Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2002. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Biochemistry." Includes bibliographical references (p. 124-146).

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 109-119).

Comparative study of homologous structures in closely related species allows the identification of changes in gene regulatory mechanisms and their impact on the evolution of developmental processes. Nematodes, the invertebrate roundworms, are well suited for such studies, especially the Caenorhabditis briggsae and its famous cousin C. elegans. These two worms diverged from a common ancestor roughly 30 million years ago, yet appear morphologically almost identical. My Ph.D. thesis has focused on a set of nuclear factors in C. briggsae that negatively regulate cell proliferation to generate the hermaphrodite-specific mating and egg-laying organ, i.e., vulva. To this end, I have taken a two-pronged approach: one, developing resources to facilitate genetic and genomic studies in this species, and two, characterizing the roles of a novel class of genes and known repressors of vulval development. My work has uncovered substantial differences in the underlying genetic networks that regulate vulva formation in C. briggsae and C. elegans. / Thesis / Candidate in Philosophy

AgaR, a protein in <i>Escherichia coli</i> thought to control the metabolism of N-acetylgalactosamine, is a member of the DeoR family of transcriptional regulators. Three transcriptional promoters within a cluster of genes containing the gene for AgaR were identified, specific for <i>agaR, agaZ</i> and <i>agaS</i>, and the transcription start sites mapped. Transcription from these promoters was specifically induced by N-acetylgalactosamine or galactosamine, though K-12 strains lacked the ability to utilize these as sole sources of carbon. The activity of these promoters was constitutively elevated in a strain in which <i>agaR</i> had been disrupted confirming that the promoters are subject to negative regulation by AgaR. AgaR-His6, purified using immobilized metal affinity chromatography, was used for DNase I footprint analysis of the promoter regions. Four operator sites bound by AgaR were identified. A putative consensus binding sequence for AgaR was proposed based on these four sites. <i>In vivo</i> and <i>in vitro</i> analysis of the <i>agaZ</i> promoter indicated that this promoter was activated by the cAMP-cAMP receptor protein (CRP). Expression from the <i>aga</i> promoters was less sensitive to catabolite repression in revertants capable of <i>N</i>-acetylgalactosamine utilization, suggesting that these revertants have mutation(s) that result in an elevated level of inducer for AgaR. A cluster of genes at minute 87.7 of the <i>E. coli</i> genome contains a gene that encodes another member of the DeoR family of transcriptional regulators. This protein, YihW, is more similar to GlpR, transcriptional regulator of <i>sn</i>-glycerol 3-phosphate metabolism in <i>E. coli</i>, than other members of the DeoR family. Despite the high degree of similarity, YihW lacked the ability to repress P_glpK, a promoter known to be controlled by GlpR. A variant of YihW containing substitutions in the putative recognition helix to more closely match the recognition helix of GlpR was also unable to repress P_glpK. Transcriptional promoters identified in this cluster of genes were negatively regulated by YihW. Regulation of genes involved in the metabolism of <i>sn</i>-glycerol 3-phosphate in <i>E. coli</i> by GlpR has been well characterized. However, the function of a protein (GlpE) encoded by a gene cotranscribed with that for GlpR was unknown prior to this work. GlpE was identified as a single-domain, 12-kDa rhodanese (thiosulfate:cyanide sulfurtransferase). The enzyme was purified to near homogeneity and characterized. As shown for other characterized rhodaneses, kinetic analysis revealed that catalysis occurs via an enzyme-sulfur intermediate utilizing a double-displacement mechanism requiring an active-site cysteine. K_m (SSO₃²⁻) and K_m (CN⁻) were determined to be 78 mM and 17 mM, respectively. The native molecular mass of GlpE was 22.5 kDa indicating that GlpE functions as a dimer. GlpE exhibited a kcat of 230 s-1. Thioredoxin, a small multifunctional dithiol protein, served as sulfur-acceptor substrate for GlpE with an apparent K_m of 34 mM when thiosulfate was near its K_m, suggesting thioredoxin may be a physiological substrate. / Ph. D.

Zhang, Bin. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 154-187). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Li, Chi Han Samson. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 158-175). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

The helix-loop-helix (HLH) family of transcription regulatory proteins are fundamental regulators in the processes of cell proliferation and differentiation, cell lineage determination, myogenesis, neurogenesis, and sex determination in a wide range of multicellular organisms. A gene encoding a novel class II HLH protein has recently been identified from a human B-cell eDNA library using a yeast two-hybrid screen. The predicted human ABF -1 polypeptide sequence was used to search the Caenorhabditis elegans genome database for a C. elegans ABF-1 homolog. This bHLH protein, called C. elegans ABF -1 (CeABF -1 ), has a bHLH domain that shares 72% amino acid similarity with its human ABF-1 relative. The expression of the CeABF-1 mRNA has been detected in larval stages L2, L3, L4, and adult, however the mRNA is most highly expressed at the L3 and L4 stages. CeABF -1 protein is capable of heterodimerizing with the human E2A gene product, E4 7. Like human ABF -1, CeABF -1 expression in the presence of the E4 7 protein results in a reduction in E2A mediated gene activation. It has therefore been concluded that CeABF -1 , like human ABF -1 , also acts as a transcriptional repressor. Because C. elegans shares many conserved genes with higher eukaryotic organisms it has become a model organism for in depth genetic studies. It has therefore become increasingly desirable to investigate the possibility of alternative protein-protein interactions that can potentially occur within C. elegans, so it was necessary to construct a C. elegans eDNA library along with the appropriate bait vector expressing the CeABF- 1 protein. The titer ofthe primary library was calculated to be 9.7 x I06 clones, 10-fold greater than minimum titer requirement of I x I 06 clones for a good representational library. Sequencing of the CeABF -I insert confirmed successful construction of a mutation-free bait construct suitable for use in yeast two-hybrid screening. Yeast-two hybrid analysis revealed two new interactors, one of which was identified as an aldose reductase homolog, while the other remains uncharacterized.

Thesis (Ph. D.)--University of Missouri--Columbia, 2002. / Typescript. Vita. Includes bibliographical references (leaves 179-198). Also issued on the Internet.