Thesis (Ph. D.)--University of Chicago, Dept. of New Testament and Early Christian Literature, June 1999. / Includes bibliographical references. Also available on the Internet.

Thesis (MBA)--North-West University, Potchefstroom Campus, 2008.

Thesis (MBA)--North-West University, Potchefstroom Campus, 2008.

Thesis (MBA)--North-West University, Potchefstroom Campus, 2008.

No description available.

Epithelial sheets line the surfaces of the body, forming a barrier between the external environment and internal tissues. During development, regulation of epithelial architechture can drive morphogenesis and build the three-dimensional structures of the body. Epithelial form and function derive from the polarized morphology of epithelial cells, which have apical surfaces that face the external environment, lateral surfaces containing cell-cell junctions and basal surfaces that connect to the underlying tissue. A network of polarity proteins establishes the apico-basolateral axis, while a system of polarized membrane traffic ensures delivery of specialized cargo to distinct membrane surfaces. How these systems of polarity and trafficking are integrated is still poorly understood. The focus of my study was to investigate how the apical polarity proteins Cdc42, Par6, Bazooka and aPKC (the “Par complex”) regulate polarity and adherens junction (AJ) integrity during Drosophila development. Upon perturbation of Cdc42/Par activity during embryogenesis, apical membrane proteins accumulate in sorting endosomes. This trafficking defect occurs throughout the ectoderm, but in the ventral neuroectoderm (VNE) is accompanied by a concomitant depletion of the apical proteins from the plasma membrane (PM) and a loss of AJ integrity. I have demonstrated that the VNE phenotype is a consequence of the relatively high morphogenetic activity of this tissue. Furthermore, I have shown that the AJ defects are likely a downstream consequence of the depletion of important apical polarity factors, such as Crumbs, from the PM. To further characterize the mechanism of apical trafficking, I searched for interactors of Cdc42/Par in the membrane trafficking machinery. I describe interactions between several trafficking genes and Cdc42/Par and provide evidence that Vps26, a component of the retromer complex that retrieves proteins from endosomal membrane and delivers them to the Golgi for re-secretion, is phosphorylated by aPKC and acts as an aPKC effector in the recycling of apical membrane proteins. I propose that Cdc42/Par regulate the retromer to promote the PM localization of apical proteins, which is important to maintain AJ integrity in morphogenetically active tissues.

Thesis (Ph. D.)--University of Virginia, 2006. / Includes bibliographical references. Also available online through Digital Dissertations.

In the budding yeast Saccharomyces cerevisiae, the G1-specific cyclin-dependent kinases (Cdks) Cln1-, Cln2-Cdc28 and Pcl1-, Pcl2-Pho85 are essential for ensuring that DNA replication and cell division are properly linked to cell polarity and bud morphogenesis. However, like most genes in S. cerevisiae, individual cyclin genes are not required for viability, and the phenotypes associated with deletion of any single cyclin gene tend to be subtle. My goal was to dissect the cellular roles of the G1 cyclins by systematically identifying their genetic interactions. To do this, I conducted Synthetic Genetic Array (SGA) screens using strains deleted for different combinations of cyclin genes. The results of screens with strains deleted for the G1 cyclin pairs, CLN1, CLN2, or PCL1, PCL2, confirmed a role for these cyclins in cell polarity regulation and identified novel G1 Cdk substrates, which I examined in more detail. One cell polarity regulator that showed an interesting pattern of genetic interactions with G1 cyclins was BNI1, which encodes a yeast formin protein. Overexpression of BNI1 caused an Synthetic Dosage Lethal interaction in the absence of both G1 cyclin pairs while its deletion caused synthetic lethality specifically in the absence of PCL1, PCL2. Consistent with these genetic interactions, phosphorylation of Bni1 was partially dependent on CLN1, CLN2. It has been proposed that Bni1 is regulated by intramolecular interactions. In an effort to discover how phosphorylation might affect Bni1 function, I developed assays to test for intramolecular interactions. In my experiments I found no evidence that Bni1 is regulated by intramolecular binding, as was proposed from parallels with its mouse homolog mDia1. I also found that deletion of BNI4, which encodes an adaptor protein that targets several proteins to the bud neck, results in severe growth defects in the absence of the Cdc28 cyclins Cln1 and Cln2, and overexpression of BNI4 was toxic in yeast cells lacking the Pho85 cyclins Pcl1 and Pcl2. I discovered that Bni4 was phosphorylated by Pcl1- and Pcl2-Pho85 in vitro and that phosphorylation of Bni4 was dependent on PCL1 and PCL2 in vivo. Further analysis showed that phosphorylation of Bni4 by Pcl-Pho85 is necessary for its localization to bud neck, and the bud neck structure can be disrupted by overexpressing BNI4 in pcl1pcl2 mutant cells. I propose that if Bni4 cannot be regulated by phosphorylation, it may titrate away an essential component that resides at the bud neck, thus causing catastrophic morphogenesis defects. The relationship between G1 Cdk activity and the polarity regulator Bni4 serves as a bridge to link the cell cycle machine to the regulation of cell.

In the budding yeast Saccharomyces cerevisiae, the G1-specific cyclin-dependent kinases (Cdks) Cln1-, Cln2-Cdc28 and Pcl1-, Pcl2-Pho85 are essential for ensuring that DNA replication and cell division are properly linked to cell polarity and bud morphogenesis. However, like most genes in S. cerevisiae, individual cyclin genes are not required for viability, and the phenotypes associated with deletion of any single cyclin gene tend to be subtle. My goal was to dissect the cellular roles of the G1 cyclins by systematically identifying their genetic interactions. To do this, I conducted Synthetic Genetic Array (SGA) screens using strains deleted for different combinations of cyclin genes. The results of screens with strains deleted for the G1 cyclin pairs, CLN1, CLN2, or PCL1, PCL2, confirmed a role for these cyclins in cell polarity regulation and identified novel G1 Cdk substrates, which I examined in more detail. One cell polarity regulator that showed an interesting pattern of genetic interactions with G1 cyclins was BNI1, which encodes a yeast formin protein. Overexpression of BNI1 caused an Synthetic Dosage Lethal interaction in the absence of both G1 cyclin pairs while its deletion caused synthetic lethality specifically in the absence of PCL1, PCL2. Consistent with these genetic interactions, phosphorylation of Bni1 was partially dependent on CLN1, CLN2. It has been proposed that Bni1 is regulated by intramolecular interactions. In an effort to discover how phosphorylation might affect Bni1 function, I developed assays to test for intramolecular interactions. In my experiments I found no evidence that Bni1 is regulated by intramolecular binding, as was proposed from parallels with its mouse homolog mDia1. I also found that deletion of BNI4, which encodes an adaptor protein that targets several proteins to the bud neck, results in severe growth defects in the absence of the Cdc28 cyclins Cln1 and Cln2, and overexpression of BNI4 was toxic in yeast cells lacking the Pho85 cyclins Pcl1 and Pcl2. I discovered that Bni4 was phosphorylated by Pcl1- and Pcl2-Pho85 in vitro and that phosphorylation of Bni4 was dependent on PCL1 and PCL2 in vivo. Further analysis showed that phosphorylation of Bni4 by Pcl-Pho85 is necessary for its localization to bud neck, and the bud neck structure can be disrupted by overexpressing BNI4 in pcl1pcl2 mutant cells. I propose that if Bni4 cannot be regulated by phosphorylation, it may titrate away an essential component that resides at the bud neck, thus causing catastrophic morphogenesis defects. The relationship between G1 Cdk activity and the polarity regulator Bni4 serves as a bridge to link the cell cycle machine to the regulation of cell.

This work is concerned with the automatic understanding of evaluative text. We investigate sentence level opinion polarity prediction by assigning lexical polarities and deriving sentence polarity from these with the use of contextual valence shifters. A methodology for iterative failure analysis is developed and used to refine our lexicon and identify new contextual shifters. Algorithms are presented that employ these new shifters to improve sentence polarity prediction accuracy beyond that of a state-of-the-art existing algorithm in the domain of consumer product reviews. We then apply the best configuration of our algorithm to the domain of movie reviews.