sandra Gilbert and Susan Gubar’s The Madwoman in the Attic supplies the basis for understanding the ways that the protagonists express imagination, and John Kucich’s Repression in Victorian Fiction defines the purposefulness of repression. The four middle chapters examine imagination’s manifestations and purposes for the protagonists. The final chapter discusses how the tension caused by the competing desires to express and repress imagination distinguishes Brontë’s style.
149

Fraudulent Elections, Political Protests, and Regime Transitions

Manukyan, Alla 14 December 2011 (has links)
This research studies protests after fraudulent elections in a collective action framework, examining the impact of the potential cost, benefit and likelihood of success of protest on the occurrence and intensity of protests. Quantitative analysis of fraudulent elections in about 100 countries from 1990 to 2004 shows that the odds of protest after fraudulent elections are greater when the level of state repression is moderate with a possible backlash effect of high repression, when the opposition is united, and when international monitors denounce election results. The analysis only partially supports the benefit of protest argument. Also, the research uses case studies from Eurasia (Armenia, Belarus, Georgia, and Russia) and mini-case studies from Africa and Latin America to study in more detail the effects of the factors identified in the quantitative analysis and to identify overlooked but important explanatory factors using a set of extensive interviews conducted in the United States and during fieldwork in Armenia, Georgia, and Russia with politicians, domestic and international election monitors, and country experts.
150

The role of retrograde repression in limiting axonal regeneration in the central nervous system

Wu, Adam Sauh Gee 24 April 2008 (has links)
The regenerative capacity of mature mammalian CNS neurons after axonal injury is severely limited by a variety of mechanisms. Retrograde repression is the continuous inhibition of the expression of growth phenotypes by tonic signals produced by target tissues and transmitted to the neuron cell body via retrograde axonal transport. Loss of target contact through axonal injury is thought to interrupt this retrograde signal and allow the up-regulation of growth-associated proteins. Most CNS neurons, however, possess many widespread axon collaterals, such that retrograde repression is maintained by intact sustaining collaterals even if some axons are injured.<p>In this project we investigated whether or not retrograde repression plays a role in limiting the expression of GAP-43 in transcallosal neurons. Because TCNs possess local axon collaterals to nearby cortex and project distal axons to homologous areas of contralateral cortex, we hypothesized that the simultaneous interruption of retrograde repressive signals from both ipsilateral and contralateral cortex would result in an up-regulation of GAP-43 expression in at least some TCNs.<p>We found that a bilateral infusion of a function blocking antibody to FGF-2 into the parietal cortex of rats using implanted osmotic mini-pumps resulted in a significant increase in the level of expression of GAP-43 mRNA in TCNs identified by retrograde fluorescent labeling. In contrast, neither ipsilateral or contralateral antibody infusions alone increased GAP-43 expression significantly compared to controls. The level of expression of GAP-43 in TCNs did not significantly increase after stereotactic callosotomy alone, but callosotomized animals treated with an ipsilateral infusion of anti-FGF-2 had levels of increased GAP-43 expression equivalent to those seen in animals that had received bilateral antibody infusions.<p>We conclude that FGF-2 provides a retrograde repressive signal for at least some mature mammalian TCNs, and that the expression of growth-associated proteins can be up-regulated in CNS neurons by simultaneously blocking retrograde repressive signals from all existing axon collaterals. The ability to alter the gene expression of mature CNS neurons in both normal and injured states through the targeted infusion of a pharmacological agent may have potential clinical implications in the future.

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