La transcription fidèle d’un gène lors de son activation nécessite l’assemblage d’un ensemble de protéines autour du promoteur. Parmi ces protéines, le complexe TFIIH joue un rôle central et important au travers de ses sous-unités enzymatiques. Des mutations dans les sous-unités XPB, XPD et p8/TTD-A de TFIIH conduisent à trois maladies autosomiques récessives distinctes : xeroderma pigmentosum (XP), parfois associés avec le syndrome de Cockayne (XP/CS) et la trichothiodystrophie (TTD). En étudiant différentes mutations dans ces trois sous unités de TFIIH, nous avons montré que chaque mutation analysée conduit à une dérégulation transcriptionnelle spécifique du gène RARβ2, gène cible des RAR. L’intégrité architecturale et enzymatique de TFIIH conditionne le bon recrutement du complexe TFIIH et également des facteurs de réparation par excision de nucléotides (NER). TFIIH muté perturbe leur recrutement et par conséquence compromet le remodelage de la chromatine médiée par les facteurs NER tels que les modifications post-traductionnelles (PTMs) des histones, l’induction des cassures de l’ADN, la déméthylation de l’ADN et les boucles de chromatine. Par conséquence, en plus de ses activités enzymatiques, TFIIH forme une plate-forme afin de recruter les facteurs NER et orchestres les fonctions connexes de la transcription. Cette pénétrance variable parmi les mutants donne lieu à un gradient de phénotype observé chez les patients TTD, XP ou XP/CS. / Fidelity in transcription of the gene requires assembly of set of proteins around the promoter,upon gene activation. The TFIIH complex is central among these proteins and plays a key role through its enzymatic subunits. Mutations in TFIIH subunits XPB, XPD and p8/TTD-A leads to three distinct autosomal recessive disorders: xeroderma pigmentosum (XP), sometimes associated with Cockayne’s syndrome (XP/CS) and trichothiodystrophy (TTD). By studying the different mutation in these three subunits of TFIIH from mentioned genetic disease models, we have shown that each mutation analyzed led to a specific transcriptional dysregulation of theRAR-target gene RAR 2. The architectural and enzymatic integrity of TFIIH condition the appropriate recruitment of TFIIH complex and further the arrival of the Nucleotide ExcisionRepair (NER) factors. By disturbing their recruitment, mutated TFIIH consequently compromised the chromatin remodeling mediated by NER factors such as histones posttranslational modifications (PTMs), DNA breaks induction, DNA demethylation and genelooping. Hence it can be concluded that in addition to its enzymatic activities, TFIIH provide a platform to recruit the NER factors and orchestrates the related functions in transcription. Such varying penetrance among mutants gives rise to a phenotype gradient as observed in TTD, XPor XP/CS patients.

Lors de la vie, des mécanismes de réparation de l’ADN sont mis en oeuvre lors d’agressions, pour protéger le génome. La réparation par excision de nucléotides (NER) est l’un de ces mécanismes. Des mutations des facteurs NER sont à l’origine de 3 maladies génétiques humaines: Xeroderma pigmentosum (XP), la trichothiodystrophie (TTD) et le syndrome de Cockayne (CS). Certains de leurs signes cliniques ne sont pas expliqués par un défaut de réparation de l’ADN. Des études suggèrent que ces facteurs interviennent dans d’autres processus, notamment lors de l’expression des gènes. Durant ma thèse, je me suis intéressé aux rôles des facteurs NER dans la transcription. En effet, j’ai montré que ces facteurs, dit de réparation, étaient recrutés avec la machinerie transcriptionnelle au niveau du promoteur et du terminateur de gènes activés. Ils influencent l’environnement chromatinien des gènes activés (boucles de chromatine et modifications post-­‐ traductionnelles des histones). Ma thèse apporte une meilleure compréhension du processus de transcription des gènes activés, permettant de mieux comprendre certaines anomalies associées aux yndromes XP, CS et TTD. / Throughout life, the mechanisms of DNA repair are implemented in attacks to protect the integrity of our DNA. The nucleotide excision repair (NER) is one of these mechanisms. Mutations targeting genes of NER factors (XPA-­‐G, TTD-­‐A, CSA and CSB) are responsible for three human genetic diseases : Xeroderma pigmentosum (XP), trichothiodystrophy (TTD) and Cockayne syndrome (CS). Some of them clinical features cannot be explained by a defect in DNA repair only. Previous studies suggest that these factors could be involved in other functions, including gene expression. In my thesis, I am interested in the roles of NER factors during the transcription process. Indeed, we have shown that these “repair” factors, were recruited with the transcription al machinery at the promoter and terminator of activated genes during transcription. They influence the chromatin environment of activated genes (chromatin loops and post-­‐translational modifications of histones).My thesis provides a better understanding of the transcription process of activated genes and allows a better understanding of some syndromes associated with XP, CS and TTD.

This study was an experimental design, using twenty-two variables, twelve covariates, and six criterion measures. The purpose of the study was the effect of the use of selected transcription drills in beginning shorthand on the ability of students to produce both typewritten copy and mailable letters from shorthand notes. The bases for comparison were five minute timed transcription tests, three-minute dictation tests, and thirty-minute mailable letter production tests, of both previewed and unpreviewed material.

Le travail se propose d’analyser sous divers aspects l’un des manuscrits les moins étudiés appartenant au célèbre groupe des manuscitsfranco-italiens provenant de la famille de Gonzaga de Mantou, l’Huon d’Auvergne, conservé à Berlin. La première partie du travail est une transcription interprétative intégrale du manuscrit : elle est complétée par une étude de l’écriture gothique et une analyse d’un riche ensemble d’enluminures (deuxième partie) à travers la comparaison avec un autre code contemporaine lui aussi en franco-italien, l’Entrée d’Espagne, conservé à Venise et d’autres mnuscrits illustrés réalisés en Italie du Nord au XIV siècle (en particulier le Roman de Troie). La troisième partie de la thèse traite de manière plus spécifique des questions stylistiques et linguistiques: en particulier, les analyses linguistiques concernant le lexique en isolant deux champs sémantiques, le champ du combat et celui de la mer. La partie linguistique est complété par un tableau des rimes qui suit l’ordre des laisses, par une table synoptique des rimes des deux poèmes (Huon d’Auvergne et Entrée d’Espagne) et par un dictionnaire de rimes des deux poèmes complets mis sur CD-Rom. / Using different analytic perspectives, this dissertation examines the Huon d’Auvergne manuscript, one of the less studied manuscripts from the famous group of the Franco-Italian codices in Berlin coming from a Gonzaga family. Other than a complete interpretative transcription of the manuscript, an early section of this work centers around the study of Gothic and the analysis of the rich decorative apparatus comparing it whit another manuscript of the same period written in Franco-Italian, the Entrée d’Espagne, kept in Venice, and other manuscripts written in Northern Italy in the 14th century (in particular the Roman de Troie). The second part of this thesis is more specifically devoted to literary, stylistic, and linguistic question : in particular, the analyses of the lexicon of the poem, compared with the one of Entrée d’Espagne, and the rhyme schemes which characterize it. A complete list of the rhyme schemes of Huon d’Auvergne and Entrée d’Espagne, included on a cd-Rom, will verify the analyses and considerations regarding the meter of the poem which will be fund in the chapter of the thesis focusing on this topic.

Tsui, Wing Wun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 125-137). / Abstracts in English and Chinese. / Thesis committee --- p.ii / Statement --- p.iii / Abstract --- p.iv / Chinese abstract --- p.vi / Acknowledgements --- p.viii / General abbreviations --- p.X / List of figures --- p.xiv / List of tables --- p.XV / Table of contents --- p.xvi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Literature review on LIM-homeobox genes in mouse development --- p.1 / Chapter 1.1.1 --- LIM-homeobox genes --- p.1 / Chapter 1.1.2 --- Mouse Lhx1 gene and development --- p.5 / Chapter 1.1.3 --- Mouse Lhx5 gene and development --- p.21 / Chapter 1.2 --- Mouse cerebellar Purkinje neurons --- p.26 / Chapter 1.2.1 --- Cerebellar cortex --- p.26 / Chapter 1.2.2 --- Neuronal circuitry and cerebellar functions --- p.29 / Chapter 1.2.3 --- Development of cerebellar Purkinje neurons --- p.29 / Chapter 1.2.3.1 --- Neurogenesis --- p.30 / Chapter 1.2.3.2 --- Migration and positioning --- p.30 / Chapter 1.2.3.3 --- Specification and differentiation --- p.31 / Chapter 1.2.3.4 --- Maturation --- p.31 / Chapter 1.3 --- Green Fluorescent Protein (GFP) and tau protein --- p.32 / Chapter 1.3.1 --- Introduction to tau proteins --- p.32 / Chapter 1.3.2 --- Tau-GFP fusion protein and its application in tracing neuronal projections --- p.33 / Chapter 1.4 --- Project background and aim --- p.34 / Chapter Chapter 2 --- Generation of Lhx1-tau-GFP knock-in mice --- p.38 / Chapter 2.1 --- Introduction --- p.38 / Chapter 2.2 --- Materials for molecular biological work --- p.39 / Chapter 2.2.1 --- Chemicals and kits --- p.39 / Chapter 2.2.2 --- Enzymes --- p.40 / Chapter 2.2.3 --- Plasmid vectors --- p.40 / Chapter 2.2.4 --- Oligonucleotide linkers --- p.41 / Chapter 2.2.5 --- Bacterial strains --- p.41 / Chapter 2.2.6 --- Solutions and media --- p.41 / Chapter 2.2.7 --- Radioactive isotopes and materials for autoradiography --- p.43 / Chapter 2.2.8 --- DNA probes for Southern blot hybridization --- p.43 / Chapter 2.3 --- Materials for cell culture --- p.44 / Chapter 2.3.1 --- "Chemicals, sera and others" --- p.44 / Chapter 2.3.2 --- Culture solutions and media --- p.44 / Chapter 2.3.3 --- Culture cells --- p.45 / Chapter 2.4 --- PCR primers --- p.46 / Chapter 2.5 --- Animals --- p.46 / Chapter 2.6 --- Methods for molecular biological work --- p.46 / Chapter 2.6.1 --- Preparation of plasmid DNA --- p.46 / Chapter 2.6.1.1 --- Miniprep using simple crude method --- p.47 / Chapter 2.6.1.2 --- Miniprep using purification kits --- p.48 / Chapter 2.6.1.3 --- Midiprep using purification kit --- p.50 / Chapter 2.6.2 --- Purification of specific DNA fragments --- p.51 / Chapter 2.6.2.1 --- QIAquick gel extraction kit --- p.51 / Chapter 2.6.2.2 --- QIAquick PCR purification kit --- p.52 / Chapter 2.6.3 --- Subcloning of DNA fragments --- p.53 / Chapter 2.6.3.1 --- Traditional approach based on restriction endonuclease and DNA ligase --- p.53 / Chapter 2.6.3.2 --- Preparation of subcloning inserts and vectors --- p.54 / Chapter 2.6.3.3 --- Two-way ligation of inserts and vectors --- p.55 / Chapter 2.6.4 --- Transformation of competent cells with recombinant DNA --- p.56 / Chapter 2.6.4.1 --- CaCl2 method --- p.56 / Chapter 2.6.4.2 --- Electroporation --- p.57 / Chapter 2.6.5 --- Southern hybridization --- p.59 / Chapter 2.6.5.1 --- Restriction endonuclease digestion and agarose gel electrophoresis --- p.59 / Chapter 2.6.5.2 --- Capillary transfer and fixation of DNA --- p.60 / Chapter 2.6.5.3 --- Radioactive labeling of DNA probe --- p.60 / Chapter 2.6.5.4 --- Purification of radioactive labeled probe for hybridization --- p.61 / Chapter 2.6.5.5 --- Hybridization --- p.61 / Chapter 2.6.5.6 --- Post-hybridization wash and autoradiography for signal detection --- p.62 / Chapter 2.7 --- Methods for generation and analysis of Lhx1-tau-GFP knock-in Mice --- p.63 / Chapter 2.7.1 --- Construction of targeting vector (pLhx1-tauGFP) for gene targeting of Lhx1 locus --- p.63 / Chapter 2.7.2 --- Generation of targeted embryonic stem (ES) cell clones --- p.66 / Chapter 2.7.2.1 --- Preparation of feeder cells --- p.66 / Chapter 2.7.2.2 --- Culture of ES cells on feeder layers and passage --- p.69 / Chapter 2.7.2.3 --- Harvest of cultured ES cells --- p.70 / Chapter 2.7.2.4 --- Preparation of targeting vector for transfection of ES cells --- p.71 / Chapter 2.7.2.5 --- Electroporation for transfection of ES cells --- p.71 / Chapter 2.7.2.6 --- Drug selection for targeted ES cell clones using PNS strategy --- p.72 / Chapter 2.7.2.7 --- Picking and expansion of targeted ES cell clones --- p.72 / Chapter 2.7.2.8 --- Replica plating and freezing of targeted ES cell clones --- p.74 / Chapter 2.7.2.9 --- Genomic DNA extraction from targeted ES cell clones --- p.75 / Chapter 2.7.2.10 --- Screening of homologous recombinants by Southern hybridization analysis --- p.76 / Chapter 2.7.2.11 --- Thawing and expansion of correct targeted ES cell clones --- p.76 / Chapter 2.7.2.12 --- Chromosome counting of ES cells --- p.78 / Chapter 2.7.3 --- Generation of germline chimeric mice --- p.80 / Chapter 2.7.3.1 --- Standard procedure --- p.80 / Chapter 2.7.4 --- Breeding and genotyping of mice --- p.81 / Chapter 2.7.5 --- Imaging of tau-GFP-labelled Purkinje neurons --- p.84 / Chapter 2.7.5.1 --- Animal dissection and tissue preparation --- p.84 / Chapter 2.7.5.2 --- Confocal laser scanning microscopy (CLSM) --- p.84 / Chapter 2.8 --- Results --- p.84 / Chapter 2.8.1 --- Generation of Lhx1 targeting vector (pLhx1-tauGFP) --- p.84 / Chapter 2.8.2 --- Targeted replacement of the mouse Lhx1 coding sequences by tau-GFP genetic reporter --- p.87 / Chapter 2.8.3 --- Germline transmission of Lhx1-tau-GFP allele and generation of Lhx1-tau-GFP knock-in mouse --- p.93 / Chapter 2.8.4 --- Imaging of Lhx1-tau-GFP expressing Purkinje neurons --- p.96 / Chapter 2.9 --- Discussion --- p.98 / Chapter 2.9.1 --- Tau-GFP labeling of Lhx1-expressing Purkinje neurons: implications for real-time live cell imaging --- p.98 / Chapter 2.9.2 --- Use of Lhx1-tau-GFP knock-in mice for study of Lhx1 and Lhx5 functions in Purkinje neurons survival and/or maintenance --- p.99 / Chapter Chapter 3 --- Generation of Lhx5-tau-GFP knock-in allele: alternative approach for real-time tracing of Purkinje neurons --- p.102 / Chapter 3.1 --- Introduction: Recombineering-based approach for DNA subcloning --- p.102 / Chapter 3.1.1 --- λ phage-encoded Red recombination system --- p.102 / Chapter 3.1.2 --- DNA subcloning from bacterial artificial chromosome (BAC) --- p.104 / Chapter 3.2 --- Materials for molecular biological work --- p.105 / Chapter 3.2.1 --- Chemicals and kits --- p.105 / Chapter 3.2.2 --- Enzymes --- p.105 / Chapter 3.2.3 --- Plasmid vectors and BAC DNA --- p.105 / Chapter 3.2.4 --- Bacterial strains --- p.105 / Chapter 3.2.5 --- Solutions and media --- p.106 / Chapter 3.2.6 --- PCR primers --- p.106 / Chapter 3.3 --- Methods for construction of targeting vector for mouse Lhx5 gene --- p.107 / Chapter 3.3.1 --- PCR amplification of homology sequences on BAC DNA --- p.107 / Chapter 3.3.2 --- Synthesis of retrieval arms for recombineering --- p.109 / Chapter 3.3.3 --- DNA sequencing analysis --- p.110 / Chapter 3.3.4 --- Construction of retrieval vector --- p.110 / Chapter 3.3.5 --- Preparation of electrocompetent cells for recombineering --- p.111 / Chapter 3.3.6 --- Recombineering-based retrieval of homology arms --- p.112 / Chapter 3.4 --- Results --- p.113 / Chapter 3.4.1 --- The targeting vector (pLhx5-tauGFP) for mouse Lhx5 gene --- p.113 / Chapter 3.5 --- Discussion --- p.118 / Chapter 3.5.1 --- Use of recombineering-based approach to generate targeting vector --- p.118 / Chapter 3.5.2 --- Further generation of Lhx5-tau-GFP knock-in mice --- p.119 / Chapter Chapter 4 --- Conclusion and future perspectives --- p.120 / Chapter 4.1 --- Conclusion --- p.120 / Chapter 4.2 --- Potential applications of Lhx1-tau-GFP knock-in mice for study of Lhx1 and other gene functions in cerebellum --- p.120 / Chapter 4.3 --- Potential applications of Lhx1-tau-GFP knock-in mice for study of Lhx1 -expressing cells development --- p.122 / References --- p.125

Chan, Pui Ting. / Thesis submitted in: May 2007. / On t.p. "alpha" appears as the Greek letter. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 110-118). / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgements --- p.v / Table of Contents --- p.vi / List of Abbreviations --- p.xi / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter 1.1 --- Peroxisome proliferater-activated receptors (PPARs) --- p.1 / Chapter 1.1.1 --- What are PPARs? --- p.1 / Chapter 1.1.2 --- PPAR isoforms --- p.1 / Chapter 1.1.3 --- PPARα ligands --- p.2 / Chapter 1.2 --- Biological role of PPARα --- p.3 / Chapter 1.2.1 --- Lipid metabolism --- p.3 / Chapter 1.2.2 --- Glucose metabolism --- p.5 / Chapter 1.2.3 --- Oxidative stress and carcinogenesis --- p.6 / Chapter 1.3 --- Discovery of PPARα-regulated and starvation-induced gene (PPSIG) --- p.7 / Chapter 1.4 --- Objectives of the present study --- p.9 / Chapter CHAPTER 2 --- MATERIALS AND METHODS --- p.10 / Chapter 2.1 --- Cloning of PPSIG cDNA into a pCMV-Tag epitope tagging mammalian expression vector --- p.10 / Chapter 2.1.1 --- Materials --- p.10 / Chapter 2.1.2 --- Methods --- p.10 / Chapter 2.2 --- Transient transfection of PPSIG cDNA into CHO-K1 and AML-12 cells --- p.16 / Chapter 2.2.1 --- Cell culture and transfection --- p.16 / Chapter 2.2.1.1 --- Materials --- p.16 / Chapter 2.2.1.2 --- Methods --- p.19 / Chapter 2.2.2 --- Western blot analysis --- p.20 / Chapter 2.2.2.1 --- Materials --- p.20 / Chapter 2.2.2.2 --- Methods --- p.20 / Chapter 2.3 --- Stable transfection of PPSIG cDNA into CHO-K1 and AML-12 cells --- p.22 / Chapter 2.3.1 --- Linearization of the pCMVT4B-PPSIG construct --- p.22 / Chapter 2.3.1.1 --- Materials --- p.22 / Chapter 2.3.1.2 --- Methods --- p.22 / Chapter 2.3.2 --- Cell culture and stable transfection --- p.23 / Chapter 2.3.2.1 --- Materials --- p.23 / Chapter 2.3.2.2 --- Methods --- p.23 / Chapter 2.3.3 --- Selection of the G418-resistant clones --- p.26 / Chapter 2.3.3.1 --- Materials --- p.26 / Chapter 2.3.3.2 --- Methods --- p.29 / Chapter 2.3.4 --- Picking and expanding the G418-resistant clones --- p.30 / Chapter 2.3.4.1 --- Materials --- p.30 / Chapter 2.3.4.2 --- Methods --- p.30 / Chapter 2.3.5 --- Screening and confirmation of the stable transfectants --- p.31 / Chapter 2.3.5.1 --- Reverse transcription-polymerase chain reaction (RT-PCR) --- p.31 / Chapter 2.3.5.1.1 --- Materials --- p.31 / Chapter 2.3.5.1.2 --- Methods --- p.31 / Chapter 2.3.5.2 --- Northern blot analysis --- p.35 / Chapter 2.3.5.2.1 --- Materials --- p.35 / Chapter 2.3.5.2.2 --- Methods --- p.35 / Chapter 2.3.5.3 --- Western blot analysis --- p.37 / Chapter 2.3.5.3.1 --- Materials --- p.37 / Chapter 2.3.5.3.2 --- Methods --- p.37 / Chapter 2.3.5.4 --- Immunoprecipitation --- p.37 / Chapter 2.3.5.4.1 --- Materials --- p.37 / Chapter 2.3.5.4.2 --- Methods --- p.38 / Chapter 2.3.5.5 --- Matrix-assisted laser desorption / ionization-time of flight (MALDI-TOF) mass spectrometry analysis --- p.39 / Chapter 2.3.5.5.1 --- Materials --- p.39 / Chapter 2.3.5.5.2 --- Methods --- p.39 / Chapter 2.4 --- "Analysis of the all-trans-13,14-dihydroretinol saturase (RetSat) activity by high-performance liquid chromatography (HPLC) analysis" --- p.41 / Chapter 2.4.1 --- Materials --- p.41 / Chapter 2.4.2 --- Methods --- p.42 / Chapter 2.4.2.1 --- Preparation of all-trans-retinol --- p.42 / Chapter 2.4.2.2 --- Treatment of PPSIG-transfected cells with all-trans-retinol --- p.42 / Chapter 2.4.2.3 --- Retinoid analysis --- p.43 / Chapter 2.5 --- Analysis of fatty acid compositions by gas chromatography-mass spectrometry (GC-MS) --- p.43 / Chapter 2.5.1 --- Materials --- p.43 / Chapter 2.5.2 --- Methods --- p.44 / Chapter 2.5.2.1 --- Preparation of fatty acid-BSA complex --- p.44 / Chapter 2.5.2.2 --- Treatment of PPSIG-transfected cells with fatty acid-BSA complex --- p.44 / Chapter 2.5.2.3 --- Extraction of fatty acids --- p.45 / Chapter 2.5.2.4 --- Methylation of the fatty acids --- p.45 / Chapter 2.5.2.5 --- GC-MS analysis --- p.46 / Chapter 2.5.2.6 --- Statistical analysis --- p.47 / Chapter CHAPTER 3 --- RESULTS --- p.48 / Chapter 3.1 --- The PPSIG cDNA was subcloned into a pCMV-Tag epitope tagging mammalian expression vector --- p.48 / Chapter 3.2 --- The pCMVT4B-PPSIG expression construct was transiently transfected into CHO-K1 and AML-12 cells --- p.54 / Chapter 3.3 --- Stable transfection of the pCMVT4B-PPSIG expression construct into CHO-K1 and AML-12 cells --- p.54 / Chapter 3.3.1 --- PPSIG-transfected CHO-K1 and AML-12 cells were obtained after G418 selection --- p.54 / Chapter 3.3.2 --- PPSIG-transfected CHO-K1 and AML-12 cells had high PPSIG mRNA expression --- p.58 / Chapter 3.3.3 --- PPSIG-FLAG fusion protein was over-expressed in the PPSIG- transfected CHO-K1 and AML-12 cells --- p.61 / Chapter 3.3.4 --- The stable transfectants were immunoprecipitated and identified as PPSIG protein by the mass spectrometry analysis --- p.64 / Chapter 3.4 --- PPSIG protein posseses saturase activity towards all-trans-retinol --- p.66 / Chapter 3.5 --- PPSIG protein is not a fatty acid transporter --- p.78 / Chapter CHAPTER 4 --- DISCUSSION --- p.101 / FUTURE STUDIES --- p.107 / REFERENCES --- p.110 / Appendix A: Prediction of the molecular weight of pCMVT4B- PPSIG protein --- p.119 / Appendix B: Theoretical tryptic peptides of PPSIG --- p.120 / Appendix C: Protein-peptide mass reports --- p.122 / Chapter C1. --- Peptide mass summary of trypsin-digested PPSIG immunoprecipitated protein from clone L2H4B18 --- p.122 / Chapter C2. --- Peptide mass summary of trypsin-digested PPSIG immunoprecipitated protein from clone AL2L7 --- p.123 / Appendix D: HPLC spectrum of the RetSat activity towards all- trans retinol --- p.124 / Chapter D1. --- RetSat activity towards all-trans retinol according to the Moise's group study ((Moise et al. 2004) --- p.124

<p>Transcriptional regulation largely determines which proteins and the protein levels that are found in a cell, and this is crucial in development, differentiation and responses to environmental stimuli. The major effectors of transcriptional regulation are a group of proteins known as transcription factors, which importance is supported by their frequent involvement in mendelian and complex diseases.</p><p>In paper I, we attempted to establish the importance of DNA sequence variation in transcriptional control, by analyzing the potential functionality of polymorphic short repetitive elements as cis-regulatory elements. However, the relevance of this study was constrained by the limited number of analyzed sequences and the <i>in vitro</i> nature of the experiments. To overcome these limitations, (paper II) we optimized an <i>in vivo</i> large-scale technology named ChIP-chip, which couples chromatin immunoprecipitation and microarray hybridization. We successfully identified the binding profiles of metabolic-disease associated transcription factors in 1% of the human genome, using a liver cellular model, and inferred the binding sites at base pair resolution.</p><p>Another important characteristic of transcriptional regulation is its plasticity, which allows adjusting the cellular transcriptome to cellular and environmental stimuli. In paper III, we investigated such plasticity by treating HepG2 cells with butyrate, a histone deacetylase inhibitor (HDACi) and interrogating the changes in histone H3 and H4 acetylation levels in 1% of the genome. Observation of frequent deacetylation around transcription start sites and hyperacetylation at the nuclear periphery challenges pre-assumed HDACi mechanisms of action.</p><p>Finally, in paper IV we extended the DNA binding profiles of the medically relevant transcription factors, USF1 and USF2, and H3 acetylation to the whole non-repetitive fraction of the human genome. Using motif finding tools and chromatin profiling, we uncovered the major determinants of USF-DNA interactions. Furthermore, USFs and H3ac were clearly localized around transcription start sites, frequently in the context of bidirectional promoters.</p>

Thesis (Ph. D.)--University of Hong Kong, 2005. / Title proper from title frame. Also available in printed format.

The aim of this study was to gain more information about the interactions between DNA and the histone octamer during the process of transcription. This work used a pUC8 plasmid derivative that contained the core promoter region of the RNA polymerase I of Acanthamoeba castellanii, placed upstream of four repeats of the 5S rDNA nucleosome positioning sequence from the sea urchin, Lytechinus variegatus. The plasmid was reconstituted into chromatin via addition of chicken erythrocyte histone octamers, using polyglutamic acid as a nucleosome assembly factor. The positioning of nucleosomes on the insert was monitored by restriction enzyme digestion. Proper nucleosome positioning was shown to be dependent on the presence of preassembled transcription complexes on the promoter region. The absence of preformed transcription complexes on the promoter region prior to nucleosome reconstitution perturbed the distribution of histone octamers on the repeats of the 5S rDNA. This "mispositioning" effect was related to the location of the RNA polymerase I promoter region upstream of the four repeats of the 5S rDNA fragment. Band shift assays in polyacrylamide gel electrophoresis were used to determine the relative efficiency of nucleosome formation on the promoter-containing fragment, on 5S rDNA and finally on nucleosome core particle DNA. The results indicate that the promoter fragment forms a nucleoprotein complex at lower concentration of histone than the 5S positioning sequence. This complex may not be a nucleosomal structure. The reconstituted plasmid was then used to investigate the transcriptional elongation by RNA polymerase I using the chromatin-like template containing positioned nucleosomes as compared to transcription on improperly positioned nucleosomes and on free DNA. The efficiency of transcription was related to the proper positioning of nucleosomes with regard to the tandemly repeated 208-bp 5S rDNA. The presence of phased nucleosomes in the path of the transcription complex seemed not to inhibit nor to significantly slow down the elongation as compared to free DNA. Furthermore, nucleosome positioning, as assayed by restriction endonuclease digestion, did not change after passage of the polymerase I transcription complex. / Graduation date: 1993

Transcriptional regulation largely determines which proteins and the protein levels that are found in a cell, and this is crucial in development, differentiation and responses to environmental stimuli. The major effectors of transcriptional regulation are a group of proteins known as transcription factors, which importance is supported by their frequent involvement in mendelian and complex diseases. In paper I, we attempted to establish the importance of DNA sequence variation in transcriptional control, by analyzing the potential functionality of polymorphic short repetitive elements as cis-regulatory elements. However, the relevance of this study was constrained by the limited number of analyzed sequences and the in vitro nature of the experiments. To overcome these limitations, (paper II) we optimized an in vivo large-scale technology named ChIP-chip, which couples chromatin immunoprecipitation and microarray hybridization. We successfully identified the binding profiles of metabolic-disease associated transcription factors in 1% of the human genome, using a liver cellular model, and inferred the binding sites at base pair resolution. Another important characteristic of transcriptional regulation is its plasticity, which allows adjusting the cellular transcriptome to cellular and environmental stimuli. In paper III, we investigated such plasticity by treating HepG2 cells with butyrate, a histone deacetylase inhibitor (HDACi) and interrogating the changes in histone H3 and H4 acetylation levels in 1% of the genome. Observation of frequent deacetylation around transcription start sites and hyperacetylation at the nuclear periphery challenges pre-assumed HDACi mechanisms of action. Finally, in paper IV we extended the DNA binding profiles of the medically relevant transcription factors, USF1 and USF2, and H3 acetylation to the whole non-repetitive fraction of the human genome. Using motif finding tools and chromatin profiling, we uncovered the major determinants of USF-DNA interactions. Furthermore, USFs and H3ac were clearly localized around transcription start sites, frequently in the context of bidirectional promoters.