Thesis (Ph.D.)--University of Delaware, 2005. / Principal faculty advisor: Babatunde Ogunnaike, Dept. of Chemical Engineering. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, Dept. of Ecology and Evolution, August 2001. / Includes bibliographical references. Also available on the Internet.

Thesis (Honors)--College of William and Mary, 2009. / Includes bibliographical references (leaves 67-73). Also available via the World Wide Web.

The oncogenic protein BCL-3, a member of the IκB family, was originally identified in a subset of human B-cell chronic lymphocytic leukemias that carry a translocation t(14,19), which results in BCL-3 overexpression. BCL-3 is also overexpressed in many solid tumors, such as in breast cancers and in cylindromas. This IκB protein activates or represses gene transcription through binding with the NF-κB proteins p50 and p52. Furthermore, BCL-3 is K63-linked polyubiquitinated, which leads to its translocation into the nucleus and to its target genes expression. BCL-3 is also K48-linked polyubiquitinated after GSK3 phosphorylation, which leads to its subsequent proteasomal degradation. However, the mechanisms underlying both its polyubiquitination and its ability to repress gene transcription remain poorly understood. In order to gain more insight into these BCL-3 functions, parallel screenings involving both yeast-two-hybrid experiments and biochemical purifications led to the identification of BCL-3-interacting partners. Those screenings identified CtBP as a molecule required for the ability of BCL-3 to repress gene transcription. CtBP is also required for the stability, for the oncogenic potential and for the ability of BCL-3 to inhibit UV-mediated cell apoptosis in keratinocytes. We also defined the E3 ligase TBLR1 as a key element involved in BCL-3 polyubiquitination and degradation through a GSK3-independent pathway and the proteasome subunit PSMB1 as a protein required for the GSK3-dependent and -independent proteasomal degradation of polyubiquitinated BCL-3. Importantly, all interactions require unique motifs within the amino-terminal domain of BCL-3. In conclusion, our data define multiple BCL-3-associated proteins that differentially and specifically regulate its function and stability and indicate that a better understanding of the mechanisms underlying the oncogenic properties of this IκB protein could be achieved through similar interactomic studies.

Little is known about dosage compensation in autosomal genes. Transcription-level compensation of deletions and other loss-of-function mutations may be a mechanism of dominance of wild-type alleles, a ubiquitous phenomenon whose nature has been a subject of a long debate. We measured gene expression in two isogenic Drosophila lines heterozygous for long deletions and compared our results with previously published gene expression data in a line heterozygous for a long duplication. We find that a majority of genes are at least partially compensated at transcription, both for 1/2-fold dosage (in heterozygotes for deletions) and for 1.5-fold dosage (in heterozygotes for a duplication). The degree of compensation does not vary among functional classes of genes. Compensation for deletions is stronger for highly expressed genes. In contrast, the degree of compensation for duplications is stronger for weakly expressed genes. Thus, partial transcriptional compensation appears to be based on regulatory mechanisms that insure high transcription levels of some genes and low transcription levels of other genes, instead of precise maintenance of a particular homeostatic expression level. Given the ubiquity of transcriptional compensation, dominance of wild-type alleles may be at least partially caused by of the regulation at transcription level.

During tissues development multipotent progenitor cells establish tissue-specific gene expression programmes, leading to differentiation into specialized cell types. It has been previously shown that the transcription factor p63, a master regulator of skin development, controls the expression of adhesion molecules and essential cytoskeleton components. It has also been shown that p63 plays an important role in establishing distinct three-dimensional conformations in the Epidermal Differentiation Complex (EDC) locus (Fessing et al., 2011). Here we show that in p63-null mice about 32% of keratinocytes showed altered nuclear morphology. Alterations in the nuclear shape were accompanied by decreased expression of nuclear lamins (Lamin A/C and Lamin B1), proteins of the LINC complex (Sun-1, nesprin-2/3) and Plectin. Plectin links components of the nuclear envelope (nesprin-3) with cytoskeleton and ChIP-qPCR assay with adult epidermal keratinocytes showed p63 binding to the consensus binding sequences on Plectin 1c, Sun-1 and Nesprin-3 promoters. As a possible consequence of the altered expression of nuclear lamins and nuclear envelope-associated proteins, changes in heterochromatin distribution as well as decrease of the expression of several polycomb proteins (Ezh2, Ring1B, Cbx4) has been observed in p63-null keratinocytes. Moreover, recent data in our lab have showed that p63 directly regulates Cbx4, a component of the polycomb PRC1 complex. Here we show that mice lacking Cbx4 displayed a skin phenotype, which partially resembles the one observed in p63-null mice with reduced epidermal thickness and keratinocyte proliferation. All together these data demonstrate that p63-regulated gene expression program in epidermal keratinocytes includes not only genes encoding adhesion molecules, cytoskeleton proteins (cytokeratins) and chromatin remodelling factors (Satb1, Brg1), but also polycomb proteins and components of the nuclear envelope, suggesting the existence of a functional link between cytoskeleton, nuclear architecture and three dimensional nuclear organization. Other proteins important for proper epidermal development and stratification, are cytokeratins. Here, we show that keratin genes play an essential role in spatial organization of other lineage-specific genes in keratinocytes during epidermal development. In fact, ablation of keratin type II locus from chromosome 15 in epidermal keratinocytes led to changes in the genomic organization with increased distance between the Loricrin gene located on chromosome 3 as well as between Satb1 gene located on chromosome 17 and keratin type II locus, resulting in a more peripheral localization of these genes in the nucleus. As a possible consequence of their peripheral localization, reduced expression of Loricrin and Satb1 has also been observed in keratins type II-deficient mice. These findings together with recent circularized chromosome conformation capture (4C) data, strongly suggest that keratin 5, Loricrin and Satb1 are part of the same interactome, which is required for the proper expression of these genes and proper epidermal development and epidermal barrier formation. Taken together these data suggest that higher order chromatin remodelling and spatial organization of genes in the nucleus are important for the establishment of lineage-specific differentiation programs in epidermal progenitor cells. These data provide an important background for further analyses of nuclear architecture in the alterations of epidermal differentiation, seen in pathological conditions, such as psoriasis and epithelial skin cancers.

Thesis (M. Phil.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xii, 152 p. : ill., (some col.). Includes abstract and vita. Advisor: Anthony Young, Molecular, Cellular, and Developmental Biology Program. Includes bibliographical references (p. 137-150).

Thesis (Ph.D.)--McMaster University, 2005. / Supervisor: Suleiman Igdoura. Includes bibliographical references (leaves 207-240). Also available online.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2007. / Additional advisors: Susan Bellis, Vladimir Fast, Chi-Tsou Huang, Donald Muccio. Description based on contents viewed June 23, 2009; title from PDF t.p. Includes bibliographical references.