Dans les organites des plantes, l’édition de l’ARN consiste majoritairement en une désamination de cytidines à des sites spécifiques de l’ARNm. Trente-quatre sites d’édition ont été découverts dans les transcrits chloroplastiques d’Arabidopsis thaliana et plus de 500 dans les transcrits mitochondriaux. Depuis 2005, beaucoup de facteurs d’édition ont été trouvés. La majorité de ces protéines appartiennent à la famille des «PentatricoPeptide Repeat» (PPR). Parmi ces PPR, certaines contiennent un domaine DYW possédant de faibles similarités avec les cytidines désaminases (CDA), alors que d’autres en sont dénuées, générant un doute sur le fait qu’il ait une activité CDA. Le gène At1g47580 (DYW1) code une protéine unique chez Arabidopsis thaliana contenant «seulement» un domaine DYW. Il a été proposé que DYW1 puisse interagir avec les PPR ne contenant pas de domaine DYW, pour former un hétérodimère, capable d’éditer spécifiquement un site. En accord avec cette hypothèse, nous avons montré que DYW1 agissait sur le même site d’édition que CRR4, une PPR sans domaine DYW, et que ces protéines interagissaient in vivo. De plus, nous avons montré que DYW1 remplaçait les parties manquantes de CRR4 pour l’édition. Pour obtenir plus d’informations sur la fonction du domaine DYW, des mutations ont été introduites dans DYW1. Nous avons montré que la signature CDA dans les protéines DYW était essentielle à l’édition de l’ARN ainsi qu’à l’interaction avec les ions zinc. Les données sont en accord avec l’hypothèse d’une activité CDA dans le domaine DYW. Cependant, aucune activité CDA n’a pu être mise à jour in vitro. Il est vraisemblable qu’au moins un cofacteur doive encore être identifié. / In plant organelles, RNA editing mostly takes the form of conversions of cytidines to uridines at specific sites in mRNAs. Thirty-four editing sites have been found in Arabidopsis thaliana chloroplast transcripts and more than 500 sites in mitochondrial transcripts. Since 2005, lots of proteins have been found to act as RNA editing factors. Most of these proteins belong to the PentatricoPeptide Repeat (PPR) family. Amongst these PPR, some contain a DYW domain with weak similarity to cytidine deaminases (CDA), whilst others lack such a domain, creating doubts about whether this domain is required for editing. The gene At1g47580 (named DYW1) encodes a protein in Arabidopsis thaliana that contains “only” a DYW domain. Our initial hypothesis was that DYW1 might interact with PPR proteins that lack a DYW domain, in order to form a heterodimer, able to perform site-specific editing. In accordance with this hypothesis, we discovered that DYW1 is involved in editing the same site as CRR4, a PPR lacking a DYW domain, and that these two proteins interact together in vivo. Moreover, we showed that DYW1 replaces all the missing parts of CRR4 for editing. So, other partners need to be hypothesized for other DYW-lacking editing factors if this hypothesis is to be generalized. The highly conserved residues making up the CDA signature in DYW proteins were found to be essential for RNA editing and are also required for zinc binding, which is a known characteristic of CDAs. All the data so far are consistent with the DYW domain being (part of) a CDA activity; nevertheless, no CDA activity could be detected in vitro. It is likely that at least one required cofactor remains to be identified.

Friedreich ataxia (FRDA) is a neurodegenerative disorder that is inherited in an autosomal recessive pattern. The most common FRDA mutation is hyperexpansion of a GAA triplet repeat sequence in the first intron of the affected gene, frataxin (FXN), resulting in decreased frataxin protein expression. The hyperexpanded GAA repeats can adopt unusual DNA structures and induce aberrant epigenetic changes leading to heterochromatin mediated gene silencing. Several epigenetic changes, including increased levels of DNA methylation, histone modifications, repressive chromatin formation and elevated levels of non-coding RNA have been reported in FRDA. It has been reported that a novel FXN antisense transcript (FAST-1), is present at higher levels in FRDA patient-derived fibroblasts and its overexpression is associated with the depletion of CTCF, a chromatin insulator protein, and heterochromatin formation involving the critical +1 nucleosome. Previously, characteristics of FAST-1 were investigated in our lab and a full-length FAST-1 transcript containing a poly (A) tail was identified. To investigate any possible effects of FAST-1 on FXN expression, I first overexpressed this FAST-1 transcript in three different non-FRDA cell lines and a consistent decrease of FXN expression was observed in each cell type compared to control cells. I also identified that FAST-1 copy number is positively correlated with increased FAST-1 expression, which in turn is negatively correlated with FXN expression in FAST-1 overexpressing cells. Additionally, we found that FAST-1 overexpression is associated with increased levels of DNA methylation at CpG sites U6 and U11 of the FXN upstream GAA repeat region, together with CTCF depletion and heterochromatin formation at the 5'UTR of the FXN gene. To further investigate the role of FAST-1 in FXN gene silencing, I used a small hairpin RNA (shRNA) strategy to knock down FAST-1 expression in FRDA fibroblast cells. I found that knocking down FAST-1 increases FXN expression, but not to the level of control cells. Lastly, I investigated the pattern of FAST-1 expression and histone modifications at the FXN transgene in our new FRDA mouse model, designated YG8LR. The YG8LR mice showed decreased levels of FXN expression and H3K9ac and increased levels of FAST-1 expression and H3K9me3. Our data suggest that since FAST-1 is associated with FXN gene silencing, inhibition of FAST-1 may be an approach for FRDA therapy.

Polyglutamine (polyQ) diseases are progressive fatal neurodegenerative movement disorders. Although many cellular processes are perturbed in polyQ disease, recent studies highlight the importance of protein misfolding as a central event in polyQ toxicity. Spinocerebellar ataxia type 3 (SCA3), also known as Machado-Joseph disease, is a particularly interesting polyQ disease because of the special qualities of the disease protein ataxin-3, which normally participates in cellular protein quality control. Here I use multiple mouse models of disease to explore toxic protein species and the role of protein homeostasis in SCA3 pathogenesis. In Chapter 1, I review the key features of polyQ disease, and outline the background and rationale behind our strategy for identifying toxic protein species in SCA3. In Chapter 2, I examine the role of the protein quality control ubiquitin ligase, CHIP (C-terminus of Hsp70 interacting protein), in regulating the toxicity of expanded ataxin-3 in vivo. Genetic reduction or removal of CHIP increases formation of detergent-resistant ataxin-3 microaggregates specifically in the brain. Concomitant with this, reduction or removal of CHIP exacerbates the phenotype of SCA3 mice, revealing a correlation between high levels of microaggregates and phenotypic severity. Additional cell-based studies confirm that CHIP may not directly mediate ataxin-3 degradation, suggesting that CHIP reduces expanded ataxin-3 toxicity in the brain primarily by enhancing ataxin-3 solubility. In Chapter 3, I use various biochemical techniques to reveal the presence of brain-specific ataxin-3 microaggregates in two genetically distinct mouse models of SCA3. Selective neuropathological evaluation of SCA3 mice reveals that major neuronal loss and reactive glial proliferation are not shared features of phenotypically-manifesting SCA3 mice. Additional studies fail to provide evidence for loss-of-function of endogenous ataxin-3 in SCA3 mice. Our results suggest that neuronal dysfunction in SCA3 is mediated through a toxic gain-of-function mechanism by ataxin-3 microaggregates in the CNS. In Chapter 4, I discuss important areas for future research in polyQ disease. I describe studies that would help elucidate the structural nature of toxic soluble microaggregates, and their effects on other cellular proteins. I also consider how the results described in this thesis inform potential treatment strategies.

The ability to attract and retain customers through providing excellent service quality is a necessity for any business in every field. However, before a firm can expect to consistently provide high quality service, it must first know how to measure and identify areas of needed improvement. While service quality research has been conducted in most of the major sectors of the economy, the residential real estate brokerage industry is only beginning to incorporate existing knowledge of service quality management. This is especially disconcerting given that real estate is such a large part of local and national economies around the world. The purpose of this thesis is to identify the best instrument that can be used to measure service quality in the residential real estate brokerage industry. The findings reveal that the reliability, responsiveness and empathy dimensions significantly lead to increases in the overall evaluation of service the firm provides. The empathy dimension also significantly causes homebuyers to recommend the firm to others. Additionally, empathy significantly causes the client to use the firm again. Finally, as hypothesized, overall satisfaction leads to both repeat uses of the firm and recommending the firm to a friend. / Doctor of Philosophy (PhD)

<p>The fashion industry is one of the most exciting and fast-moving industries in the worldand the companies within the fashion industry are driven by the reputation of their brand.(Hines and Bruce, 2001) Some celebrities and athletes use their names as a label so that the wearer associates the clothes with the person, and therefore that brand takes on the image of the celebrity. This research is concentrated on the customers of a particular fashion company, Björn Borg. In the fashion industry, it is not only important who is wearing the brand, but also who is not wearing the brand, which leads to the aim of this paper: Can a company sacrifice its brand image if it holds on to all of its customers,including those outside of its target market? From our research, we were able to draw the following conclusions: The customers within the target group associate the brand with some of the characteristics of customers outside the target group and, thus, the image of Björn Borg is slightly different from what the company would like their image to be. Our analysis reveals that there are many who associate the brand with older people. In a way, the older customers may influence the younger ones into thinking the brand is for an older age group. Also, many associate the brand with the “average joe” and with the tennis player despite the efforts of the company to create a special brand, not average, that stands apart from the tennis player, Björn Borg. Therefore, our study indicates that a company can sacrifice brand image if it holds on to all customers including those outside their target market.</p>

The fashion industry is one of the most exciting and fast-moving industries in the worldand the companies within the fashion industry are driven by the reputation of their brand.(Hines and Bruce, 2001) Some celebrities and athletes use their names as a label so that the wearer associates the clothes with the person, and therefore that brand takes on the image of the celebrity. This research is concentrated on the customers of a particular fashion company, Björn Borg. In the fashion industry, it is not only important who is wearing the brand, but also who is not wearing the brand, which leads to the aim of this paper: Can a company sacrifice its brand image if it holds on to all of its customers,including those outside of its target market? From our research, we were able to draw the following conclusions: The customers within the target group associate the brand with some of the characteristics of customers outside the target group and, thus, the image of Björn Borg is slightly different from what the company would like their image to be. Our analysis reveals that there are many who associate the brand with older people. In a way, the older customers may influence the younger ones into thinking the brand is for an older age group. Also, many associate the brand with the “average joe” and with the tennis player despite the efforts of the company to create a special brand, not average, that stands apart from the tennis player, Björn Borg. Therefore, our study indicates that a company can sacrifice brand image if it holds on to all customers including those outside their target market.

Background: Long terminal repeats (LTRs, consisting of U3-R-U5 portions) are important elements of retroviruses and related retrotransposons. They are difficult to analyse due to their variability. The aim was to obtain a more comprehensive view of structure, diversity and phylogeny of LTRs than hitherto possible. Results: Hidden Markov models (HMM) were created for 11 clades of LTRs belonging to Retroviridae (class III retroviruses), animal Metaviridae (Gypsy/Ty3) elements and plant Pseudoviridae (Copia/Ty1) elements, complementing our work with Orthoretrovirus HMMs. The great variation in LTR length of plant Metaviridae and the few divergent animal Pseudoviridae prevented building HMMs from both of these groups. Animal Metaviridae LTRs had the same conserved motifs as retroviral LTRs, confirming that the two groups are closely related. The conserved motifs were the short inverted repeats (SIRs), integrase recognition signals (5' TGTTRNR ... YNYAACA 3'); the polyadenylation signal or AATAAA motif; a GT-rich stretch downstream of the polyadenylation signal; and a less conserved AT-rich stretch corresponding to the core promoter element, the TATA box. Plant Pseudoviridae LTRs differed slightly in having a conserved TATA-box, TATATA, but no conserved polyadenylation signal, plus a much shorter R region. The sensitivity of the HMMs for detection in genomic sequences was around 50% for most models, at a relatively high specificity, suitable for genome screening. The HMMs yielded consensus sequences, which were aligned by creating an HMM model (a 'Superviterbi' alignment). This yielded a phylogenetic tree that was compared with a Pol-based tree. Both LTR and Pol trees supported monophyly of retroviruses. In both, Pseudoviridae was ancestral to all other LTR retrotransposons. However, the LTR trees showed the chromovirus portion of Metaviridae clustering together with Pseudoviridae, dividing Metaviridae into two portions with distinct phylogeny. Conclusion: The HMMs clearly demonstrated a unitary conserved structure of LTRs, supporting that they arose once during evolution. We attempted to follow the evolution of LTRs by tracing their functional foundations, that is, acquisition of RNAse H, a combined promoter/polyadenylation site, integrase, hairpin priming and the primer binding site (PBS). Available information did not support a simple evolutionary chain of events.

By 2006, the U.S. government has spent $15 billion to address the degradation of urban streams, including erosion of stream banks, disconnection of rivers from the floodplain, and disturbance of surface runoff pathways. Bank stabilization is one of the most prevalent restoration activities in urban stream restoration. Unfortunately, most stream restoration projects have been undertaken without a pre- or post-evaluation of the impact of stream restoration on real value in the area. All restoration projects beg the question: Did the money spent on the project result in greater benefits to stream stability as well as to adjacent properties? The Walnut Creek watershed, located in Austin, Texas, has experienced varying stages of urbanization since the 1990s. One of the streams, the Walnut Creek tributary, was restored in 2003. The purpose of this study is to assess the impact of stream restoration on housing values. We applied the hedonic pricing method to evaluate the changes in housing value associated with housing and environmental characteristics. Repeat ground photography was utilized to assess stream restoration activities at spatial and temporal scales. Our results suggest that the stream restoration project resulted in significant positive impacts on housing values in the periods of restoration (8.3%) and restoration adjustment (10.7%). However, the project did not enhance the values of houses on the floodplain. In addition, results show that erosion had continuous negative impacts on housing values. Overall, the restoration project contributed to the greater benefits during the restoration adjustment period right after restoration by an increase of 1% of the average housing value for each property on the restoration site. In this study, the benefits of stream restoration project were minimal since bank stabilization was the main activity considered in this stream restoration project. Nevertheless, restoration enhances the stability of the stream banks, minimizes erosion problems, and presents an enhanced aesthetic beauty of the stream in Austin, Texas.

Transmit diversity usually employs multiple antennas at the transmitter. However, many wireless devices such as mobile cellphones, Personal Digital Assistants (PDAs), just to name a few, are limited by size, hardware complexity, power and other constraints to just one antenna. A new paradigm called cooperative communication which allows single antenna mobiles in a multi-user scenario to share their antennas has been proposed lately. This multi-user configuration generates a virtual Multiple-Input Multiple-Output system, leading to transmit diversity. The basic approach to cooperation is for two single-antenna users to use each other's antenna as a relay in which each of the users achieves diversity. Previous cooperative signaling methods encompass diverse forms of repetition of the data transmitted by the partner to the destination. A new scheme called coded cooperation [15] which integrates user cooperation with channel coding has also been proposed. This method maintains the same code rate, bandwidth and transmit power as a similar non-cooperative system, but performs much better than previous signaling methods [13], [14] under various inter-user channel qualities. This dissertation first discusses the coded cooperation framework that has been proposed lately [19], coded cooperation with Repeat Convolutional Punctured Codes (RCPC) codes and then investigates the application of turbo codes in coded cooperation. In this dissertation we propose two new cooperative diversity schemes which are the Repeat-Punctured Turbo Coded cooperation and coded cooperation using a Modified Repeat-Punctured Turbo Codes. Prior to that, Repeat-Punctured Turbo codes are introduced. We characterize the performance of the two new schemes by developing the analytical bounds for bit error rate, which is confirmed by computer simulations. Finally, the turbo coded cooperation using the Forced Symbol Method (FSM) is presented and validated through computer simulations under various inter-user Signal-to-Noise Ratios (SNRs). / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2008.

The luteinizing hormone receptor (LHR) belongs to the G protein-coupled receptorfamily. It consists of two distinct domains; the N-terminal extracellular exodomain and themembrane associated endodomain which includes 7 transmembrane domains, 3 exoloops, 3cytoloops and a C-terminal tail. Sequence alignment and computer modeling suggest thepresence of Leu Rich Repeat (LRR) motifs in the exodomain. Although their structuralsimilarity is high, each LRR is not equally important for hormone binding. Ala-scanning andtruncation studies performed in our laboratory suggest that LRR2 and LRR4 appear to be themost crucial. The Ala-scanning data suggest that Leu103 and Ile105 in LRR4 are important forhormone binding. However, it is not clear whether these two residues make direct contact withhuman chorionic gonadotropin (hCG) or if they are necessary for the overall structural integrityof LRR4. In this work, the LHR peptide mimics of LRR4 were used for photoaffinity labeling todetermine whether Leu103 and Ile105 directly interact with hormone. Furthermore, LRR4peptides containing the photoactivable benzoylphenylalanine (Bpa) were used to determinewhether the LRR structure really exists in the LHR exodomain, whether LRR 4 interact withhCG, and which residues of LRR4 interact with hCG. Bpa was directly incorporated intodifferent positions of the LRR4 peptide sequence to examine the labeling ability of individualamino acids. The results suggest that LRR4, in particular the sequence of Lys101-Cys106,makes direct contact with hCG. However Leu103 and Ile105 do not interact with hCG but mayform the hydrophobic core of the LRR4 loop, which appears to be crucial for the LRR structure.Existing data suggest that glycoprotein hormones initially bind the exodomain. Thehormone/exodomain complex undergoes conformational adjustments and stimulates theendodomain of the receptor to generate hormone signals. The exoloops modulate hormonebinding and signaling; however, little is known about whether the hormone/exodomain complexcontacts the endodomain. To address this issue, we investigated whether the exoloops interactwith the hormone. First, we examined exoloop 3 that connects transmembrane domains 6 and 7which are important for signal generation. We present the first physical evidence that LHRexoloop 3 interacts with hCG.