No description available.

Graduation date: 1999

abstract / Pathology / Doctoral / Doctor of Philosophy

Histone proteins were examined during development in the meiotic elongate and a genetically close line N6HT. Histones were also extracted from an F1 (el x N6Ht). Comparisonc beteen the histone samples from each line of N6HT and elongate, and the F1 for leaf, root, and stem were inconclusive. A tassel sample form elongate exhibited a markedly slower migrating band that was not present in N6HT. The histone profiles of elongate and N6HT also differed. Each line N6HT and elongate exhibited three protein bands in the H1 region. Maize histone samples have been shown to exhibit four major H1 bands. The possibility exists that an H1 protein altered in its molecular weight and possibly in its interaction with the chromosome is present in elongate.

Thesis (Ph.D.)--University of Wyoming, 2008. / Title from PDF title page (viewed on June 24, 2009). Includes bibliographical references.

Thesis (Ph. D.)--University of Oklahoma. / Bibliography: leaves 118-130.

Positioning of nucleosomes within the 30nm fiber is fundamental in understanding how DNA compaction regulates gene expression. Numerous studies have focused on determining the structure, however; no studies have assessed the structure genome-wide. In this study, a new in silico methodology for genome-wide nucleosome arrangement was assessed through the use of randomly generating in silico datasets for the solenoid, solenoid-interdigitated, cross-linker (with odd and even n), twisted ribbon, and twisted ribbon-interdigitated. A PERL script was written to generate six in silico datasets from the human genome based on patterns and probabilities of close proximity nucleosomes, and align various length terminal ends of the sequences to the genome. A graphical representation was used to assess the genome-wide pattern of paired sequence alignments for each model. Whole genome sequence data from formaldehyde fixed HeLa cells were filtered, aligned, and compared to the models. Lack of sufficient experimental alignments yielded inconclusive model determination. / DNA compaction and the 30nm chromatin fiber -- Development of in silico method for analysis of the 30nm fiber on a genome-wide scale -- Experimental analysis of the 30nm chromatin fiber on a genome-wide scale -- Future directions. / Department of Biology

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains vii, 124 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 116-124).

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 5 uppsatser.

Eukaryotic DNA is incorporated into the nucleoprotein structure of chromatin. This structure is essential for the proper storage, maintenance, regulation, and function of the genomes’ constituent genes and genomic sequences. Importantly, cells generate discrete types of chromatin that impart distinct properties on genomic loci; euchromatin is an open and active compartment of the genome, and heterochromatin is a restricted and inactive compartment. Heterochromatin serves many purposes in vivo, from heritably silencing key gene loci during embryonic development, to preventing aberrant DNA repeat recombination. Despite this generally repressive role, the DNA contained within heterochromatin must still be repaired and replicated, creating a need for regulated dynamic access into silent heterochromatin. In this work, we discover and characterize activities that the ATP-dependent chromatin remodeling enzyme SWI/SNF uses to disrupt repressive heterochromatin structure. First, we find two specific physical interactions between the SWI/SNF core subunit Swi2p and the heterochromatin structural protein Sir3p. We find that disrupting these physical interactions results in a SWI/SNF complex that can hydrolyze ATP and slide nucleosomes like normal, but is defective in its ability to evict Sir3p off of heterochromatin. In vivo, we find that this Sir3p eviction activity is required for proper DNA replication, and for establishment of silent chromatin, but not for SWI/SNF’s traditional roles in transcription. These data establish new roles for ATP-dependent chromatin remodeling in regulating heterochromatin. Second, we discover that SWI/SNF can disrupt heterochromatin structures that contain all three Sir proteins: Sir2p, Sir3p and Sir4p. This new disruption activity requires nucleosomal contacts that are essential for silent chromatin formation in vivo. We find that SWI/SNF evicts all three heterochromatin proteins off of chromatin. Surprisingly, we also find that the presence of Sir2p and Sir4p on chromatin stimulates SWI/SNF to evict histone proteins H2A and H2B from nucleosomes. Apart from discovering a new potential mechanism of heterochromatin dynamics, these data also establish a new paradigm of chromatin remodeling enzyme regulation by nonhistone proteins present on the substrate.